CWT Bibliography

Journal Articles

Demi, LM, Benstead, JP, Rosemond, AD, Maerz, JC. Experimental N and P additions alter stream macroinvertebrate community composition via taxon-level responses to shifts in detrital resource stoichiometry. Funct Ecol. 2019; 00: 1– 13. https://doi.org/10.1111/1365-2435.13289

Abstract
1. Increases in nitrogen (N) and phosphorus (P) availability are changing animal communities, partly by altering stoichiometric imbalances between consumers and their food. Testing relationships between resource stoichiometry and consumer assemblage structure requires ecosystem-level manipulations that have been lacking to date. 2. We analysed patterns of macroinvertebrate community composition in five detritus- based headwater streams subject to experimental whole-stream N and P additions that spanned a steep gradient in dissolved N:P ratio (2:1, 8:1, 16:1, 32:1, 128:1) over 2 years, following a 1-year pre-treatment period. 3. We predicted that shifts in leaf litter stoichiometry would drive overall patterns of community composition via greater responses of shredders to enrichment than other taxa, as shredders dominate primary consumer biomass and experience larger consumer–resource elemental imbalances than other functional groups in stream ecosystems. Specifically, we expected litter C:P to be a significant predictor of shredder biomass given the greater relative imbalances between shredder and litter C:P than C:N. Finally, we tested whether shredder responses to enrichment were related to other taxon-level traits, including body size and stoichiometry, larval life span and growth rate. 4. Whole-community composition shifted similarly across the five streams after enrichment, largely driven by increased shredder and predator biomass. These shifts were limited to the autumn/winter seasons and related to decreased leaf litter C:P, highlighting important links between the quality of seasonal litter subsidies and community phenology. 5. Among 10 taxa that drove structural shifts, two declined while other taxa from the same functional/taxonomic groups responded positively, suggesting that specific life-history traits may determine sensitivity to enrichment. 6. Increases in total shredder biomass, and in biomass of several common shredders, were associated with lower litter C:P. Body C:P did not predict shredder response to enrichment. However, weak negative relationships between shredder response and body size, and larval life span, suggest that small-bodied and short-lived taxa may be more responsive to shifting resource stoichiometry.

Dharmadi, Sandra N., Elliott, Katherine J., Miniat, Chelcy F. (2019) Lack of forest tree seedling recruitment and enhanced tree and shrub growth characterizes post-Tsuga canadensis mortality forests in the southern Appalachians, Forest Ecology and Management. Forest Ecology and Management, 440:122-130, https://doi.org/10.1016/j.foreco.2019.03.024

Abstract
The loss of Tsuga canadensis from invasion by hemlock woolly adelgid (Adelges tsugae, HWA) has altered ecosystem structure and function in forests across the eastern United States. In southern Appalachian forests, T. canadensis co-occurred with hardwood species and an evergreen Rhododendron maximum shrub layer in riparian and cove positions. In this region, HWA infestation was detected in 2003, with mortality reaching 97% by 2014. In this study we examined responses of light, soil moisture, tree seedling density, and overstory and understory vegetation growth from 2004 to 2014 following HWA infestation and mortality of T. canadensis. We hypothesized that seedling recruitment and vegetation growth would continue to increase over time as observed with initial trends reported through 2009, and that species that associate with ectomycorrhizal (ECM) fungi may benefit more than those that do not due to the pulse of organic material in these stands from dead T. canadensis trees. Light transmission measured at 1m above the ground increased from 2006 to 2009, but gradually decreased from 2015 to 2017. Basal area of overstory non-Tsuga trees increased only marginally, and there was no recruitment of tree seedlings to the overstory size class, even though seedling density of deciduous species increased initially. Increased basal area and stem density of R. maximum may explain the light and seedling responses, as this species can inhibit tree seedling recruitment by limiting light and nutrients. Overstory species with the highest basal area increment (BAI) in the post-T. canadensis stands were Pinus rigida, Betula lenta and Quercus coccinea, which all associate with ECM fungi. However, not all ECM tree species grew significantly more following T. canadensis mortality compared to pre-mortality growth rates—only those ECM species that had high growth rates prior to mortality did. After a decade, growth of both overstory trees and R. maximum has not compensated for the loss of T. canadensis. Active management of R. maximum, which may involve the removal of the evergreen shrub and soil organic layer, may be required to allow for diverse tree seedling recruitment; and subsequently, restore riparian forest structure, diversity, and function.

Martin Tsz-Ki Tsui, Songnian Liu, Rebecka L. Brasso, Joel D. Blum, Sae Yun Kwon, Yener Ulus, Yabing H. Nollet, Steven J. Balogh, Sue L. Eggert, and Jacques C. Finlay. 2019. Controls of Methylmercury Bioaccumulation in Forest Floor Food Webs. Environmental Science & Technology. 53 (5), 2434-2440. DOI: 10.1021/acs.est.8b06053

Abstract
Compared to the extensive research on aquatic ecosystems, very little is known about the sources and trophic transfer of methylmercury (MeHg) in terrestrial ecosystems. In this study, we examine energy flow and trophic structure using stable carbon (d13C) and nitrogen (d15N) isotope ratios, respectively, and MeHg levels in basal resources and terrestrial invertebrates from four temperate forest ecosystems. We show that MeHg levels in biota increased significantly (p < 0.01) with d13C and d15N at all sites, implying the importance of both microbially processed diets (with increased d13C) and trophic level (with increased d15N) at which organisms feed, on MeHg levels in forest floor biota. The trophic magnification slopes of MeHg (defined as the slope of log10MeHg vs d15N) for these forest floor food webs (0.20-0.28) were not significantly different (p > 0.05) from those observed for diverse temperate freshwater systems (0.24 ± 0.07; n = 78), demonstrating for the first time the nearly equivalent efficiencies with which MeHg moves up the food chain in these contrasting ecosystem types. Our results suggest that in situ production of MeHg within the forest floor and efficient biomagnification both elevate MeHg levels in carnivorous invertebrates in temperate forests, which can contribute to significant bioaccumulation of this neurotoxin in terrestrial apex predators.

Amos, H.M., C.F. Miniat, J. Lynch, J. Compton, P.H. Templer, L.A. Sprague, D. Shaw, D. Burns, A. Rea, D. Whitfall, L. Myles, D. Gay, M. Nilles, J. Walker, A.K. Rose, J. Bales, J. Deacon, and R. Pouyat. 2018. What Goes Up Must Come Down: Integrating Air and Water Quality Monitoring for Nutrients. Environmental Science & Technology 52(20): pp 11441-11448.

Abstract
Excess nitrogen and phosphorus (“nutrients”) loadings continue to affect ecosystem function and human health across the U.S. Our ability to connect atmospheric inputs of nutrients to aquatic end points remains limited due to uncoupled air and water quality monitoring. Where connections exist, the information provides insights about source apportionment, trends, risk to sensitive ecosystems, and efficacy of pollution reduction efforts. We examine several issues driving the need for better integrated monitoring, including: coastal eutrophication, urban hotspots of deposition, a shift from oxidized to reduced nitrogen deposition, and the disappearance of pristine lakes. Successful coordination requires consistent data reporting; collocating deposition and water quality monitoring; improving phosphorus deposition measurements; and filling coverage gaps in urban corridors, agricultural areas, undeveloped watersheds, and coastal zones.

Berdanier, A. B. and Clark, J. S. (2018), Tree water balance drives temperate forest responses to drought. Ecology, 99: 2506-2514. doi:10.1002/ecy.2499

Abstract
Intensifying drought is increasingly linked to global forest diebacks. Improved understanding of drought impacts on individual trees has provided limited insight into drought vulnerability in part because tree moisture access and depletion is difficult to quantify. In forests, moisture reservoir depletion occurs through water use by the trees themselves. Here, we show that drought impacts on tree fitness and demographic performance can be predicted by tracking the moisture reservoir available to trees as a mass balance, estimated in a hierarchical state-space framework. We apply this model to multiple seasonal droughts with tree transpiration measurements to demonstrate how species and size differences modulate moisture availability across landscapes. The depletion of individual moisture reservoirs can be tracked over the course of droughts and linked to biomass growth and reproductive output. This mass balance approach can predict individual moisture deficit, tree demographic performance, and drought vulnerability throughout forest stands based on measurements from a sample of trees.

Bolstad, P. V., K. J. Elliott, and C. F. Miniat. 2018. Forests, shrubs, and terrain: top-down and bottom-up controls on forest structure. Ecosphere 9(4):e02185. 10.1002/ecs2.2185

Abstract
Overstory forest structure responds to terrain-related abiotic factors and to biotic interactions among overstory and understory plants. Unlike species abundance, tree height, biomass, and leaf area in many regions have been poorly quantified in relation to terrain-driven environmental gradients. In addition, the magnitude of understory influences on overstory structure has been poorly characterized for many forest systems. Our primary goal was to identify relationships between terrain (elevation, convexity, exposure), evergreen understory, and overstory structure (height, aboveground biomass, leaf area) in mature deciduous forests of the southern Appalachian Mountains. We used a combination of field point and plot measurements, LiDAR, and satellite image data to sample little-disturbed deciduous forest stands. Height, biomass, and gap frequency were significantly related to changes in elevation, exposure (aspect), and convexity (cove to ridge). Higher evergreen understory density was strongly correlated with decreases in forest height and biomass, with an impact observed across moisture, elevation, and exposure gradients. Canopies on ridges averaged half as tall at the highest evergreen understory densities when compared to those without evergreen shrubs (10 vs. 19 m), and overstory canopy height averaged 6 m shorter on sideslopes with high evergreen understory density compared to those with low evergreen understory density. Canopy height declined from low to high elevations, with larger relative decreases on ridges, but biomass increased from low to high elevations, due primarily to high biomass in coves at mid- to upper elevations. Biomass and canopy height declined from cove to ridge and north- to south-facing slopes. Responses in canopy height and aboveground biomass associated with changes in understory evergreen density were similar to impacts due to terrain. Gaps were more frequent on south-facing slopes. Previous studies at this site and others identify soil moisture and soil N competition as the most plausible mechanisms by which understory shrubs might influence overstory canopy structure, with low light limiting seedling recruitment as an additional mechanism. Our work suggests evergreen understory density, particularly on sideslope and ridge locations, substantially affects overstory canopy height and biomass.

Cecala, K. K., J. C. Maerz, B. J. Halstead, J. R. Frisch, T. L. Gragson, J. Hepinstall-Cymerman, D. S. Leigh, C. R. Jackson, J. T. Peterson, and C. M. Pringle. 2018. Multiple drivers, scales, and interactions influence southern Appalachian stream salamander occupancy. Ecosphere 9(3):e02150. 10.1002/ecs2.2150

Abstract
Understanding how factors that vary in spatial scale relate to population abundance is vital to forecasting species responses to environmental change. Stream and river ecosystems are inherently hierarchical, potentially resulting in organismal responses to fine-scale changes in patch characteristics that are conditional on the watershed context. Here, we address how populations of two salamander species are affected by interactions among hierarchical processes operating at different scales within a rapidly changing landscape of the southern Appalachian Mountains. We modeled reach-level occupancy of larval and adult black-bellied salamanders (Desmognathus quadramaculatus) and larval Blue Ridge two-lined salamanders (Eurycea wilderae) as a function of 17 different terrestrial and aquatic predictor variables that varied in spatial extent. We found that salamander occurrence varied widely among streams within fully forested catchments, but also exhibited species-specific responses to changes in local conditions. While D. quadramaculatus declined predictably in relation to losses in forest cover, larval occupancy exhibited the strongest negative response to forest loss as well as decreases in elevation. Conversely, occupancy of E. wilderae was unassociated with watershed conditions, only responding negatively to higher proportions of fast-flowing stream habitat types. Evaluation of hierarchical relationships demonstrated that most fine-scale variables were closely correlated with broad watershed-scale variables, suggesting that local reach-scale factors have relatively smaller effects within the context of the larger landscape. Our results imply that effective management of southern Appalachian stream salamanders must first focus on the larger scale condition of watersheds before management of local-scale conditions should proceed. Our findings confirm the results of some studies while refuting the results of others, which may indicate that prescriptive recommendations for range-wide management of species or the application of a single management focus across large geographic areas is inappropriate.

Chandler, Richard B., Hepinstall-Cymerman, Jeff, Merker, Samuel, Abernathy-Conners, Heather, Cooper, Robert J. (2018). Characterizing spatio-Temporal variation in survival and recruitment with integrated population models. The Auk. 135. 409-426. 10.1642/AUK-17-181.1.

Abstract
Efforts to understand population dynamics and identify high-quality habitat require information about spatial variation in demographic parameters. However, estimating demographic parameters typically requires labor-intensive capture-recapture methods that are difficult to implement over large spatial extents. Spatially explicit integrated population models (IPMs) provide a solution by accommodating spatial capture-recapture (SCR) data collected at a small number of sites with survey data that may be collected over a much larger extent. We extended the spatial IPM framework to include a spatio-Temporal point process model for recruitment, and we applied the model to 4 yr of SCR and distance-sampling data on Canada Warblers (Cardellina canadensis) near the southern extent of the species' breeding range in North Carolina, USA, where climate change is predicted to cause population declines and distributional shifts toward higher elevations. To characterize spatial variation in demographic parameters over the climate gradient in our study area, we modeled density, survival, and per capita recruitment as functions of elevation. We used a male-only model because males comprised >90% of our point-count detections. Apparent survival was low but increased with elevation, from 0.040 (95% credible interval CI: 0.0032-0.12) at 900 m to 0.29 (95% CI: 0.16-0.42) at 1,500 m. Recruitment was not strongly associated with elevation, yet density varied greatly, from <0.03 males ha?¹ below 1,000 m to >0.2 males ha?¹ above 1,400 m. Point estimates of population growth rate were <1 at all elevations, but 95% CIs included 1. Additional research is needed to assess the possibility of a long-Term decline and to examine the effects of abiotic variables and biotic interactions on the demographic parameters influencing the species' distribution. The modeling framework developed here provides a platform for addressing these issues and advancing knowledge about spatial demography and population dynamics.

Cofer, T. M., K. J. Elliott, J. K. Bush, and C. F. Miniat. 2018. Rhododendron maximum impacts seed bank composition and richness following Tsuga canadensis loss in riparian forests. Ecosphere 9(4):e02204. 10.1002/ecs2.2204

Abstract
Southern Appalachian riparian forests have undergone changes in composition and function from invasive pathogens and pests. Castanea dentata mortality in the 1930s from chestnut blight (Cryphonectria parasitica) and Tsuga canadensis mortality in the 2000s from the hemlock woolly adelgid (Adelges tsugae) have led to the expansion and increased growth of Rhododendron maximum, an evergreen subcanopy shrub. A better understanding of seed bank characteristics and the various abiotic and biotic factors that affect the seed bank may be useful in determining the restoration potential of forest communities following invasion-related disturbances. We compared the seed bank of two deciduous forest types: hardwood forests with a dense R. maximum subcanopy (hereafter, RR) and hardwood forests without R. maximum (hereafter, HWD). We evaluated numerous microenvironmental variables through principal component analysis (PCA) and correlated the derived PCA axes scores to seed bank density and richness across forest types. We found that seed bank density was comparable between the forests types; however, seed bank richness was much lower in RR than HWD and the species composition was dissimilar between forest types. Twenty-eight of 64 (44%) species in the seed bank of HWD were not found in the seed bank of RR. Species that were represented in both forest types were often found in contrasting densities. Most notably, seed bank densities of several woody species were considerably higher in RR (85%) than HWD (45%), while herbaceous seed bank density was lower in RR (11%) than HWD (50%). Mineral soil pH, soil nutrient availability, and soil moisture were lower, and organic soil (Oi + Oe + Oa) depth and mass were greater in the RR than HWD forest type. PCA correlations revealed that PCA4 (represented by understory density and Oe + Oa phosphorus and carbon/nitrogen ratio) was negatively correlated with total seed bank density. PCA1 (represented by Oe + Oa cations and phosphorus, understory richness, ground-layer cover, and mineral soil pH) and PCA4 were positively correlated with total seed bank richness. These results suggest that the soil seed bank will not be the primary mode of recruitment to establish a diverse and herbaceous-rich community if a RR is present.

Demi, L.M., J.P. Benstead, A.D. Rosemond, and J.C. Maerz. 2018. Litter P content drives consumer production in detritus-based streams spanning an experimental N:P gradient. Ecology. 99:347-359. 10.1002/ecy.2118

Abstract
Ecological stoichiometry theory (EST) is a key framework for predicting how variation in N:P supply ratios influences biological processes, at molecular to ecosystem scales, by altering the availability of C, N, and P relative to organismal requirements. We tested EST predictions by fertilizing five forest streams at different dissolved molar N:P ratios (2, 8, 16, 32, 128) for two years and tracking responses of macroinvertebrate consumers to the resulting steep experimental gradient in basal resource stoichiometry (leaf litter %N, %P, and N:P). Nitrogen and P content of leaf litter, the dominant basal resource, increased in all five streams following enrichment, with steepest responses in litter %P and N:P ratio. Additionally, increases in primary consumer biomass and production occurred in all five streams following N and P enrichment (averages across all streams: biomass by 1.2×, production by 1.6×). Patterns of both biomass and production were best predicted by leaf litter N:P and %P and were unrelated to leaf litter %N. Primary consumer production increased most in streams where decreases in leaf litter N:P were largest. Macroinvertebrate predator biomass and production were also strongly positively related to litter %P, providing robust experimental evidence for the primacy of P limitation at multiple trophic levels in these ecosystems. However, production of predatory macroinvertebrates was not related directly to primary consumer production, suggesting the importance of additional controls for macroinvertebrates at upper trophic positions. Our results reveal potential drivers of animal production in detritus-based ecosystems, including the relative importance of resource quality vs. quantity. Our study also sheds light on the more general impacts of variation in N:P supply ratio on nutrient-poor ecosystems, providing strong empirical support for predictions that nutrient enrichment increases food web productivity whenever large elemental imbalances between basal resources and consumer demand are reduced.

Dornelas M, Antão LH, Moyes F, et al. BioTIME: A database of biodiversity time series for the Anthropocene. Global Ecol Biogeogr. 2018; 00:1 - 26. https://doi.org/10.1111/geb.12729

Abstract
The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene. The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record. BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2). BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year. BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

Elliott, K.J. & Miniat, Chelcy. (2018). Herbaceous-layer diversity and tree seedling recruitment are enhanced following Rhododendron maximum shrub removal. Forest Ecology and Management. 430. 403-412. 10.1016/j.foreco.2018.08.016.

Abstract
Forest ecosystems dominated by Tsuga canadensis are undergoing fundamental changes in function and composition from infestations by hemlock woolly adelgid (Adelges tsugae). We proposed that the first step to restoring southern Appalachian riparian forests following T. canadensis mortality would be eliminating the evergreen shrub, Rhododendron maximum. We hypothesized that removing R. maximum would increase light transmittance, soil moisture and temperature; and subsequently, enhance herbaceous-layer diversity and promote tree seedling recruitment and survival. We tested these hypotheses at two locations, (CWT, Coweeta Hydrologic Laboratory; WOC, White Oak Creek) in the Nantahala Mountain Range of western North Carolina, both with heavy T. canadensis mortality and a dense R. maximum subcanopy. The treatments were designed to remove only soil Ohorizon (FF), remove only R. maximum (CR), remove R. maximum and soil O-horizon (CFFR), and untreated, reference (REF). We installed permanent plots across treatments and locations and measured light transmittance (Qi/Qo), soil water content (?), herbaceous-layer cover and diversity (Shannon’s index (H'cover) and species richness), and tree seedling recruitment. As expected, cutting the R. maximum subcanopy (CR and CFFR) immediately increased Qi/Qo in the spring months across locations, and it was sustained through the first growing season. ? was generally high across plots, averaging 26% during the growing season, and didn’t vary over time. By the second growing season (2017) after treatments, herbaceous-layer cover and diversity increased on CR and CFFR. Herbaceous-layer cover was significantly related to Qi/Qo (r2=0.22, p < 0.001) and ? (r2=0.13, p=0.009), while diversity was only related to Qi/Qo (H'cover, r2=0.14, p < 0.001; species richness, r2=0.21, p < 0.001). Tree seedling density was related to Qi/Qo (r2=0.10, p=0.001) and ? (r2=0.26, p < 0.001). Tree seedling density was low before treatment (1.4 ± 0.3 seedlings m-2) and increased by 10-fold in CR and CFFR two growing seasons after treatment. In CR, species with the highest density ranked Betula spp. > Acer rubrum > Quercus coccinea > Liriodendron tulipifera > Q. rubra. In CFFR, tree seedling recruitment ranked Betula spp. > A. rubrum > L. tulipifera. These vegetation responses have important implications for potential recovery of riparian forests following T. canadensis mortality.

Farrell, K.J., A.D. Rosemond, J.S. Kominoski, S.M. Bonjour, J. Rüegg, L.E. Koenig, C.L. Baker, M.T. Trentman, T.K. Harms, W.H. McDowell. 2018. Variation in detrital resource stoichiometry signals differential carbon to nutrient limitation for stream consumers across biomes. Ecosystems. 21: 1676-1691.

Abstract
Stoichiometric ratios of resources and consumers have been used to predict nutrient limitation across diverse terrestrial and aquatic ecosystems. In forested headwater streams, coarse and fine benthic organic matter (CBOM, FBOM) are primary basal resources for the food web, and the distribution and quality of these organic matter resources may therefore influence patterns of secondary production and nutrient cycling within stream networks or among biomes. We measured carbon (C), nitrogen (N), and phosphorus (P) content of CBOM and FBOM and calculated their stoichiometric ratios (C/N, C/P, N/P) from first- to fourth-order streams from tropical montane, temperate deciduous, and boreal forests, and tallgrass prairie, to compare the magnitude and variability of these resource types among biomes. We then used the ratios to predict nutritional limitations for consumers of each resource type. Across biomes, CBOM had consistently higher %C and %N, and higher and more variable C/N and C/P than FBOM, suggesting that microbial processing results in more tightly constrained elemental composition in FBOM than in CBOM. Biome-specific differences were observed in %P and N/P between the two resource pools; CBOM was lower in %P but higher in N/P than FBOM in the tropical montane and temperate deciduous forest biomes, while CBOM was higher in %P but similar in N/P than FBOM in the grassland and boreal forest biomes. Stable 13C isotopes suggest that FBOM likely derives from CBOM in tropical and temperate deciduous forest, but that additional non-detrital components may contribute to FBOM in boreal forests and grasslands. Comparisons of stoichiometric ratios of CBOM and FBOM to estimated needs of aquatic detritivores suggest that shredders feeding on CBOM are more likely to experience nutrient (N and/or P) than C limitation, whereas collector–gatherers consuming FBOM are more likely to experience C than N and/or P limitation. Our results suggest that differences in basal resource elemental content and stoichiometric ratios have the potential to affect consumer production and ecosystem rates of C, N, and P cycling in relatively consistent ways across diverse biomes.

Fraterrigo, J. M., Ream, K., & Knoepp, J. D. (2018). Tree mortality from insect infestation enhances carbon stabilization in southern Appalachian forest soils. Journal of Geophysical Research: Biogeosciences, 123, 2121–2134. https://doi.org/10.1029/2018JG004431

Abstract
Forest insect and pathogen outbreaks may exacerbate anthropogenic climate change if they accelerate soil carbon loss to the atmosphere. We quantified soil respiration and carbon content for nearly a decade after girdling or natural infestation of hemlock (Tsuga canadensis L. Carr., a codominant species in southern Appalachian forests) by hemlock woolly adelgid (Adelges tsugae) to improve understanding of soil carbon response to disturbance from forest insect and pathogens. From 2005 to 2013, net soil respiration was similar among hemlock mortality (~50% basal area reduction) and reference hardwood plots, but both girdled and hemlock woolly adelgid-infested plots showed greater activities of ß-glucosidase (a cellulose-hydrolyzing extracellular enzyme), decreased O-horizon, and decreased fine root biomass. During this period, mineral soil carbon accumulated at a higher rate in hemlock mortality plots than in reference plots in both surface (0–10 cm) and subsurface (10–30 cm) soils, driven by increases in the mineral-associated fraction of the soil organic matter. In contrast, particulate organic matter (POM) carbon accrued slowly in surface soils and declined in the subsurface of girdled plots. d13C values of the POM fraction demonstrate increased microbial processing of surface soil organic matter over time, suggesting enhanced decomposition of organic matter in this pool. These findings indicate that hemlock mortality in this system has led to enhanced soil carbon stabilization through the transformation and translocation of carbon from detrital and POM pools to the mineral-associated organic matter pool. Accelerated responses in the girdled versus naturally infested treatments highlight limitations associated with using girdling to simulate natural mortality.

Klaus, J., & Jackson, C. R. (2018). Interflow is not binary: A continuous shallow perched layer does not imply continuous connectivity. Water Resources Research, 54. https://doi.org/10.1029/2018WR022920

Abstract
Hillslopes exert critical controls on the quality and quantity of downstream waters. To understand and model dominant headwater catchment processes, we need to estimate the relative importance of different runoff generation processes. In this work we analyze published data from studies of 17 hillslopes from a range of landscapes to better understand the relative role of interflow, that is, shallow lateral subsurface flow moving over a layer impeding percolation, in streamflow generation. For each slope, we calculated downslope interflow travel distances, that is, the potential distance a water parcel travels downslope above an impeding layer until it percolates into the impeding layer. The downslope travel distances for the 17 hillslopes ranged from around 1 m to several hundred meters. The vector analysis of downslope travel distances revealed that all but three hillslopes had slope lengths that were much longer than downslope travel distances. For the remaining 14 cases we could show that most water perched above a shallow impeding layer percolates through the impeding layer before reaching the valley or the stream channel. Thus, interflow usually contributes directly to valley water or streamflow only from the lower portions of the hillslope in most landscapes. A critical finding of our analysis is that a continuously perched saturated zone with downslope flow does not imply continuous connectivity to the stream. Such a continuous connectivity is the exception rather than the rule in most landscapes. Future hillslope and headwater processes and modeling studies will need to account for this.

Knoepp, Jennifer D.; See, Craig R.; Vose, James M.; Miniat, Chelcy F.; and Clark, James S. 2018. Total C and N Pools and Fluxes Vary with Time, Soil Temperature, and Moisture Along an Elevation, Precipitation, and Vegetation Gradient in Southern Appalachian Forests. Ecosystems. DOI: 10.1007/s10021-018-0244-2

Abstract
The interactions of terrestrial C pools and fluxes with spatial and temporal variation in climate are not well understood. We conducted this study in the southern Appalachian Mountains where complex topography provides variability in temperature, precipitation, and forest communities. In 1990, we established five large plots across an elevation gradient allowing us to study the regulation of C and N pools and cycling by temperature and water, in reference watersheds in Coweeta Hydrologic Laboratory, a USDA Forest Service Experimental Forest, in western NC, USA. Communities included mixed-oak pine, mixed-oak, cove hardwood, and northern hardwood. We examined 20-year changes in overstory productivity and biomass, leaf litterfall C and N fluxes, and total C and N pools in organic and surface mineral soil horizons, and coarse wood, and relationships with growing season soil temperature and precipitation. Productivity increased over time and with precipitation. Litterfall C and N flux increased over time and with increasing temperature and precipitation, respectively. Organic horizon C and N did not change over time and were not correlated to litterfall inputs. Mineral soil C and N did not change over time, and the negative effect of temperature on soil pools was evident across the gradient. Our data show that increasing temperature and variability in precipitation will result in altered aboveground productivity. Variation in surface soil C and N is related to topographic variation in temperature which is confounded with vegetation community. Data suggest that climatic changes will result in altered aboveground and soil C and N sequestration and fluxes.

McDonald, J.M., D.S. Leigh, and C.R. Jackson. 2018. Continental-, Watershed-, and Local-Scale Influences on Winter Stormflow Characteristics in the Southern Blue Ridge Mountains of Western North Carolina. Journal of Hydrology 563:643-656. https://doi.org/10.1016/j.jhydrol.2018.06.013

Abstract
Spatial and temporal influences on the winter (December-March) stormflow characteristics of fifteen United States Geological Survey (USGS)-gaged watersheds in the Southern Blue Ridge Mountains are identified: (1) watershed-scale differences in geomorphology; (2) continental-scale teleconnections during periods of wetness/dryness (based on the relative amount of winter precipitation over a consistent 20?year dataset); and (3) land cover in the context of soil parent material (e.g., development on alluvium/colluvium). Multiple regression was used to determine how much variance could be explained in five hydrologic variables describing the flashiness of peak flow (three original metrics), total seasonal flashiness (Richards Baker flashiness index), and the ratio of total winter stormflow to total discharge (the stormflow index). Models were constrained to three uncorrelated (|0.65|) variables to prevent overfitting to the dataset. Average-, dry-, and wet-years were subset using the z-scores for winter precipitation derived from the 4?km monthly PRISM (Parameter-elevation Relationships on Independent Slopes Model) dataset, for the period of 1986–2006. Relief, slope, and landscape connectivity explain the majority of explained variance in all five of the hydrologic variables during all time periods. During dry-, average-, and wet-years, atmospheric circulation patterns (i.e., North Atlantic Oscillation and Pacific/North American Pattern) explain more variance than total seasonal precipitation (PRISM), which is not true in the majority of the all-years models. Land cover explains only a small portion of the variance in regional stormflow and only when sub-divided based on soil parent material. Results provide a framework for connecting watershed-scale characteristics to regional- and continental-scale processes.

McDonnell JJ, J. Evaristo, K. Bladon, J. Buttle, I. Creed, S. Dymond, G. Grant, A. Iroume, C.R Jackson, J. Jones, T. Maness, K. McGuire, D. Scott, C. Segura, R. Sidle, and C. Tague. 2018. Water sustainability and watershed storage, Commentary. Nature Sustainability 1:378-379. doi:10.1038/s41893-018-0099-8

Abstract
The paired watershed approach is the most popular tool for quantifying the effects of forest watershed management on water sustainability. But this approach does not often address the critical factor of water stored in the landscape. Future work needs to quantify storage in paired watershed studies to inform sustainable water management.

Oishi, A.C. & Miniat, C.F. & Novick, K.A. & Brantley, Steven & Vose, James & Walker, John. 2018. Warmer temperatures reduce net carbon uptake, but do not affect water use, in a mature southern Appalachian forest. Agricultural and Forest Meteorology. 252. 269-282. 10.1016/j.agrformet.2018.01.011.

Abstract
Increasing air temperature is expected to extend growing season length in temperate, broadleaf forests, leading to potential increases in evapotranspiration and net carbon uptake. However, other key processes affecting water and carbon cycles are also highly temperature-dependent. Warmer temperatures may result in higher ecosystem carbon loss through respiration and higher potential evapotranspiration through increased atmospheric demand for water. Thus, the net effects of a warming planet are uncertain and highly dependent on local climate and vegetation. We analyzed five years of data from the Coweeta eddy covariance tower in the southern Appalachian Mountains of western North Carolina, USA, a highly productive region that has historically been underrepresented in flux observation networks. We examined how leaf phenology and climate affect water and carbon cycling in a mature forest in one of the wettest biomes in North America. Warm temperatures in early 2012 caused leaf-out to occur two weeks earlier than in cooler years and led to higher seasonal carbon uptake. However, these warmer temperatures also drove higher winter ecosystem respiration, offsetting much of the springtime carbon gain. Interannual variability in net carbon uptake was high (147 to 364 g Cm-2 y-1), but unrelated to growing season length. Instead, years with warmer growing seasons had 10% higher respiration and sequestered ~40% less carbon than cooler years. In contrast, annual evapotranspiration was relatively consistent among years (coefficient of variation=4%) despite large differences in precipitation (17%, range=800 mm). Transpiration by the evergreen understory likely helped to compensate for phenologicallydriven differences in canopy transpiration. The increasing frequency of high summer temperatures is expected to have a greater effect on respiration than growing season length, reducing forest carbon storage.

Osburn, E.D., Elliottt, K.J., Knoepp, J.D., Miniat, C.F. and Barrett, J.E., 2018. Soil microbial response to Rhododendron understory removal in southern Appalachian forests: Effects on extracellular enzymes. Soil Biology and Biochemistry, 127, pp.50-59. 10.1016/j.soilbio.2018.09.008

Abstract
Rhododendron maximum is a native evergreen shrub that has expanded in Appalachian forests following declines of american chestnut (Castanea dentata) and eastern hemlock (Tsuga canadensis). R. maximum is of concern to forest managers because it suppresses hardwood tree establishment by limiting light and soil nutrient availability. We are testing R. maximum removal as a management strategy to promote recovery of Appalachian forests. We hypothesized that R. maximum removal would increase soil nitrogen (N) availability, resulting in increased microbial C-demand (i.e. increased C-acquiring enzyme activity) and a shift towards bacterial-dominated microbial communities. R. maximum removal treatments were applied in a 2?×?2 factorial design, with two R. maximum canopy removal levels (removed vs not) combined with two O-horizon removal levels (burned vs unburned). Following removals, we sampled soils and found that dissolved organic carbon (DOC), N (TDN, NO3, NH4), and microbial biomass all increased with R. maximum canopy + O-horizon removal. Additionally, we observed increases in C-acquisition enzymes involved in degrading cellulose (ß-glucosidase) and hemicellulose (ß-xylosidase) with canopy + O-horizon removal. We did not see treatment effects on bacterial dominance, though F:B ratios from all treatments increased from spring to summer. Our results show that R. maximum removal stimulates microbial activity by increasing soil C and N availability, which may influence recovery of forests in the Appalachian region.

Rice, J.L., and Burke, B.J. (2018) Building More Inclusive Solidarities for Socio- Environmental Change: Lessons in Resistance from Southern Appalachia. Antipode 50(1): 212-232. doi: 10.1111/anti.12336

Abstract
It is increasingly recognized that socio-environmental justice will not be achieved through liberal and cosmopolitical forms of activism alone. Instead, more diverse and inclusive solidarities must be achieved across political ideologies for transformative change. By engaging with one constituency often overlooked by mainstream environmentalists—rural, conservative Americans—we argue for a situated solidarity that can be forged among people whose views of nature, community, and politics differ significantly. This framework rejects totalizing expressions of global ambition that erase important place-based differences. To explore this ethic, we examine a localized anti-fracking campaign in western North Carolina to determine how place-based forms of environmental resistance can be brought in closer connection with the cosmopolitical movement for climate and energy justice. This requires that cosmopolitical movements make room for more customary forms of cultural politics, while conservative movements look beyond their own place-based struggles to resist mutually experienced forms of oppression.

Seyednasrollah, B., Swenson, J.L., Domec, J-C., Clark, J.S. (2018) Leaf phenology paradox: Why warming matters most where it is already warm. Remote Sensoing of Environment 209:446-455. https://doi.org/10.1016/j.rse.2018.02.059

Abstract
Interactions between climate and ecosystem properties that control phenological responses to climate warming and drought are poorly understood. To determine contributions from these interactions, we used space-borne remotely sensed vegetation indices to monitor leaf development across climate gradients and ecoregions in the southeastern United States. We quantified how air temperature, drought severity, and canopy thermal stress contribute to changes in leaf flushing from mountainous to coastal plain regions by developing a hierarchical state-space Bayesian model. We synthesized daily field climate data with daily vegetation indices and canopy surface temperature during spring green-up season at 59 sites in the southeastern United States between 2001 and 2012. Our results demonstrated strong interaction effects between ecosystem properties and climate variables across ecoregions. We found spring green-up is faster in the mountains, while coastal forests express a larger sensitivity to inter-annual temperature anomalies. Despite our detection of a decreasing trend in sensitivity to warming with temperature in all regions, we identified an ecosystem interaction: Deciduous dominated forests are less sensitive to warming than are those with fewer deciduous trees, likely due to the continuous presence of leaves in evergreen species throughout the season. Mountainous forest green-up is more susceptible to intensifying drought and moisture deficit, while coastal areas are relatively resilient. We found that with increasing canopy thermal stress, defined as canopy-air temperature difference, leaf development slows following dry years, and accelerates following wet years.

Singh, N. K., Emanuel, R. E., Nippgen, F., McGlynn, B. L., & Miniat, C. F. (2018). The relative influence of storm and landscape characteristics on shallow groundwater responses in forested headwater catchments. Water Resources Research, 54. https://doi.org/10.1029/2018WR022681

Abstract
Shallow groundwater responses to rainfall in forested headwaters can be highly variable, but their relative strengths of influences remain poorly understood. We investigated the roles of storms and landscape characteristics on short-term, shallow groundwater responses to rainfall in forested headwater catchments. We used field observations of shallow groundwater combined with random forest modeling to identify the factors that affect shallow groundwater responses and the relative influences of key response drivers. We found that the rainfall thresholds required for groundwater responses were only met by the largest quartile of events, suggesting that most events contributed to unsaturated soil storage or were lost to evaporation. Significantly higher rainfall thresholds and longer response times for south facing catchments as opposed to north facing catchments highlighted the role of insolation in setting antecedent conditions that influenced the groundwater response. During storms, there were significantly larger increases in water table height in catchments dominated by coniferous forests compared to deciduous forests, indicating that local spatial characteristics of hillslopes could be more important factors for groundwater response than catchment wetness. The random-forest analysis revealed that total rainfall amount had the greatest influence on most groundwater responses, but the relative influence of topography and local antecedent wetness was more pronounced as events progressed, indicating a shift in hydrological processes during different stages of the groundwater response. These results have implications for our understanding of runoff generation processes, including processes that determine hydrologic connectivity between stream and hillslopes.

Warren, R. J., Elliott, K. J., Giladi, I. , King, J. R. and Bradford, M. A. (2018), Field experiments show contradictory short- and long-term myrmecochorous plant impacts on seed-dispersing ants. Ecol Entomol. . doi:10.1111/een.12666

Abstract
1. Some interactions previously described as mutualistic were revealed to be commensal or parasitic in subsequent investigations. Ant-mediated seed dispersal has been described as a mutualism for more than a century; however, recent research suggests that it may be commensal or parasitic. Plants demonstrably benefit from ant-mediated seed dispersal, although there is little evidence available to demonstrate that the interaction benefits long-term ant fitness. 2. Field experiments were conducted in temperate North America focused on a key seed-dispersing ant. All herbaceous plants were removed from a forest understorey for 13 years, and supplemented ant colonies with large elaiosome-bearing seeds aiming to examine potential long- and short-term myrmecochorous plant benefits for the ants. 3. If elaiosome-bearing seeds benefit ants, suggesting a mutualistic relationship, it is expected that there would be greater worker and/or alate abundance and greater fat reserves (colony lipid content) with seed supplementation (short-term) and in areas with high understorey herb abundance. 4. Short-term seed supplementation of ant colonies did not result in an increase with respect to numbers or fat stores, although it did prompt the production of colony sexuals, which is a potential fitness benefit. In the long term, however, there was no positive effect on the ants and, instead, there were negative effects because the removal of elaiosome-bearing plants corresponded with greater colony health. 5. The data obtained in the present study suggest that the ant–plant interaction ranged from occasionally beneficial to neutral to overall negative for the ant partner. Such results did not support considering the interaction as a mutualism. Collectively, the data suggest the need to reconsider the nature of the relationship between these ants and plants.

Webster, Jackson R, Stewart, Rebecca M., Knoepp, Jennifer D., Jackson, C. Rhett (2018). Effects of instream processes, discharge, and land cover on nitrogen export from southern Appalachian Mountain catchments. Hydrological Processes. 10.1002/hyp.13325.

Abstract
Catchments with minimal disturbance usually have low dissolved inorganic nitrogen (DIN) export, but disturbances and anthropogenic inputs result in elevated DIN concentration and export and eutrophication of downstream ecosystems. We studied streams in the southern Appalachian Mountains, USA, an area dominated by hardwood deciduous forest but with areas of valley agriculture and increasing residential development. We collected weekly grab samples and storm samples from nine small catchments and three river sites. Most discharge occurred at baseflow, with baseflow indices ranging from 69% to 95%. We identified three seasonal patterns of baseflow DIN concentration. Streams in mostly forested catchments had low DIN with bimodal peaks, and summer peaks were greater than winter peaks. Streams with more agriculture and development also had bimodal peaks; however, winter peaks were the highest. In streams draining catchments with more residential development, DIN concentration had a single peak, greatest in winter and lowest in summer. Three methods for estimating DIN export produced consistent results. Annual DIN export ranged from less than 200 g ha-1 year-1 for the less disturbed catchments to over 2,000 g ha-1 year-1 in the catchments with the least forest area. Land cover was a strong predictor of DIN concentration but less significant for predicting DIN export. The two forested reference catchments appeared supply limited, the most residential catchment appeared transport limited, and export for the other catchments was significantly related to discharge. In all streams, baseflow DIN export exceeded stormflow export. Morphological and climatological variation among watersheds created complexities unexplainable by land cover. Nevertheless, regression models developed using land cover data from the small catchments reasonably predicted concentration and export for receiving rivers. Our results illustrate the complexity of mechanisms involved in DIN export in a region with a mosaic of climate, geology, topography, soils, vegetation, and past and present land use.

Zachary W. Anglin and Gary D. Grossman, 2018 Movement of Southern Brook Charr in a North Carolina Headwater Stream, Southeastern Naturalist 17 (3), 476-483, https://doi.org/10.1656/058.017.0314

Abstract
Little is known about the genetically distinct southern strain of Salvelinus fontinalis Mitchell (Brook Charr), a species that is likely to be negatively affected by global climate change at the southern extent of its range. We tagged 35 Southern Brook Charr between March and October of 2011 and sampled for movements in May and October 2011 and May 2012. The study site in Ball Creek, NC, was 330 m long, and we sampled 2 ancillary 50-m sites located 300 m above and below the site boundaries. We recaptured a total of 12 fish: 10 fish once, 1 fish twice, and another fish 3 times for a total of 15 recaptures. Individuals recaptured in spring 2011 moved an average of 9 m downstream, whereas fish recaptured in autumn 2011 moved an average of 7 m upstream. Fish recaptured in spring 2012 moved an average of 6 m upstream from their locations in autumn 2011. There was no relationship between fish length or growth and either distance or direction moved. In addition, there were no significant differences in length or mass of fish that were recaptured and those that were not. The maximum distance moved by a single fish was 49 m downstream. Our results suggest that Southern Brook Charr in headwater streams may have relatively small home ranges (<20 m), although our conclusions were limited by small sample sizes and a 34% recapture percentage based on individual fish. Given that most populations of Southern Brook Charr occur in small streams above barriers, limited movements suggest that population persistence will depend on satisfactory foraging, shelter, and reproductive habitat types within a relatively small area. These requirements should be a concern for managers given that global climate change will affect ambient temperatures and these populations have limited opportunity for movement and emigration.

Baas, Peter & Knoepp, J & Markewitz, Daniel & Mohan, Jacqueline. (2017). Areas of residential development in the southern Appalachian Mountains are characterized by low riparian zone nitrogen cycling and no increase in soil greenhouse gas emissions. Biogeochemistry. DOI:10.1007/s10533-017-0318-9.

Abstract
The critical role streamside riparian zones play in mitigating the movement of nitrogen (N) and other elements from terrestrial to aquatic ecosystems could be threatened by residential development in the southern Appalachian Mountains. Many studies have investigated the influence of agriculture on N loading to streams but less is known about the impacts of residential development. Here we consider the dynamics of changing riparian land use in the southern Appalachians that includes increased residential development at the expense of both forests and agriculture. We hypothesized that increased inputs of inorganic N from residential development will increase nitrogen cycling rates relative to forests, thereby preventing terrestrial N retention and increasing soil nitrate losses through leaching. In addition, we hypothesized that such development will increase emissions of N2O, CO2, and CH4, all potent greenhouse gases. We found riparian soil potential N cycling rates as well as N2O and CO2 efflux to be much greater with agricultural land use compared to either forested or residential land use. Our data suggest that residential development of forested riparian ecosystems does not increase N cycling or removal and, thus, might allow for greater potential N leaching into streams. Both agricultural and residential land use exhibited CH4 efflux while forested ecosystems were responsible for CH4 uptake. Overall, regional greenhouse gas emissions are projected to decline as high N2O and CO2 emitting agricultural land is converted to residential use.

Brantley, Steven T., Mayfield, Albert (Bud), Jetton, Robert M., Miniat, Chelcy F., Zietlow, David R.;, Brown, Cindi L., Rhea, Rusty (2017), Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings, Forest Ecology and Management, 386:150-160, http://dx.doi.org/10.1016/j.foreco.2016.11.028

Abstract
The rapid loss of eastern hemlock (Tsuga canadensis) due to infestation with hemlock woolly adelgid (Adelges tsugae, HWA) has greatly altered structure and function of eastern forests. Numerous control strategies including local pesticide use and biocontrol with predator beetles have been implemented with considerable cost and varying success. Silviculture treatments that increase incident light on surviving hemlock trees to reduce infestation and ameliorate carbon starvation have been proposed as another possible conservation strategy, yet no controlled studies have evaluated the coupled plant-insect responses to increased light. We conducted a nursery experiment on artificially infested eastern hemlock seedlings under varying levels of ambient light, ranging from 0 to 90% shade. We measured HWA infestation (ovisac density), short- and long-term indicators of carbon balance (leaf chlorophyll fluorescence, net photosynthesis, total nonstructural carbohydrate content, and shoot growth), and nutrition (leaf N content). We hypothesized that higher light would result in reduced HWA densities, higher C assimilation rates, and improved tissue non-structural carbohydrate balance; and these effects would ameliorate the effects of infestation on C balance and lead to improved seedling growth. HWA density decreased with increasing light, and was highest in the 90% shade treatments. However, photosystem II efficiency and net assimilation were also lower under the higher light treatment. Despite tradeoffs between reduced infestation and reduced leaf function from higher light, and little variation in sugar content among treatments, both leaf and root starch content and seedling growth were higher under the higher light treatment. Increasing light levels improves long-term carbon balance for hemlock seedlings in the presence of HWA. Although hemlock typically occurs in deeply shaded forests, our results suggest that silvicultural treatments such as forest thinning that increase light exposure may reduce HWA abundance and lead to better tree C balance, and may be an effective component of large-scale conservation and restoration strategies.

Bumpers PM, Rosemond AD, Maerz JC, Benstead JP. 2017. Experimental nutrient enrichment of forest streams increases energy flow to predators along greener food-web pathways. Freshw Biol. 2017;62:1794–1805. https://doi.org/10.1111/fwb.12992

Abstract
Nutrient enrichment is a key stressor of lakes and streams globally, affecting the relative availability of important basal resources such as algae and detritus. These effects are controlled by responses of autotrophic and heterotrophic microorganisms that subsequently affect primary consumers and higher level predators. Despite the potential for propagation of these bottom-up effects, few studies have examined how nutrients affect “green” (autotrophic) versus “brown” (heterotrophic) energy pathways to predators via changes in the quantity or type of prey consumed. We studied the pathways by which nutrient enrichment affected two predatory salamander species (Desmognathus quadramaculatus and Eurycea wilderae) using detailed diet analyses before and during 2-year nutrient additions to five headwater forest streams. The streams were continuously enriched with different concentrations of dissolved nitrogen (N) and phosphorus (P), creating relatively greater N or P concentrations and distinct N:P ratios (2:1, 8:1, 16:1, 32:1 and 128:1) in each stream. Nutrient addition resulted in greater prey number, size and biomass consumed by D. quadramaculatus, an effect driven more by P than by N additions. Some of these effects were greater in the second year of enrichment and were greater for larger individuals. Shifts in the prey composition of D. quadramaculatus included increases in algivores and decreases in detritivores, tracking observed treatment effects on basal resource quantity (e.g. algivore abundance in guts was related to algal biomass, which increased with enrichment, and detritivore abundance in guts was related to detrital standing stocks, which declined with enrichment). For E. wilderae diets, there was limited evidence for increased prey size and number, or for alteration of prey composition with enrichment despite evidence of increased larval growth. We hypothesise that body size differences between the two salamander species partially explain their different dietary responses to enrichment. Our results show that nutrient addition, primarily of P, affected the quantity and composition of predator diets in our nutrient-poor streams. These effects on diet were consistent with concurrent studies showing that P enrichment resulted in faster growth of salamanders and occurred partly via effects on algal biofilm or “green” food-web pathways, despite the dominance of detrital or “brown” resources in our heavily shaded forest stream sites. Thus, nutrient enrichment can promote algae- versus detritus-based energy-flow pathways in nominally light-limited stream ecosystems, with associated changes in food-web characteristics and function.

Burt, Tim & Miniat, Chelcy & H. Laseter, S & T. Swank, W. (2017). Changing patterns of daily precipitation totals at the Coweeta Hydrologic Laboratory, North Carolina, USA: COWEETA DAILY RAINFALL. International Journal of Climatology. . 10.1002/joc.5163.

Abstract
A pattern of increasing frequency and intensity of heavy rainfall over land has been documented for several temperate regions and is associated with climate change. This study examines the changing patterns of daily precipitation at the Coweeta Hydrologic Laboratory, North Carolina, USA, since 1937 for four rain gauges across a range of elevations. We analyse seasonal total rainfall, number of rain days and the frequency of heavy rainfall. We compare these with several teleconnections, including the Bermuda High Index (BHI), the West BHI, the North Atlantic Oscillation (NAO) and the El Niño-Southern Oscillation. Our data show a tendency for increased variability, including major periods of drought, with fewer rain days recently, especially in summer. Only autumn tended to have increases in rainfall frequency and magnitude; this is the season when orographic enhancement is at its strongest. The major driver of precipitation at Coweeta is the strength of the Bermuda High. The strength of the NAO is important in summer. The results are relevant to the southeast United States in general, given that the region comes under the influence of similar air masses during the year. The findings are applicable to the wider Appalachian Mountains and to other mountainous regions where there is significant orographic enhancement.

Craig, M.E. and Fraterrigo, J.M. 2017. Plant–microbial competition for nitrogen increases microbial activities and carbon loss in invaded soils. Oecologia. doi:10.1007/s00442-017-3861-0

Abstract
Many invasive plant species show high rates of nutrient acquisition relative to their competitors. Yet the mechanisms underlying this phenomenon, and its implications for ecosystem functioning, are poorly understood, particularly in nutrient-limited systems. Here, we test the hypothesis that an invasive plant species (Microstegium vimineum) enhances its rate of nitrogen (N) acquisition by outcompeting soil organic matter-degrading microbes for N, which in turn accelerates soil N and carbon (C) cycling. We estimated plant cover as an indicator of plant N acquisition rate and quantified plant tissue N, soil C and N content and transformations, and extracellular enzyme activities in invaded and uninvaded plots. Under low ambient N availability, invaded plots had 77% higher plant cover and lower tissue C:N ratios, suggesting that invasion increased rates of plant N acquisition. Concurrent with this pattern, we observed significantly higher mass-specific enzyme activities in invaded plots as well as 71% higher long-term N availability, 21% lower short-term N availability, and 16% lower particulate organic matter N. A structural equation model showed that these changes were interrelated and associated with 27% lower particulate organic matter C in invaded areas. Our findings suggest that acquisition of N by this plant species enhances microbial N demand, leading to an increased flux of N from organic to inorganic forms and a loss of soil C. We conclude that high N acquisition rates by invasive plants can drive changes in soil N cycling that are linked to effects on soil C.

Daly, C., Slater, M. E., Roberti, J. A., Laseter, S. H. and Swift, L. W. (2017), High-resolution precipitation mapping in a mountainous watershed: ground truth for evaluating uncertainty in a national precipitation dataset. Int. J. Climatol, 37: 124–137. doi:10.1002/joc.4986

Abstract
A 69-station, densely spaced rain gauge network was maintained over the period 1951–1958 in the Coweeta Hydrologic Laboratory, located in the southern Appalachians in western North Carolina, USA. This unique dataset was used to develop the first digital seasonal and annual precipitation maps for the Coweeta basin, using elevation regression functions and residual interpolation. It was found that a 10-m elevation grid filtered to an approximately 7-km effective wavelength explained the most variance in precipitation (R2 =0.82–0.95). A ‘dump zone’ of locally high precipitation a short distance downwind from the mountain crest marking the southern border of the basin was the main feature that was not explained well by the precipitation–elevation relationship. These data and maps provided a rare ‘ground-truth’ for estimating uncertainty in the national-scale Parameter-elevation Relationships on Independent SlopesModel (PRISM) precipitation grids for this location and time period. Differences between PRISM and ground-truthwere comparedwith uncertainty estimates produced by the PRISMmodel and cross-validation errors. Potential sources of uncertainty in the national PRISM grids were evaluated, including the effects of coarse grid resolution, limited station data, and imprecise station locations. The PRISM national grids matched closely (within 5%) with the Coweeta dataset. The PRISM regression prediction interval, which includes the influence of stations in an area of tens of kilometres around a given location, overestimated the local error at Coweeta (12–20%). Offsetting biases and generally low error rates made it difficult to isolate major sources of uncertainty in the PRISM grids, but station density and selection, and mislocation of stations were identified as likely sources of error. The methods used in this study can be repeated in other areas where high-density data exist to gain a more comprehensive picture of the uncertainties in national-level datasets, and can be used in network optimization exercises.

Duan, K., Sun, G., McNulty, S. G., Caldwell, P. V., Cohen, E. C., Sun, S., Aldridge, H. D., Zhou, D., Zhang, L., and Zhang, Y.: Future shift of the relative roles of precipitation and temperature in controlling annual runoff in the conterminous United States, Hydrol. Earth Syst. Sci., 21, 5517-5529, https://doi.org/10.5194/hess-21-5517-2017, 2017

Abstract
This study examines the relative roles of climatic variables in altering annual runoff in the conterminous United States (CONUS) in the 21st century, using a monthly ecohydrological model (the Water Supply Stress Index model, WaSSI) driven with historical records and future scenarios constructed from 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. The results suggest that precipitation has been the primary control of runoff variation during the latest decades, but the role of temperature will outweigh that of precipitation in most regions if future climate change follows the projections of climate models instead of the historical tendencies. Besides these two key factors, increasing air humidity is projected to partially offset the additional evaporative demand caused by warming and consequently enhance runoff. Overall, the projections from 20 climate models suggest a high degree of consistency on the increasing trends in temperature, precipitation, and humidity, which will be the major climatic driving factors accounting for 43–50, 20–24, and 16–23 % of the runoff change, respectively. Spatially, while temperature rise is recognized as the largest contributor that suppresses runoff in most areas, precipitation is expected to be the dominant factor driving runoff to increase across the Pacific coast and the southwest. The combined effects of increasing humidity and precipitation may also surpass the detrimental effects of warming and result in a hydrologically wetter future in the east. However, severe runoff depletion is more likely to occur in the central CONUS as temperature effect prevails.

Elliott, Katherine J.; Caldwell, Peter V.; Brantley, Steven T.; Miniat, Chelcy F.; Vose, James M.; Swank, Wayne T. 2017. Water yield following forest-grass-forest transitions. Hydrology and Earth System Sciences, Vol. 21(2): 17 pages.: 981-997. DOI:10.5194/hess-21-981-2017

Abstract
Many currently forested areas in the southern Appalachians were harvested in the early 1900s and cleared for agriculture or pasture, but have since been abandoned and reverted to forest (old-field succession). Land-use and land-cover changes such as these may have altered the timing and quantity of water yield (Q). We examined 80 years of streamflow and vegetation data in an experimental watershed that underwent forest–grass–forest conversion (i.e., old-field succession treatment). We hypothesized that changes in forest species composition and water use would largely explain long-term changes in Q. Aboveground biomass was comparable among watersheds before the treatment (208.3?Mgha-1), and again after 45 years of forest regeneration (217.9?Mgha-1). However, management practices in the treatment watershed altered resulting species composition compared to the reference watershed. Evapotranspiration (ET) and Q in the treatment watershed recovered to pretreatment levels after 9 years of abandonment, then Q became less (averaging 5.4% less) and ET more (averaging 4.5% more) than expected after the 10th year up to the present day. We demonstrate that the decline in Q and corresponding increase in ET could be explained by the shift in major forest species from predominantly Quercus and Carya before treatment to predominantly Liriodendron and Acer through old-field succession. The annual change in Q can be attributed to changes in seasonal Q. The greatest management effect on monthly Q occurred during the wettest (i.e., above median Q) growing-season months, when Q was significantly lower than expected. In the dormant season, monthly Q was higher than expected during the wettest months.

Evans, Sakura R., Jensen-Ryan, Danielle. 2017. Exurbanization and Its Impact on Water Resources: Stream Management among Newcomer and Generational Landowners in Southern Appalachia Appalachian Journal 44(1-2)

Abstract
Referred to as exurbanization, amenity migration, counter-urbanization, rural sprawl, or neo-rural migration, the influx of urban migrants into rural communities has been increasingly studied over the last 50 years, both domestically and internationally. Exurbanization, a term Spectorsky coined in 1955, represents a “rural restructuring” as rural communities, environments, and economies shift from agricultural, or productivist, to other post-productivist or neo-productivist landscapes. While the concept of exurbanization conforms to the general idea of “sprawl,” Cadieux explains that the characterizing feature of exurbanization that differentiates it from unplanned residential development on the urban periphery is the amount of land. She argues that exurban development is desirable specifically because it involves lowpopulation density and large parcel sizes, and it is the “material and ideological benefits of sprawling nature [that] attract amenity migrants to exurban landscapes.” Exurbanization is also the fastest growing manner of land acquisition in the United States and a primary driver of economies transitioning from natural resource extraction to the service industry. 5 Scholars have expressed growing concern over the impacts of exurbanization on environmental resources,particularly its impacts on water as increased population density applies pressure on the regional water supply due to increased water consumption. Furthermore, as residential and commercial development increase within a region to accommodate growing populations of retirees and amenity migrants, increased impervious surfaces, stream sedimentation, and erosion have resulted in impaired stream health and water quality. Yet, one of the most serious threats to stream health and water quality from exurbanization is the impact of land use decision-making at the parcel level. As more rural land becomes fragmented and sold, more landowners own smaller parcels, thus intensifying land management on regional resources. In particular, stream management by private landowners, specifically the management of riparian zones, or the area between land and rivers or streams, has been highlighted as a critical area for research and restoration. Southern Appalachia is a water-rich region with an extensive network of streams and rivers that effectively function as a water tower for the Southeastern United States. The region is also undergoing rapid exurban development, providing an excellent opportunity to determine if, and how, exurbanization is having an impact on the regional environment. When viewed as a watershed, parcel level decision-making can directly impact stream health and water quality. Therefore, we chose to examine intra-community patterns of stream management among two populations of landowners in the same community by surveying values about property and water rights, preference for stream appearance, perceptions of stream health, and stream management practices.

Ferguson, P. F.B., Conroy, M. J. and Hepinstall-Cymerman, J. (2017), Assessing conservation lands for forest birds in an exurban landscape. Jour. Wild. Mgmt., 81: 1308–1321. doi:10.1002/jwmg.21295

Abstract
Exurban development is the fastest growing type of land use in the United States and is prominent in the southern Appalachian region. A potential consequence of exurban development is the loss and fragmentation of wildlife habitat. We used a Bayesian model that accounts for false positive and false negative detections to make inferences about how the occupancy of 6 forest-dwelling, Neotropical migrant birds is related to multi-scale attributes of exurban development on land managed under 3 different conservation frameworks: national forest, land trust, or unprotected property in Macon County, North Carolina, USA during 2 breeding seasons. We performed Bayesian model selection and model averaging with a Bayesian Information Criterion weights approximation, and we evaluated models’ predictive ability. We compared results from our occupancy model to those from a traditional model assuming data had no false positives. Results indicated that landscape- and local-scale covariates were more strongly related to posterior occupancy probabilities than site-scale covariates and that landscape composition and elevation were more strongly associated with occupancy probabilities than configuration. In particular, occupancy had a positive relationship with elevation and percent forest and a negative relationship with percent development. The black-throated blue warbler (Setophaga caerulescens) and wood thrush (Hylocichla mustelina) had the lowest posterior occupancy probabilities of the focal species, suggesting that these species may need particular conservation attention. National forest sites had high occupancy, but land trust sites exhibited patterns similar to unprotected sites. Our findings can provide guidance to county land use planners and land trusts as they respond to exurban development. Also, our study demonstrates the application of an improved occupancy model that can generate more accurate inference by accounting for both types of imperfect detection while describing heterogeneity across sites and survey occasions.

Follstad Shah, J., J. Kominoski, M. Ardon, W. Dodds, M. Gessner, N. Griffiths, C. Hawkins, A. Lecerf, C. LeRoy, D. Manning, S. Johnson, A. Rosemond, R. Sinsabaugh, C. Swan, J. Webster, and L. Zeglin. (2017), Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers. Global Change Biology doi: 10.1111/gcb.13609.

Abstract
Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (Ea, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which Ea could be calculated. Higher values of Ea were correlated with lower-quality litter, but these correlations were influenced by a single, N-fixing genus (Alnus). Ea values converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the Ea was 0.34 ± 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5–21% with a 1–4 °C rise in water temperature, rather than a 10–45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in Ea values for these regions (0.75 ± 0.13 eV and 0.27 ± 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that Ea values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.

Graves, R. A., S. M. Pearson, and M. G. Turner. (2017). Landscape dynamics of floral resources affect the supply of a biodiversity-dependent cultural ecosystem service. Landscape Ecology 32:415-428.

Abstract
Context Cultural ecosystem services, many of which depend on biodiversity, are recognized as important but seldom quantified biophysically across landscapes. Furthermore, many ecosystem service models are static, and the supply of cultural ecosystem services may be misrepresented if seasonal shifts in biotic communities are ignored. Objectives We modeled landscape dynamics of wildflower blooms in a temperate montane landscape to determine (1) how floral resources (wildflower species richness, abundance, timing, and presence of charismatic species) changed over the growing season, (2) how projected wildflower viewing hotspots varied over space and time, and (3) how spatial shifts in floral resources affected potential public access to wildflower viewing. Methods Data were collected at 63 sites across a rural-to-urban gradient in the Southern Appalachian Mountains (USA). Generalized linear models were used to identify factors affecting floral resources at two temporal scales. Floral resources were projected across the landscape and hotspots of wildflower viewing were quantified using overlay analysis. Results Floral resources were affected by topoedaphic conditions, climate, and surrounding building density and changed seasonally. Seasonal models revealed locational shifts in ecosystem service hotspots, which changed the proportion of hotspots accessible to the public and identified wildflower-viewing opportunities unnoticed by static models. Conclusion Relationships between landscape gradients, biodiversity, and ecosystem service supply varied seasonally, and our models identified cultural ecosystem service hotspots otherwise obscured by simple proxies. Landscape models of biodiversity-based cultural ecosystem services should include seasonal dynamics of biotic communities to avoid under- or over-emphasizing the importance of particular locations in ecosystem service assessments.

Graves, R.A., S.M. Pearson, and M.G. Turner. 2017. Species richness alone does not predict cultural ecosystem service value. Proceedings of the National Academy of Sciences of the United States of America. (DOI:10.1073/pnas.1701370114)

Abstract
Sustaining biodiversity and ecosystem services are common conservation goals. However, understanding relationships between biodiversity and cultural ecosystem services (CES) and determining the best indicators to represent CES remain crucial challenges. We combined ecological and social data to compare CES value of wildflower communities based on observed species richness versus revealed social preferences. Using a discrete-choice experiment with images of wildflower communities, we analyzed which aspects of biodiversity were associated with the aesthetic preferences of forest visitors. Although commonly used to indicate biodiversity-based CES, species richness did not predict aesthetic preference. This study suggests that successful management of CES requires understanding stakeholders’ preferences to determine conservation priorities.

Gulis, V., K.A. Kuehn, L.N. Schoettle, D. Leach, J.P. Benstead, and A.D. Rosemond. 2017. Changes in nutrient stoichiometry, elemental homeostasis and growth rate of aquatic litter-associated fungi in response to inorganic nutrient supply. ISME Journal (Multidisciplinary Journal of Microbial Ecology) 10.1038/ismej.2017.123

Abstract
Aquatic fungi mediate important energy and nutrient transfers in freshwater ecosystems, a role potentially altered by widespread eutrophication. We studied the effects of dissolved nitrogen (N) and phosphorus (P) concentrations and ratios on fungal stoichiometry, elemental homeostasis, nutrient uptake and growth rate in two experiments that used (1) liquid media and a relatively recalcitrant carbon (C) source and (2) fungi grown on leaf litter in microcosms. Two monospecific fungal cultures and a multi-species assemblage were assessed in each experiment. Combining a radioactive tracer to estimate fungal production (C accrual) with N and P uptake measurements provided an ecologically relevant estimate of mean fungal C:N:P of 107:9:1 in litter-associated fungi, similar to the 92:9:1 obtained from liquid cultures. Aquatic fungi were found to be relatively homeostatic with respect to their C:N ratio (~11:1), but non-homeostatic with respect to C:P and N:P. Dissolved N greatly affected fungal growth rate and production, with little effect on C:nutrient stoichiometry. Conversely, dissolved P did not affect fungal growth and production but controlled biomass C:P and N:P, probably via luxury P uptake and storage. The ability of fungi to immobilize and store excess P may alter nutrient flow through aquatic food webs and affect ecosystem functioning.

Hain EF, Kennen JG, Caldwell PV, Nelson SAC, Sun G, McNulty SG. Using regional scale flow–ecology modeling to identify catchments where fish assemblages are most vulnerable to changes in water availability. Freshwater Biol. 2017;00:1–18. https://doi.org/10.1111/fwb.1304

Abstract
1. Streamflow is essential for maintaining healthy aquatic ecosystems and for supporting human water supply needs. Changes in climate, land use and water use practices may alter water availability. Understanding the potential effect of these changes on aquatic ecosystems is critical for long-term water management to maintain a balance between water for human consumption and ecosystem needs. 2. Fish species data and streamflow estimates from a rainfall-runoff and flow routing model were used to develop boosted regression tree models to predict the relationship between streamflow and fish species richness (FSR) under plausible scenarios of (1) water withdrawal, (2) climate change and (3) increases in impervious surfaces in the Piedmont ecoregion of North Carolina, U.S.A. Maximum monthly flow, the fraction of total flow originating from impervious surface runoff, coefficient of monthly streamflow variability, and the specific river basin accounted for 50% of the variability in FSR. This model was used to predict FSR values for all twelve-digit Hydrological Unit Code catchments (HUC-12s) in the North Carolina Piedmont under current flow conditions and under water withdrawal, climate change and impervious surface scenarios. 3. Flow–ecology modeling results indicate that predicted FSR declined significantly with increased water withdrawals. However, the magnitude of decline varied geographically. A “hot-spot” analysis was conducted based on predicted changes in FSR under each scenario to understand which HUC-12s were most likely to be affected by changes in water withdrawals, climate and impervious surfaces. Under the 20% withdrawal increase scenario, 413 of 886 (47%) HUC-12s in the study area were predicted to lose one or more species. HUC-12s in the Broad, Catawba, Yadkin and Cape Fear river basins were most susceptible to species loss. 4. These findings may help decision making efforts by identifying catchments most vulnerable to changing water availability. Additionally, FSR-discharge modeling results can assist resource agencies, water managers and stakeholders in assessing the effect of water withdrawals in catchments to better support the protection and long-term conservation of species.

Hawthorne S, Miniat CF. Topography may mitigate drought effects on vegetation along a hillslope gradient. Ecohydrology. 2017;e1825. https://doi.org/10.1002/eco.1825

Abstract
Topography may mitigate drought effects on vegetation along a hillslope gradient through redistribution of soil moisture. We examined the interaction of topography, climate, soil moisture, and transpiration in a low-elevation, mixed-hardwood forest in the southern Appalachian Mountains. The effects of meteorological variation (wet and dry years) and topographic position (upslope and cove) were tested on daily soil moisture amplitude and recession and plot and species-specific transpiration. Trees in the cove plot were 17% taller and had 45% greater sapwood area than those in the upslope plot. Lower rates of soil moisture recession following rainfall events were observed at the cove plot compared to the upper plot. Greater daily soil moisture amplitude and plot transpiration, even in dry years, suggest that lower slope positions may have been buffered against moderate drought. We also observed similar transpiration in Quercus spp., Carya spp., and Liriodendron tulipifera in the cove plot between dry and wet years. Plot transpiration was reduced by 51% in the dry year in the upslope plot only, and transpiration by individual species in the plot reflected this pattern, suggesting water stress in dry years may be exacerbated by topography. With drought predicted to increase for these systems, the different drought responses of species, in addition to topographic effects, may lead to complex shifts in species composition.

Jackson CR, Webster JR, Knoepp JD, et al. Unexpected ecological advances made possible by long-term data: A Coweeta example. WIREs Water. 2018;e1273. https://doi.org/10.1002/wat2.1273

Abstract
In the 1970s, Forest Service and academic researchers clearcut the forest in Watershed 7 in the Coweeta Basin to observe how far the perturbation would move the ecosystem and how quickly the ecosystem would return to its predisturbance state. Our long-term observations demonstrated that this view of resistance and resilience was too simplistic. Forest disturbance triggered a chain of ecological dynamics that are still evolving after 40?years. Short-term pulses in dissolved inorganic nitrogen (DIN) (3?years) and streamflows (4?years) were followed by several years in which the system appeared to be returning to predisturbance conditions. Then however, changes in forest composition triggered a regime change in DIN dynamics from biological to hydrological control as well as persistent high stream DIN levels mediated by climatic conditions. These forest composition changes also led to later reductions in streamflow. These long-term observations of streamflows, stream DIN concentrations, stream DIN exports, and stand composition have substantially advanced our understanding of forest ecosystem dynamics; and they demonstrate the value of long-term observational data in revealing ecosystem complexities and surprises, generating new hypotheses, and motivating mechanistic research. Shorter observational records from this experiment would have produced incomplete or erroneous inference.

Jackson, C. Rhett, Robert A. Bahn, and Jackson R. Webster, 2017. Water Quality Signals from Rural Land Use and Exurbanization in a Mountain Landscape: What’s Clear and What’s Confounded? Journal of the American Water Resources Association (JAWRA) 53(5):1212-1228. https://doi.org/10.1111/1752-1688.12567

Abstract
The overall influence of urbanization on how flows of different frequency might change over time, while important in hydrologic design, remains imprecisely known. In this study, we investigate the effects of urbanization on flow duration curves (FDCs) and flow variability through a case study of eight watersheds that underwent different amounts of growth, in the Puget Sound region in Western Washington State, United States. We computed annual FDCs from flow records spanning 1960-2010 and, after accounting for the effects of precipitation, we conducted statistical trend analyses on flow metrics to quantify how key FDC percentiles changed with time in response to urbanization. In the urban watersheds, the entire FDC tended to increase in magnitude of flow, especially the 95th-99th percentile of the daily mean flow series, which increased by an average of 43%. Stream flashiness in urban watersheds was found to increase by an average of 70%. The increases in FDC magnitude and flashiness in urbanizing watersheds are most likely a result of increasing watershed imperviousness and altered hydrologic routing. Rural watersheds were found to have decreasing FDC magnitude over the same time period, which is possibly due to anthropogenic extractions of groundwater, and increasing stream flashiness, which is likely a result of reductions in base flow and increasing precipitation intensity and variability.

Keiser, A.D., M.A. Bradford (2017),Climate masks decomposer influence in a cross-site litter decomposition study, Soil Biology and Biochemistry, 107 , pp. 180–187, 10.1016/j.soilbio.2016.12.022

Abstract
Leaf litter is a significant input of carbon and nutrients to forested systems. Rates of foliar decomposition, and cycling of carbon and nutrients, appear consistently explained by climate and litter quality. Although the soil decomposer community actually mineralizes litter, its independent role is often undetected in cross-site studies. At three sites along an elevational gradient in eastern U.S. temperate forest, we used a reciprocal litter transplant design to explore whether climate masks the functional influence of the decomposer community on litter decomposition dynamics in the short- and longer-term. Climate, measured as the climate decomposition index, best predicted mass loss in the longer term, over 23 and 31 months (the maximum incubation period). However, decomposer community function also predicted mass loss dynamics across the same time period. Therefore, climate effects on mass loss correlated positively with differences in the functional ability of the three soil decomposer communities. Our findings suggest that climate ‘masks’ the independent influence of the soil decomposer community over litter mass loss dynamics, because direct positive effects of more favorable climate on decomposition rates appear correlated with greater functional potential of the decomposer communities. These results fit within existing theory and experimental evidence that soil microorganisms both adapt to their climate regime, and are directly, through biotic activity, and indirectly, via community structure or function, affected by climate. These non-linear effects of climate may then amplify decomposer function in warm environments and suppress function in cool environments. Hence, our results suggest that decomposition relationships observed across spatial gradients may fail to adequately represent how decomposition will respond to changing climate across time.

Kominoski, J. S., Rosemond, A. D., Benstead, J. P., Gulis, V. and Manning, D. W. P. (2017), Experimental nitrogen and phosphorus additions increase rates of stream ecosystem respiration and carbon loss. Limnol. Oceanogr.. doi:10.1002/lno.10610

Abstract
Nitrogen (N) and phosphorus (P) enrichment reduces organic carbon (C) storage in detritus-based stream ecosystems, but the relative effects of N and P concentrations and ratios on stream metabolic rates have not previously been tested. We tracked changes in whole-stream ecosystem respiration (ER) and gross primary productivity (GPP), particulate organic matter (POM) standing stocks, fungal biomass, and POM-specific respiration rates before and during 2 yr of experimental N and P enrichment in five forest streams. Nutrient additions (~ 96 µg N L-1 to ~ 472 µg N L-1 and ~ 10 µg P L-1 to ~ 85 µg P L-1) targeted dissolved N : P molar ratios of 2, 8, 16, 32, and 128. Whole-stream ER was positively related to standing stock of wood, a seasonably stable POM compartment that varied by up to 2× among streams. Nutrient enrichment generally increased ER but had no effect on low-level GPP. Prior to nutrient enrichment, ER was higher at lower N : P, but during enrichment ER increased with increasing N : P. Respiration rates on leaf litter and wood increased with enrichment but decreased with increasing P, and the quantity of leaf litter generally declined with increasing N. Respiration rates on fine benthic organic matter (FBOM) were higher with increasing N : P, and FBOM standing stocks decreased with increasing N. Fungal biomass did not change with nutrient enrichment. Compared to pre-enrichment conditions, nutrients increased seasonal variation in leaf litter standing stocks and whole-stream respiration rates. Our results demonstrate how nutrient-stimulated loss of C from detritus-based ecosystems occurs through the maintenance of enhanced respiration rates on detrital resources that are particularly sensitive to N inputs.

L. Lin, J.S. Norman, J.E. Barrett. 2017. Ammonia-uptake kinetics and domain-level contributions of bacteria and archaea to nitrification in temperate forest soils. Ecological Modelling 362:111-119. DOI:10.1016/j.ecolmodel.2017.08.016

Abstract
Ammonia-oxidizing bacteria and archaea (AOA and AOB) perform the rate-limiting step of nitrification, a biogeochemical process that controls the availability of inorganic nitrogen in terrestrial and aquatic ecosystems. We sought to investigate field values of AOA and AOB ammonia-uptake kinetics along with domain-level contributions to ammonia oxidation in temperate forest soils. To accomplish this goal, we constructed an ecosystem model that simulates ammonia oxidation in temperate forest soils based only on inorganic nitrogen pools and AOA and AOB population dynamics observed during in situ incubations. The model used Bayesian Markov chain Monte Carlo procedure to choose the most likely combination of in situ ammonia-uptake parameters for AOA and AOB, including Km,AOA, Km,AOB, Vmax,AOA, and Vmax,AOB. Domain-level contributions to ammonia oxidation were extracted from the best-fit solution and the model-selected values indicate that AOB was responsible for 70.0% of the simulated ammonia oxidation across sites, while AOA was responsible for the remaining 30.0%. We believe that the approach we demonstrate here can be applied to microbially-mediated biogeochemical fluxes in other elemental cycles as well.

Leigh, David S. 2017. Vertical accretion sand proxies of gaged floods along the upper Little Tennessee River, Blue Ridge Mountains, USA. Sedimentary Geology. DOI:10.1016/j.sedgeo.2017.09.007.

Abstract
Understanding environmental hazards presented by river flooding has been enhanced by paleoflood analysis, which uses sedimentary records to document floods beyond historical records. Bottomland overbank deposits (e.g., natural levees, floodbasins, meander scars, low terraces) have the potential as continuous paleoflood archives of flood frequency and magnitude, but they have been under-utilized because of uncertainty about their ability to derive flood magnitude estimates. The purpose of this paper is to provide a case study that illuminates tremendous potential of bottomland overbank sediments as reliable proxies of both flood frequency and magnitude. Methods involve correlation of particle-size measurements of the coarse tail of overbank deposits (> 0.25 mm sand) from three separate sites with historical flood discharge records for the upper Little Tennessee River in the Blue Ridge Mountains of the southeastern United States. Results show that essentially all floods larger than a 20% probability event can be detected by the coarse tail of particle-size distributions, especially if the temporal resolution of sampling is annual or sub-annual. Coarser temporal resolution (1.0 to 2.5 year sample intervals) provides an adequate record of large floods, but is unable to discriminate individual floods separated by only one to three years. Measurements of > 0.25 mm sand that are normalized against a smoothed trend line through the down-column data produce highly significant correlations (R2 values of 0.50 to 0.60 with p-values of 0.004 to < 0.001) between sand peak values and flood peak discharges, indicating that flood magnitude can be reliably estimated. In summary, bottomland overbank deposits can provide excellent continuous records of paleofloods when the following conditions are met: 1) Stable depositional sites should be chosen; 2) Analysis should concentrate on the coarse tails of particle-size distributions; 3) Sampling of sediment intervals should achieve annual or better resolution; 4) Time-series data of particle-size should be detrended to minimize variation from dynamic aspects of fluvial sedimentation that are not related to flood magnitude; and 5) Multiple sites should be chosen to allow for replication of findings.

Manning DWP, Rosemond AD, Gulis V, Benstead JP, Kominoski JS. (2017), Nutrients and temperature additively increase stream microbial respiration. Glob Change Biol.;00:1–15. https://doi.org/10.1111/gcb.13906

Abstract
Rising temperatures and nutrient enrichment are co-occurring global-change drivers that stimulate microbial respiration of detrital carbon, but nutrient effects on the temperature dependence of respiration in aquatic ecosystems remain uncertain. We measured respiration rates associated with leaf litter, wood, and fine benthic organic matter (FBOM) across seasonal temperature gradients before (PRE) and after (ENR1, ENR2) experimental nutrient (nitrogen [N] and phosphorus [P]) additions to five forest streams. Nitrogen and phosphorus were added at different N:P ratios using increasing concentrations of N (~80–650 µg/L) and corresponding decreasing concentrations of P (~90–11 µg/L). We assessed the temperature dependence, and microbial (i.e., fungal) drivers of detrital mass-specific respiration rates using the metabolic theory of ecology, before vs. after nutrient enrichment, and across N and P concentrations. Detrital mass-specific respiration rates increased with temperature, exhibiting comparable activation energies (E, electronvolts [eV]) for all substrates (FBOM E = 0.43 [95% CI = 0.18–0.69] eV, leaf litter E = 0.30 [95% CI = 0.072–0.54] eV, wood E = 0.41 [95% CI = 0.18–0.64] eV) close to predicted MTE values. There was evidence that temperature-driven increased respiration occurred via increased fungal biomass (wood) or increased fungal biomass-specific respiration (leaf litter). Respiration rates increased under nutrient-enriched conditions on leaves (1.32×) and wood (1.38×), but not FBOM. Respiration rates responded weakly to gradients in N or P concentrations, except for positive effects of P on wood respiration. The temperature dependence of respiration was comparable among years and across N or P concentration for all substrates. Responses of leaf litter and wood respiration to temperature and the combined effects of N and P were similar in magnitude. Our data suggest that the temperature dependence of stream microbial respiration is unchanged by nutrient enrichment, and that increased temperature and N + P availability have additive and comparable effects on microbial respiration rates.

Martin KL, Hwang T, Vose JM, et al. (2017) Watershed impacts of climate and land use changes depend on magnitude and land use context. Ecohydrology.;e1870. https://doi.org/10.1002/eco.1870

Abstract
Human population growth and urban development are affecting climate, land use, and the ecosystem services provided to society, including the supply of freshwater. We investigated the effects of land use and climate change on water resources in the Yadkin–Pee Dee River Basin of North Carolina, United States. Current and projected land uses were modeled at high resolution for three watersheds representing a forested to urban land use gradient by melding the National Land Cover Dataset with data from the U.S. Forest Service Forest Inventory and Analysis. Forecasts for 2051–2060 of regional land use and climate for scenarios of low (B2) and moderately high (A1B) rates of change, coupled with multiple global circulation models (MIROC, CSIRO, and Hadley), were used to inform a distributed ecohydrological model. Our results identified increases in water yields across the study watersheds, primarily due to forecasts of increased precipitation. Climate change was a more dominant factor for future water yield relative to land use change across all land uses (forested, urban, and mixed). When land use change was high (27% of forested land use was converted to urban development), it amplified the impacts of climate change on both the magnitude and timing of water yield. Our fine-scale (30-m) distributed combined modeling approach of land use and climate change identified changes in watershed hydrology at scales relevant for management, emphasizing the need for modeling efforts that integrate the effects of biophysical (climate) and social economic (land use) changes on the projection of future water resource scenarios.

Meyers, B.J.E., C.A., Dolloff, J.R. Webster, K.H. Nislow, B. Fair, and A.L. Rypel. (2017), Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient. Ecology of Freshwater Fish, DOI: 10.1111/eff.12352.

Abstract
Production of biomass is central to the ecology and sustainability of fish assemblages. The goal of this study was to empirically estimate and compare fish assemblage production, production-to-biomass (P/B) ratios and species composition for 25 second to third-order streams spanning the Appalachian Mountains (from Vermont to North Carolina) that vary in their temperature regimes. Fish assemblage production estimates ranged from 0.15 to 6.79g m-2 year-1, and P/B ratios ranged from 0.20 to 1.07. There were no significant differences in mean assemblage production across northern cold-water, southern cold-water and southern cool-water streams (p = .35). Two warm-water streams, not included in these comparisons, had the highest mean production and biomass values. Mean assemblage P/B was significantly higher in northern cold-water streams relative to southern cold-water and cool-water streams (p = .01). Species evenness in production declined with stream temperature and differed significantly across the lower latitude cold-water, cool-water and warm-water streams and the higher latitude (i.e. more northern) cold-water streams. Our fish assemblage production estimates and P/B ratios were both lower and higher compared to previously published estimates for similar stream habitats. This study provides empirical fish assemblage production estimates to inform future research on southern Appalachian streams and on the potential impacts of varying temperature regimes on cold- water, cool-water and warm-water fish production in the coming decades as climate change continues to threaten fish assemblages.

Minucci, J. M., Miniat, C. F., Teskey, R. O. and Wurzburger, N. (2017), Tolerance or avoidance: drought frequency determines the response of an N2-fixing tree. New Phytol, 215: 434–442. doi:10.1111/nph.14558

Abstract
 Climate change is increasing drought frequency, which may affect symbiotic N2 fixation (SNF), a process that facilitates ecosystem recovery from disturbance. Here, we assessed the effect of drought frequency on the ecophysiology and SNF rate of a common N2-fixing tree in eastern US forests.  We grew Robinia pseudoacacia seedlings under the same mean soil moisture, but with different drought frequency caused by wet–dry cycles of varying periodicity.  We found no effect of drought frequency on final biomass or mean SNF rate. However, seedlings responded differently to wet and dry phases depending on drought frequency. Under low-frequency droughts, plants fixed carbon (C) and nitrogen (N) at similar rates during wet and dry phases. Conversely, under high-frequency droughts, plants fixed C and N at low rates during dry phases and at high rates during wet phases.  Our findings suggest that R. pseudoacacia growth is resistant to increased drought frequency because it employs two strategies – drought tolerance or drought avoidance, followed by compensation. SNF may play a role in both by supplying N to leaf tissues for acclimation and by facilitating compensatory growth following drought. Our findings point to SNF as a mechanism for plants and ecosystems to cope with drought.

Northington, R.M. and Webster, J.R. 2017. Experimental reductions in stream flow alter litter processing and consumer subsidies in headwater streams. Freshw Biology. 62: 737–750. (DOI:10.1111/fwb.12898)

Abstract
Forested headwater streams are connected to their surrounding catchments by a reliance on terrestrial subsidies. Changes in precipitation patterns and stream flow represent a potential disruption in stream ecosystem function, as the delivery of terrestrial detritus to aquatic consumers and downstream transport are compromised. The potential effect of drying on decomposition is critical to understanding ecosystem processes in these detritus-driven ecosystems. In this study, we experimentally altered stream connectivity to examine how altered water availability would influence litter decomposition. We used three catchments in the Coweeta Hydrologic Lab in North Carolina, U.S.A., establishing sites that were always wet, intermediately wet and completely terrestrial, while also experimentally diverting significant surface flow from downstream locations for several months. The flow manipulation significantly reduced the amount of water available to the three study reaches, leading to drastic changes in organic matter accumulation. Stream temperature and dissolved oxygen changed during the manipulation but only in response to season. Nutrient concentrations remained low or below detection during the experiment, demonstrating no response to the manipulation. Red maple and white oak demonstrated significantly different mass loss during the first few days of the experiment, but by the completion of the experiment, location was a more significant determinant of breakdown rate than leaf identity. Leaves placed in sites that were consistently wet decomposed at a higher rate than those in bank or terrestrial sites. Initially, leaf decomposition varied significantly based on site type and presence of water, which led to disruptions in microbial and macroinvertebrate colonisation and processing. High flows during large winter storms reconnected dried reaches and stimulated rates of decomposition due to colonisation by microbes and macroinvertebrates. Macroinvertebrate densities tracked microbial biomass accumulation on leaves, but were dependent upon location. Leaves in the manipulated reaches had significantly higher macroinvertebrate densities compared to the upstream control in the winter and spring in response to the delayed wetting of large standing stocks of leaves and subsequent colonisation by microbes. Our study demonstrated that even minor disruptions in stream connectivity at key times of the year have community- and ecosystem-level influences that alter decomposition. The resilience of these ecosystems will depend on the frequency of disturbances and the ability of organisms to adapt to changing resource conditions.

Rose, K. C., R. A. Graves, W. D. Hansen, B. J. Harvey, J. Qiu, S. A. Wood, C. Ziter, and M. G. Turner. 2017. Historical foundations and future directions in macrosystems ecology. Ecology Letters 20:147-157

Abstract
Macrosystems ecology is an effort to understand ecological processes and interactions at the broadest spatial scales and has potential to help solve globally important social and ecological challenges. It is important to understand the intellectual legacies underpinning macrosystems ecology: How the subdiscipline fits within, builds upon, differs from and extends previous theories. We trace the rise of macrosystems ecology with respect to preceding theories and present a new hypothesis that integrates the multiple components of macrosystems theory. The spatio-temporal anthropogenic rescaling (STAR) hypothesis suggests that human activities are altering the scales of ecological processes, resulting in interactions at novel space–time scale combinations that are diverse and predictable. We articulate four predictions about how human actions are “expanding”, “shrinking”, “speeding up” and “slowing down” ecological processes and interactions, and thereby generating new scaling relationships for ecological patterns and processes. We provide examples of these rescaling processes and describe ecological consequences across terrestrial, freshwater and marine ecosystems. Rescaling depends in part on characteristics including connectivity, stability and heterogeneity. Our STAR hypothesis challenges traditional assumptions about how the spatial and temporal scales of processes and interactions operate in different types of ecosystems and provides a lens through which to understand macrosystem-scale environmental change.

Scaife, C. I., and L. E. Band (2017), Nonstationarity in threshold response of stormflow in southern Appalachian headwater catchments, Water Resour. Res., 53, 6579–6596, doi:10.1002/2017WR020376.

Abstract
Threshold behavior of stormflow response is an emergent pattern observed in several studies demonstrating subsurface storage controls on catchment rainfall-runoff dynamics. These studies demonstrate a distinct transition from negligible stormflow discharge response to rapid, linearly increasing stormflow identified by a single, uniquely defined threshold as a basic catchment attribute that relates to geophysical properties. Utilizing precipitation, streamflow, and soil moisture data spanning 15 years from three catchments at the Coweeta Hydrologic Laboratory (CHL), we analyze how threshold behavior forms and varies at several timescales. We pose three hypotheses: (1) stormflow thresholds form at CHL as a function of antecedent soil moisture and gross precipitation, (2) thresholds vary seasonally and interannually, and (3) threshold variation through time implies greater long-term complexity of runoff controls beyond catchment geophysical properties, including forest canopy ecohydrologic feedbacks. We isolate threshold behavior of stormflow using piecewise regression analysis in short to long-term data sets with respect to antecedent soil moisture index and gross precipitation. We use this to investigate threshold variation over seasonal, interannual, and decadal timescales that encompass hydroclimatic extremes. Seasonal analysis reveals that thresholds are more variable between growing seasons than between dormant seasons. In growing seasons with greater water stress, stormflow thresholds are lower after controlling for soil moisture storage suggesting more complex, long-term rainfall-runoff relationships as a result of forest canopy response to water stress. We present a conceptual model of how vegetation-climate nteractions influence long-term rainfall- runoff relationships creating interannual variability of stormflow thresholds and linear stormflow response.

Sourdril A., Welch-Devine M., Andrieu É, Bélaïdi N., 2017. Do April showers bring May flowers? Knowledge and perceptions of local biodiversity influencing understanding of global environmental change. A presentation of the PIAF project. Nat. Sci. Soc. Vol, No, 1–7.

Abstract
The multidisciplinary and comparative PIAF program (ANR Jeunes Chercheurs 2014-2018) uses perceptions and discourse relating to biodiversity to investigate local understandings of environmental change and strategies for adaptation to those changes. Beginning from the hypothesis that a person's connection to the environment differs according to his or her degree of dependence on natural resources and place of residence, we examine perceptions and strategies on an urban-rural-protected area gradient in four northern and southern countries (France, the United States, Cameroon, and Zimbabwe). PIAF brings together social and natural scientists who seek to contribute to our understanding of perceptions and knowledge related to environmental change and, more globally, to our understanding of social-ecological interactions in a situation of change, social and environmental tensions, and dynamics of socio-ecological systems.

Stoker, D., A. J. Falkner, K. M. Murray, A. K. Lang, T. R. Barnum, J. Hepinstall-Cymerman, M. J. Conroy, R. J. Cooper, and C. M. Pringle. (2017). Decomposition of terrestrial resource subsidies in headwater streams: Does consumer diversity matter? Ecosphere 8(6):e01868. 10.1002/ecs2.1868

Abstract
Resource subsidies and biodiversity are essential for maintaining community structure and ecosystem functioning, but the relative importance of consumer diversity and resource characteristics to decomposition remains unclear. Forested headwater streams are detritus-based systems, dependent on leaf litter inputs from adjacent riparian ecosystems, and decomposition of these resources is an important ecosystem function. Here, we examined the effects of consumer community diversity on leaf decomposition in a reciprocal transplant experiment. We asked (1) whether stream consumer communities are adapted to local resources and (2) how functional trait diversity among communities affects the leaf decomposition process. We did not find evidence that communities were adapted to locally derived resource subsidies. Instead, we found that consumer biomass and functional trait diversity as well as resource characteristics were the primary biotic drivers of decomposition. Consumer biomass was stimulated by specific resource subsidies, leading to direct and indirect effects of resource subsidies on ecosystem functioning. Contrary to current theory, we show that decomposition was higher with decreased detritivore functional diversity, suggesting dominant traits encompassing a specific niche increased decomposition. We also show that top-down, consumer diversity effects can be equal in magnitude to the bottom-up effects of resource characteristics during the decomposition process. Our research illustrates the importance of considering multiple biotic and abiotic drivers interacting via multiple pathways to affect a crucial ecosystem function.

Tor-ngern, P., Oren, R., Oishi, A. C., Uebelherr, J. M., Palmroth, S., Tarvainen, L., Ottosson-Löfvenius, M., Linder, S., Domec, J.-C. and Näsholm, T. (2017), Ecophysiological variation of transpiration of pine forests: synthesis of new and published results. Ecol Appl, 27: 118–133. doi:10.1002/eap.1423

Abstract
Canopy transpiration (EC) is a large fraction of evapotranspiration, integrating physical and biological processes within the energy, water, and carbon cycles of forests. Quantifying EC is of both scientific and practical importance, providing information relevant to questions ranging from energy partitioning to ecosystem services, such as primary productivity and water yield. We estimated EC of four pine stands differing in age and growing on sandy soils. The stands consisted of two wide-ranging conifer species: Pinus taeda and Pinus sylvestris, in temperate and boreal zones, respectively. Combining results from these and published studies on all soil types, we derived an approach to estimate daily EC of pine forests, representing a wide range of conditions from 35° S to 64° N latitude. During the growing season and under moist soils, maximum daily EC (ECm) at day-length normalized vapor pressure deficit of 1 kPa (ECm-ref) increased by 0.55 ± 0.02 (mean ± SE) mm/d for each unit increase of leaf area index (L) up to L = ~5, showing no sign of saturation within this range of quickly rising mutual shading. The initial rise of ECm with atmospheric demand was linearly related to ECm-ref. Both relations were unaffected by soil type. Consistent with theoretical prediction, daily EC was sensitive to decreasing soil moisture at an earlier point of relative extractable water in loamy than sandy soils. Our finding facilitates the estimation of daily EC of wide-ranging pine forests using remotely sensed L and meteorological data. We advocate an assembly of worldwide sap flux database for further evaluation of this approach.

Veach, A.M., Stokes, C.E., Knoepp, J. et al. (2017). Fungal Communities and Functional Guilds Shift Along an Elevational Gradient in the Southern Appalachian Mountains, Microb Ecol 10.1007/s00248-017-1116-6

Abstract
Nitrogen deposition alters forest ecosystems particularly in high elevation, montane habitats where nitrogen deposition is greatest and continues to increase. We collected soils across an elevational (788–1940 m) gradient, encompassing both abiotic (soil chemistry) and biotic (vegetation community) gradients, at eight locations in the southern Appalachian Mountains of southwestern North Carolina and eastern Tennessee. We measured soil chemistry (total N, C, extractable PO4, soil pH, cation exchange capacity [ECEC], percent base saturation [% BS]) and dissected soil fungal communities using ITS2 metabarcode Illumina MiSeq sequencing. Total soil N, C, PO4, % BS, and pH increased with elevation and plateaued at approximately 1400 m, whereas ECEC linearly increased and C/N decreased with elevation. Fungal communities differed among locations and were correlated with all chemical variables, except PO4, whereas OTU richness increased with total N. Several ecological guilds (i.e., ectomycorrhizae, saprotrophs, plant pathogens) differed in abundance among locations; specifically, saprotroph abundance, primarily attributable to genus Mortierella, was positively correlated with elevation. Ectomycorrhizae declined with total N and soil pH and increased with total C and PO4 where plant pathogens increased with total N and decreased with total C. Our results demonstrate significant turnover in taxonomic and functional fungal groups across elevational gradients which facilitate future predictions on forest ecosystem change in the southern Appalachians as nitrogen deposition rates increase and regional temperature and precipitation regimes shift.

Warren, R.J., Love, J.P. & Bradford, M.A. (2017), Nest-mediated seed dispersal, Plant Ecol 218: 1213. https://doi.org/10.1007/s11258-017-0763-5

Abstract
Many plant seeds travel on the wind and through animal ingestion or adhesion; however, an overlooked dispersal mode may lurk within those dispersal modes. Viable seeds may remain attached or embedded within materials birds gather for nest building. Our objective was to determine if birds inadvertently transport seeds when they forage for plant materials to build, insulate, and line nests. We also hypothesized that nest-mediated dispersal might be particularly useful for plants that use mating systems with self-fertilized seeds embedded in their stems. We gathered bird nests in temperate forests and fields in eastern North America and germinated the plant material. We also employed experimental nest boxes and performed nest dissections to rule out airborne and fecal contamination. We found that birds collect plant stem material and mud for nest construction and inadvertently transport the seeds contained within. Experimental nest boxes indicated that bird nests were not passive recipients of seeds (e.g., carried on wind), but arrived in the materials used to construct nests. We germinated 144 plant species from the nests of 23 bird species. A large proportion of the nest germinants were graminoids containing self-fertilized seeds inside stems—suggesting that nest dispersal may be an adaptive benefit of closed mating systems. Avian nest building appears as a dispersal pathway for hundreds of plant species, including many non-native species, at distances of at least 100–200 m. Wepropose a newplant dispersal guild to describe this phenomenon, caliochory (calio = Greek for nest).

Wurzburger, N. and Brookshire, E. N. J. (2017), Experimental evidence that mycorrhizal nitrogen strategies affect soil carbon. Ecology, 98: 1491–1497. doi:10.1002/ecy.1827

Abstract
Most land plants acquire nitrogen (N) through associations with arbuscular (AM) and ectomycorrhizal (ECM) fungi, but these symbionts employ contrasting strategies for N acquisition, which may lead to different stocks of soil carbon (C). We experimentally test this hypothesis with a mesocosm system where AM and ECM tree seedling roots, or their hyphae only, could access mineral soils with 13C- and 15N-enriched organic matter. We quantified loss of soil C and N, plant uptake of N and new inputs of plant C to soil. We found that AM, but not ECM, seedlings reduced soil C relative to controls. Soil C loss was greater in the presence of roots relative to hyphae only for both AM and ECM seedlings, but was correlated with plant N uptake for AM seedlings only. While new plant C inputs stimulated soil C loss in both symbioses, we detected plant C inputs more frequently and measured higher rates of decomposer activity in soils colonized by AM relative to ECM seedlings. Our study experimentally demonstrates how mycorrhizal strategies for N can affect soil C and C:N, even at the scale of an individual plant. Such effects may contribute to broad patterns in soil C across terrestrial ecosystems.

Ziter, C., Graves, R.A. & Turner, M.G. (2017), How do land-use legacies affect ecosystem services in United States cultural landscapes?, Landscape Ecol . doi:10.1007/s10980-017-0545-4

Abstract
Context Landscape-scale studies of ecosystem services (ES) have increased, but few consider land-use history. Historical land use may be especially important in cultural landscapes, producing legacies that influence ecosystem structure, function, and biota that in turn affect ES supply. Objectives Our goal was to generate a conceptual framework for understanding when land-use legacies matter for ES supply in well-studied agricultural, urban, and exurban US landscapes.Methods We synthesized illustrative examples from published literature in which landscape legacies were demonstrated or are likely to influence ES. Results We suggest three related conditions in which land-use legacies are important for understanding current ES supply. (1) Intrinsically slow ecological processes govern ES supply, illustrated for soil-based and hydrologic services impaired by slowly processed pollutants. (2) Time lags between land-use change and ecosystem responses delay effects on ES supply, illustrated for biodiversity-based services that may experience an ES debt. (3) Threshold relationships exist, such that changes in ES are difficult to reverse, and legacy lock-in disconnects contemporary landscapes from ES supply, illustrated by hydrologic services. Mismatches between contemporary landscape patterns and mechanisms underpinning ES supply yield unexpected patterns of ES. Conclusions Today’s land-use decisions will generate tomorrow’s legacies, and ES will be affected if processes underpinning ES are affected by land-use legacies. Research priorities include understanding effects of urban abandonment, new contaminants, and interactions of land-use legacies and climate change. Improved understanding of historical effects will improve management of contemporary ES, and aid in decision-making as new challenges to sustaining cultural landscapes arise.

Allen, Karen E. and Rebecca Moore. 2016. Moving beyond the exchange value in the nonmarket valuation of ecosystem services. Ecosystem Services 18:78-86. doi:10.1016/j.ecoser.2016.02.002.

Abstract
There has been much discussion across the ecosystem services literature as to the role of economic valuation in identifying ecosystem service values and shaping policy. This article demonstrates a non-typical use of a nonmarket valuation technique known as the stated choice experiment (CE) for understanding a range of public preferences for stream-related ecosystem services in Macon County, NC. The experiment was carried out as part of the National Science Foundation funded Coweeta Long Term Ecological Research initiative, and it reflects an interdisciplinary attempt to produce knowledge regarding ecosystem service values that is of relevance to policy makers. The CE uses a split-sample design to test for the impact of mechanism of program implementation on respondent preferences and demonstrate a range of public willingness to pay (WTP) for stream health improvements. Responses are analyzed with a latent class logit and the results show that altering the mechanism of program implementation changes the latent class composition. Results also demonstrate consistent preferences for certain attributes of stream health, but WTP for ecosystem service provisioning varies widely with proposed program implementation. The use of the CE in this research demonstrates the flexibility of the tool for combining with interdisciplinary knowledge, as well as the usefulness of information provided by nonmarket valuation techniques for informing policy design.

Bell, D.M. & Clark, J.S. (2016), Seed predation and climate impacts on reproductive variation in temperate forests of the southeastern USA, Oecologia 180: 1223. doi:10.1007/s00442-015-3537-6

Abstract
Climatic effects on tree recruitment will be determined by the interactive effects of fecundity and seed predation. Evaluating how insect and vertebrate seed predators mediate tree reproductive responses to climate depends on long-term studies of seed production, development, and predation. In this study, our objectives were to (1) assess the effects of interannual climate variation on seed abortion rates, (2) assess the impact of seed density on predation rates, and (3) examine the degree to which density-dependent seed predation would amplify or dampen interannual variation in fecundity associated with seed abortion. We used a 19-year study of seed abortion and pre-dispersal predation rates by insects and vertebrates (birds and rodents) for five temperate tree species across forest plots from the North Carolina Piedmont to the Southern Appalachian Mountains in the southeastern USA. We found that rates of seed abortion and predation increased reproductive variation for oaks (Quercus species). Probability of seed abortion was greatest during years with cool, dry springs. Responses of seed predation on Quercus species to current year’s seed density varied by species, but exhibited positive density-dependence to previous year’s seed density consistent with numerical responses of seed predators. Seed abortion and predation rates for two drupe species responded little to variation in climate or seed density, respectively. Given that predation increased interannual variation in seed availability and the negative density-dependence to previous year’s seed density, our results indicate that consistent numerical responses of oak seed predators may amplify interannual variation due to climate-mediated processes like seed abortion.

Berdanier, A. and J.S. Clark. 2016. Multi-year drought-induced morbidity preceding tree death in Southeastern US forests. Ecological Applications 26(1):17-23. doi: 10.1890/15-0274.1

Abstract
Recent forest diebacks combined with threats of future drought focus attention on the extent to which tree death is caused by catastrophic events as opposed to chronic declines in health that accumulate over years. While recent attention has focused on large-scale diebacks, there is concern that increasing drought stress and chronic morbidity may have pervasive impacts on forest composition in many regions. Here we use long-term, whole-stand inventory data from Southeastern US forests to show that trees exposed to drought experience multi-year declines in growth prior to mortality. Following a severe, multi-year drought, 72% of trees that did not recover their pre-drought growth rates died within 10 years. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with drought tolerance. These findings support the ability of trees to avoid death during drought events but indicate shifts that could occur over decades. Tree mortality following drought is predictable in these ecosystems based on growth declines, highlighting an opportunity to address multi-year drought-induced morbidity in models, experiments, and management decisions

Berdanier, A. B., and J. S. Clark. 2016. Divergent reproductive allocation trade-offs with canopy exposure across tree species in temperate forests. Ecosphere 7(6):e01313. 10.1002/ecs2.1313

Abstract
Variation in tree reproduction can alter forest community dynamics, especially if reproductive output is costly for other functions like growth. However, empirical studies reach con?icting conclusions about the constraints on reproductive allocation relative to growth and how they vary through time, across species, and between environments. Here, we test the hypothesis that a critical resource, canopy exposure to light availability, limits reproductive allocation by comparing long-term relationships between reproduction and growth for trees from 21 species in forests throughout the Southeastern United States. We found that species have divergent responses to light availability, with shade-intolerant species experiencing an alleviation of trade-offs at high light- and shade-tolerant species showing no changes in reproductive output across light environments. Correlations between temporal variation in individual growth and reproduction were weak and generally insensitive to canopy exposure, but changed when considering time lags. The diversity of responses across species indicates that reproductive allocation for trees in these forests is strongly influenced by both species’ life history and environmental heterogeneity in space and time.

Berdanier, Aaron B., Chelcy F. Miniat, and James S. Clark, (2016) Predictive models for radial sap flux variation in coniferous, diffuse-porous and ring-porous temperate trees Tree Physiol. 36 (8): 932-941 doi:10.1093/treephys/tpw027

Abstract
Accurately scaling sap flux observations to tree or stand levels requires accounting for variation in sap flux between wood types and by depth into the tree. However, existing models for radial variation in axial sap flux are rarely used because they are difficult to implement, there is uncertainty about their predictive ability and calibration measurements are often unavailable. Here we compare different models with a diverse sap flux data set to test the hypotheses that radial profiles differ by wood type and tree size. We show that radial variation in sap flux is dependent on wood type but independent of tree size for a range of temperate trees. The best-fitting model predicted out-of-sample sap flux observations and independent estimates of sapwood area with small errors, suggesting robustness in the new settings. We develop a method for predicting whole-tree water use with this model and include computer code for simple implementation in other studies.

Brantley, Steven T., Morgan L. Schulte, Paul V. Bolstad, and Chelcy F. Miniat. 2016. Equations for Estimating Biomass, Foliage Area, and Sapwood of Small Trees in the Southern Appalachians. Forest Science. 62(4)414-421. http://dx.doi.org/10.5849/forsci.15-041.

Abstract
Small trees and shrubs play an important role in forest diversity and regeneration and may contribute substantially to ecosystem fluxes of carbon and water; however, relatively little attention is given to quantifying the contribution of small trees to forest processes. One reason for this may be that the allometric equations developed for large trees tend to systematically underestimate structural variables such as biomass and foliage area when applied to small trees, both on an individual tree level and at the stand level. To test this hypothesis, we developed allometric equations for trees 10 cm dbh (D) for seven dependent variables (woody, foliage, and total biomass; woody, foliage, and whole-plant surface area; and sapwood area) and compared these new equations with the existing equations for large trees. We found significant differences between small tree and large tree equations for most variables and showed that equations for large trees tend to underestimate the structural characteristics of small trees. When we applied new size-specific equations to forest survey data representing a chronosequence of forest development, estimates of small tree biomass increased 30–73% and estimates of foliage area increased 72–142% compared with results using only equations for large trees. These results suggest that small trees can contribute substantially to forest structure and associated ecosystem fluxes, especially in stands with a large proportion of small trees. However, size-specific equations for small trees did not substantially change the estimates of forest biomass in these stands, and the need to develop size-specific equations may depend on the variables of interest.

Bruce, Richard C. 2016. Application of the Gompertz Function in Studies of Growth in Dusky Salamanders (Plethodontidae: Desmognathus). Copeia. 104(1):94-100. DOI: 10.1643/CE-14-204.

Abstract
Gompertz growth functions were fitted to skeletochronological data sets of three species of desmognathine salamanders from an assemblage (Wolf Creek) in the Cowee Mountains of southwestern North Carolina. The results were compared to earlier evaluations of growth in desmognathines from a nearby assemblage (Coweeta) in the Nantahala Mountains. In two of the species, Desmognathus quadramaculatus and D. monticola, larger adult body sizes were attained at Coweeta than at Wolf Creek, whereas adult body sizes of the third species, D. ocoee, were similar in the two populations. Growth in both standard length (snout–vent length) and body mass were evaluated. The early phases of growth, prior to sexual maturation, were similar in the larger D. quadramaculatus and the smaller D. monticola, and higher in both species than in the even smaller D. ocoee. In all three species, growth rates tended to be higher in the Coweeta populations than in those at Wolf Creek. The inflexions of the Gompertz curves for body mass versus age, representing the maximum rates of growth, occurred at or near the age of first reproduction, which is expected, given the tendency for growth to slow at sexual maturation in desmognathines and other salamanders. The results support earlier findings that differences in adult body size between D. quadramaculatus and D. monticola are mainly effects of differences in age at sexual maturation, modulated by a difference in propagule size, as opposed to growth differences. However, the difference in adult size between these species and D. ocoee are joint effects of smaller propagule size, lower growth rate, and earlier maturation in the latter species.

Caldwell, P. V., Miniat, C. F., Elliott, K. J., Swank, W. T., Brantley, S. T. and Laseter, S. H. (2016), Declining water yield from forested mountain watersheds in response to climate change and forest mesophication. Glob Change Biol, 22: 2997–3012. doi:10.1111/gcb.13309

Abstract
Climate change and forest disturbances are threatening the ability of forested mountain watersheds to provide the clean, reliable, and abundant fresh water necessary to support aquatic ecosystems and a growing human population. Here, we used 76 years of water yield, climate, and field plot vegetation measurements in six unmanaged, reference watersheds in the southern Appalachian Mountains of North Carolina, USA to determine whether water yield has changed over time, and to examine and attribute the causal mechanisms of change. We found that annual water yield increased in some watersheds from 1938 to the mid-1970s by as much as 55%, but this was followed by decreases up to 22% by 2013. Changes in forest evapotranspiration were consistent with, but opposite in direction to the changes in water yield, with decreases in evapotranspiration up to 31% by the mid-1970s followed by increases up to 29% until 2013. Vegetation survey data showed commensurate reductions in forest basal area until the mid-1970s and increases since that time accompanied by a shift in dominance from xerophytic oak and hickory species to several mesophytic species (i.e., mesophication) that use relatively more water. These changes in forest structure and species composition may have decreased water yield by as much as 18% in a given year since the mid-1970s after accounting for climate. Our results suggest that changes in climate and forest structure and species composition in unmanaged forests brought about by disturbance and natural community dynamics over time can result in large changes in water supply.

Chandler, R. & Hepinstall-Cymerman, J. (2016), Estimating the spatial scales of landscape effects on abundance, Landscape Ecol, 31:1383, doi:10.1007/s10980-016-0380-z

Abstract
Context Spatial variation in abundance is influenced by local- and landscape-level environmental variables, but modeling landscape effects is challenging because the spatial scales of the relationships are unknown. Current approaches involve buffering survey locations with polygons of various sizes and using model selection to identify the best scale. The buffering approach does not acknowledge that the influence of surrounding landscape features should diminish with distance, and it does not yield an estimate of the unknown scale parameters. Objectives The purpose of this paper is to present an approach that allows for statistical inference about the scales at which landscape variables affect abundance. Methods Our method uses smoothing kernels to average landscape variables around focal sites and uses maximum likelihood to estimate the scale parameters of the kernels and the effects of the smoothed variables on abundance. We assessed model performance using a simulation study and an avian point count dataset. Results The simulation study demonstrated that estimators are unbiased and produce correct confidence interval coverage except in the rare case in which there is little spatial autocorrelation in the landscape variable. Canada warbler abundance was more highly correlated with site-level measures of NDVI than landscape-level NDVI, but the reverse was true for elevation. Canada warbler abundance was highest when elevation in the surrounding landscape, defined by an estimated Gaussian kernel, was between 1300 and 1400 m. Conclusions Our method provides a rigorous way of formally estimating the scales at which landscape variables affect abundance, and it can be embedded within most classes of statistical models.

Clark, J. S. (2016), Why species tell more about traits than traits about species: predictive analysis. Ecology, 97: 1979–1993. doi:10.1002/ecy.1453

Abstract
Trait analysis aims to understand relationships between traits, species diversity, and the environment. Current methods could beneft from a model-based probabilistic framework that accommodates covariance between traits and quantifes contributions from inherent trait syndromes, species interactions, and responses to the environment. I develop a model-based approach that separates these effects on trait diversity. Application to USDA Forest Inventory and Analysis (FIA) data in the eastern United States demonstrates an apparent paradox, that the analysis of species better explains and predicts traits than does direct analysis of the traits themselves; trait data contain less, not more, information than species on environmental responses. Whereas variation in some traits is dominated by inherent syndromes (tendency for certain traits to be associated with others within an individual and species), others are strongly controlled by variation in species diversity. There is substantial variation in environmental control on trait patterns, between traits and regionally. In terms of environmental response traits do not aggregate into defned plant functional types, as would be desirable for models.

Coughlan, Michael R. and T.L. Gragson. 2016. An Event History Analysis of Parcel Extensification and Household Abandonment in Pays Basque, French Pyrenees, 1830–1958 AD. Human Ecology. DOI:10.1007/s10745-016-9808-y.

Abstract
This paper examines local processes of agricultural abandonment, socioeconomic changes, and associated landscape transition in a Pyrenean mountain village. We analyze the effects of socioeconomic and demographic factors contributing to changes in parcel level land use and ownership from 1830 to 1958. We use an event-history analysis to examine how individual etxe (Basque households) influenced the pace and character of landscape transition through their internal composition and their mediation of market pressures. Contrary to conventional narratives of agricultural transitions, our analysis suggests that more rapid "abandonment" of the landscape was prevented by etxe that were able to both engage in markets and maintain higher fertility rates. We conclude that the capacity of agropastoral landscapes to absorb broadscale change is directly tied to local institutions, such as the etxe, which ultimately mediate socioeconomic drivers of change.

Coughlan, Michael. R. 2016. Wildland Arson as Clandestine Resource Management: A Space-Time Permutation Analysis and Classification of Informal Fire Management Regimes in Georgia, USA. Environmental Management. DOI:10.1007/s00267-016-0669-3.

Abstract
Forest managers are increasingly recognizing the value of disturbance-based land management techniques such as prescribed burning. Unauthorized, ‘‘arson’’ fires are common in the southeastern United States where a legacy of agrarian cultural heritage persists amidst an increasingly forest-dominated landscape. This paper reexamines unauthorized fire-setting in the state of Georgia, USA from a historical ecology perspective that aims to contribute to historically informed, disturbance-based land management. A space–time permutation analysis is employed to discriminate systematic, management-oriented unauthorized fires from more arbitrary or socially deviant fire-setting behaviors. This paper argues that statistically significant space–time clusters of unauthorized fire occurrence represent informal management regimes linked to the legacy of traditional land management practices. Recent scholarship has pointed out that traditional management has actively promoted sustainable resource use and, in some cases, enhanced biodiversity often through the use of fire. Despite broad-scale displacement of traditional management during the 20th century, informal management practices may locally circumvent more formal and regionally dominant management regimes. Space–time permutation analysis identified 29 statistically significant fire regimes for the state of Georgia. The identified regimes are classified by region and land cover type and their implications for historically informed disturbance-based resource management are discussed.

Frisch, John R., Peterson, James T., Cecala, Kristen K., Maerz, John C., Jackson, C. Rhett, Gragson, Ted L., and Pringle, Catherine M. 2016. Patch occupancy of stream fauna across a land cover gradient in the southern Appalachians, USA. Hydrobiologia. 773:163-175. doi:10.1007/s10750-016-2695-9.

Abstract
We modeled patch occupancy to examine factors that best predicted the prevalence of four functionally important focal stream consumers (Tallaperla spp., Cambarus spp., Pleurocera proxima, and Cottus bairdi) among 37 reaches within the Little Tennessee River basin of the southern Appalachian Mountains, USA. We compared 34 models of patch occupancy to examine the association of catchment and reach scale factors that varied as a result of converting forest to agricultural or urban land use. Occupancy of our taxa was linked to parameters reflecting both catchment and reach extent characteristics. At the catchment level, forest cover or its conversion to agriculture was a major determinant of occupancy for all four taxa. Patch occupancies of Tallaperla, Cambarus, and C. bairdi were positively, and Pleurocera negatively, correlated with forest cover. Secondarily at the reach level, local availability of large woody debris was important for Cambarus, availability of large cobble substrate was important for C. bairdi, and stream calcium concentration was important for P. proxima. Our results show the abundance of stream organisms was determined by the taxon-dependent interplay between catchment- and reach-level factors.

Graves, R. A., S. M. Pearson, and M. G. Turner. 2016. Landscape patterns of bioenergy in a changing climate: implications for crop allocation and land-use competition. Ecological Applications 26:515-529. (http://dx.doi.org/10.1890/15-0545.1)

Abstract
Rural landscapes face changing climate, shifting development pressure, and loss of agricultural land. Perennial bioenergy crops grown on existing agricultural land may provide an opportunity to conserve rural landscapes while addressing increased demand for biofuels. However, increased bioenergy production and changing land use raise concerns for tradeoffs within the food-energy-environment trilemma. Heterogeneity of climate, soils, and land use complicate assessment of bioenergy potential in complex landscapes creating challenges to evaluating future tradeoffs. The hypothesis addressed herein is that perennial bioenergy production can provide an opportunity to avoid agricultural land conversion to development. Using a process-based crop model, we assessed potential bioenergy crop growth through 2100 in a southern Appalachian Mountain region and asked: (1) how mean annual yield differed among three crops (switchgrass, giant miscanthus, and hybrid poplar) under current climate and climate change scenarios resulting from moderate and very-high greenhouse gas emissions; (2) how maximum landscape yield, spatial allocation of crops, and bioenergy hotspots (areas with highest potential yield) varied among climate scenarios; and (3) how bioenergy hotspots overlapped with current crop production or lands with high development pressure. Under both climate change scenarios, mean annual yield of perennial grasses decreased (-4% to -39%), but yield of hybrid poplar increased (+8% to +20%) which suggests that a switch to woody crops would maximize bioenergy crop production. In total, maximum landscape yield increased by up to 90,000 Mg yr-1 (6%) in the 21st Century due to increased poplar production. Bioenergy hotspots (>18 Mg ha-1yr-1) consistently overlapped with high suburban/exurban development likelihood and existing row crop production. If bioenergy production is constrained to marginal (non-crop) lands, landscape yield decreased by 27%. The removal of lands with high development probability from crop production resulted in losses of up to 670,000 Mg yr-1 (40%). This study demonstrated that tradeoffs among bioenergy production, crop production, and exurban expansion in a mountainous changing rural landscape vary spatially with climate change over time. If markets develop, bioenergy crops could potentially counter losses of agricultural land to development.

Graves, R.A., Pearson, S.M. & Turner, M.G. (2017), Landscape dynamics of floral resources affect the supply of a biodiversity-dependent cultural ecosystem service, Landscape Ecol 32: 415. doi:10.1007/s10980-016-0452-0

Abstract
Context - Cultural ecosystem services, many of which depend on biodiversity, are recognized as important but seldom quantified biophysically across landscapes. Furthermore, many ecosystem service models are static, and the supply of cultural ecosystem services may be misrepresented if seasonal shifts in biotic communities are ignored. Objectives - We modeled landscape dynamics of wildflower blooms in a temperate montane landscape to determine (1) how floral resources (wildflower species richness, abundance, timing, and presence of charismatic species) changed over the growing season, (2) how projectedwildflower viewing hotspots varied over space and time, and (3) how spatial shifts in floral resources affected potential public access to wildflower viewing. Methods - Data were collected at 63 sites across a rural-to-urban gradient in the Southern Appalachian Mountains (USA). Generalized linear models were used to identify factors affecting floral resources at two temporal scales. Floral resources were projected across the landscape and hotspots of wildflower viewing were quantified using overlay analysis. Results - Floral resources were affected by topoedaphic conditions, climate, and surrounding building density and changed seasonally. Seasonal models revealed locational shifts in ecosystem service hotspots, which changed the proportion of hotspots accessible to the public and identified wildflowerviewing opportunities unnoticed by static models. Conclusion - Relationships between landscape gradients, biodiversity, and ecosystem service supply varied seasonally, and our models identified cultural ecosystem service hotspots otherwise obscured by simple proxies. Landscape models of biodiversity based cultural ecosystem services should include seasonal dynamics of biotic communities to avoid under- or over-emphasizing the importance of particular locations in ecosystem service assessments.

Grossman, G. D., Sundin, G. and Ratajczak, R. E. 2016. Long-term persistence, density dependence and effects of climate change on rosyside dace (Cyprinidae). Freshwater Biology, 61:832–847. doi:10.1111/fwb.12741.

Abstract
1. We used long-term population data for rosyside dace (Clinostomus funduloides), a numerically dominant member of a stochastically organised fish assemblage, to evaluate the relative importance of density-dependent and density-independent processes to population persistence. 2. We also evaluated the potential impacts of global climate change (GCC) on this species and predicted how directional environmental changes will affect dace. 3. We sampled two 30 m permanent sites in spring and autumn in the Coweeta catchment for rosyside dace density using three-pass electrofishing between 1984 and 1995, and a single 100 m site from 1991 to 2003. 4. Habitat availability and flow variation data for this 20-year period demonstrated that two droughts (1985–1988 and 1999–2002) produced smaller wetted areas, lower mean, maximum and minimum flows, fewer high flow events and greater amounts of depositional substrata in the sites. 5. Droughts produced significant increases in abundance, and significant decreases in standard length and mass of rosyside dace. Increases in abundance were mainly due to increased survival/ immigration of young-of-the-year (YOY). 6. Model selection analysis using multiple single and multivariable models indicated that density dependence in various forms possessed substantial explanatory power with respect to long-term variation in the per-capita rate of increase (r) in all sites and seasons. Density-dependent effects on r were stronger in autumn than spring, whereas negative density-independent models (flow variation) had the greatest explanatory power in spring. 7. Results for growth data were similar to those for rosyside dace density and confirm density dependence likely through intraspecific competition for food or foraging sites leading to reduced growth at higher densities. 8. These data support the hypothesis that species may persist in stochastic animal assemblages via strong intraspecific density dependence. Greater flow variability or increased high flows produced by GCC may destabilise this population leading to reduced compensation and possibly eventual extinction.

Hales, T. C., and Miniat, C. F. (2017) Soil moisture causes dynamic adjustments to root reinforcement that reduce slope stability. Earth Surf. Process. Landforms, 42: 803–813. doi: 10.1002/esp.4039.

Abstract
In steep soil-mantled landscapes, the initiation of shallow landslides is strongly controlled by the distribution of vegetation, whose roots reinforce the soil. The magnitude of root reinforcement depends on the number, diameter distribution, orientation and the mechanical properties of roots that cross potential failure planes. Understanding how these properties vary in space and time in forests remains a significant challenge. Here we test the hypothesis that spatio-temporal variations in root reinforcement along a hillslope occur as a function of topographic soil moisture gradients. To test this hypothesis we compared root reinforcement measurements from relatively dry, divergent noses to relatively wet, convergent hollows in the southern Appalachian Mountains, North Carolina, USA. Our initial results showed that root reinforcement decreased in areas of higher soil moisture because the tensile strength of roots decreased. A post hoc laboratory experiment further demonstrated that root tensile strength decreased as root moisture content increased. This effect is consistent with other experiments on stem woods showing that increased water content in the cell wall decreases tensile strength. Our experimental data demonstrated that roots can adjust to changes in the external root moisture conditions within hours, suggesting that root moisture content will change over the timescale of large storm events (hours–days). We assessed the effects of the dynamic changes in root tensile strength to the magnitude of apparent cohesion within the infinite slope stability model. Slopes can be considerably less stable when precipitation-driven increases in saturated soil depth both increase pore pressures and decrease root reinforcement.

Henriques Antão, L., Connolly, S. R., Magurran, A. E., Soares, A. and Dornelas, M. (2016), Prevalence of multimodal species abundance distributions is linked to spatial and taxonomic breadth. Global Ecol. Biogeogr.. doi:10.1111/geb.12532

Abstract
Species abundance distributions (SADs) are a synthetic measure of biodiversity and community structure. Although typically described by unimodal logseries or lognormal distributions, empirical SADs can also exhibit multiple modes. However, we do not know how prevalent multimodality is, nor do we have an understanding of the factors leading to this pattern. Here we quantify the prevalence of multimodality in SADs across a wide range of taxa, habitats and spatial extents.

Katherine J. Elliott, James M. Vose, (2016) Effects of riparian zone buffer widths on vegetation diversity in southern Appalachian headwater catchments, Forest Ecology and Management, Volume 376, Pages 9-23, ISSN 0378-1127, http://dx.doi.org/10.1016/j.foreco.2016.05.046.

Abstract
In mountainous areas such as the southern Appalachians USA, riparian zones are difficult to define. Vegetation is a commonly used riparian indicator and plays a key role in protecting water resources, but adequate knowledge of floristic responses to riparian disturbances is lacking. Our objective was to quantify changes in stand-level floristic diversity of riparian plant communities before (2004) and two, three, and seven years after shelterwood harvest using highlead cable-yarding and with differing nocut buffer widths of 0 m, 10 m, and 30 m distance from the stream edge. An unharvested reference stand was also studied for comparison. We examined: (1) differences among treatment sites using a mixed linear model with repeated measures; (2) multivariate relationships between ground-layer species composition and environmental variables (soil water content, light transmittance, tree basal area, shrub density, and distance from stream) using nonmetric multidimensional scaling; and (3) changes in species composition over time using a multi-response permutation procedure. We hypothesized that vegetation responses (i.e., changes in density, species composition, and diversity across the hillslope) will be greatest on harvest sites with an intermediate buffer width (10-m buffer) compared to more extreme (0-m buffer) and less extreme (30-m buffer and no-harvest reference) disturbance intensities. Harvesting initially reduced overstory density and basal area by 83% and 65%, respectively, in the 0-m buffer site; reduced by 50% and 74% in the 10-m buffer site; and reduced by 45% and 29% in the 30-m buffer site. Both the 0-m and 10-m buffer sites showed increased incident light variability across the hillslope after harvesting; whereas, there was no change in the 30-m and reference sites over time. We found significant changes in midstory and ground-layer vegetation in response to harvesting with the greatest responses on the 10-m buffer site, supporting our hypotheses that responses will be greatest on sites with intermediate disturbance. Ground-layer species composition differed significantly over time in the 0-m buffer and 10-m buffer sites (both P < 0.0001), but did not change in the 30-m buffer and reference sites (both P > 0.100). Average compositional dissimilarity increased after seven years, indicating greater withinstand heterogeneity (species diversity) after harvesting. These vegetation recovery patterns provide useful information for evaluating management options in riparian zones in the southern Appalachians

Keiser, A.D., Knoepp, J.D. & Bradford, M.A. (2016) Disturbance Decouples Biogeochemical Cycles Across Forests of the Southeastern US, Ecosystems 19: 50. doi:10.1007/s10021-015-9917-2

Abstract
Biogeochemical cycles are inherently linked through the stoichiometric demands of the organisms that cycle the elements. Landscape disturbance can alter element availability and thus the rates of biogeochemical cycling. Nitrification is a fundamental biogeochemical process positively related to plant productivity and nitrogen loss from soils to aquatic systems, and the rate of nitrification is sensitive to both carbon and nitrogen availability. Yet how these controls influence nitrification rates at the landscape scale is not fully elucidated. We, therefore, sampled ten watersheds with different disturbance histories in the southern Appalachian Mountains to examine effects on potential net nitrification rates. Using linear mixed model selection (AIC), we narrowed a broad suite of putative explanatory variables into a set of models that best explained landscape patterns in potential net nitrification. Forest disturbance history determined whether nitrification and nitrogen mineralization were correlated, with the effect apparently mediated by microbially available carbon. Undisturbed forests had higher available carbon, which uncoupled potential net nitrification from potential net nitrogen mineralization. In contrast, disturbed watersheds had lower available carbon, and nitrification rates were strongly correlated to those of nitrogen mineralization. These data suggest that a history of disturbance at the landscape scale reduces soil carbon availability, which increases ammonium availability to nitrifiers at the microscale. Landscape-level soil carbon availability then appears to determine the coupling of autotrophic (nitrification) and heterotrophic (nitrogen mineralization) biogeochemical processes, and hence the relationship between carbon and nitrogen cycling in soils.

Knoepp, Jennifer D.; Vose, James M.; Jackson, William A.; Elliott, Katherine J.; Zarnoch, Stan (2016) High elevation watersheds in the southern Appalachians: indicators of sensitivity to acidic deposition and the potential for restoration through liming. Forest Ecology and Management, Vol. 377: 17 pages.: 101-117. 10.1016/j.foreco.2016.06.040

Abstract
Southern Appalachian high elevation watersheds have deep rocky soils with high organic matter content, different vegetation communities, and receive greater inputs of acidic deposition compared to low elevation sites within the region. Since the implementation of the Clean Air Act Amendment in the 1990s, concentrations of acidic anions in rainfall have declined. However, some high elevation streams continue to show signs of chronic to episodic acidity, where acid neutralizing capacity (ANC) ranges from 0 to 20 leq L1. We studied three 3rd order watersheds (North River in Cherokee National Forest, Santeetlah Creek in Nantahala National Forest, and North Fork of the French Broad in Pisgah National Forest) and selected four to six 1st order catchments within each watershed to represent a gradient in elevation (849–1526 m) and a range in acidic stream ANC values (11–50 leq L1). Our objectives were to (1) identify biotic, physical and chemical catchment parameters that could be used as indices of stream ANC, pH and Ca:Al molar ratios and (2) estimate the lime required to restore catchments from the effects of excess acidity and increase base cation availability. We quantified each catchment’s biotic, physical, and chemical characteristics and collected stream, O-horizon, and mineral soil samples for chemical analysis seasonally for one year. Using repeated measures analysis, we examined variability in stream chemistry and catchment characteristics; we used a nested split-plot design to identify catchment characteristics that were correlated with stream chemistry. Watersheds differed significantly and the catchments sampled provided a wide range of stream chemical, biotic, physical and chemical characteristics. Variability in stream ANC, pH, and Ca:Al molar ratio were significantly correlated with catchment vegetation characteristics (basal area, tree height, and tree diameter) as well as O-horizon nitrogen and aluminum concentrations. Total soil carbon and calcium (an indicator of parent material), were significant covariates for stream ANC, pH and Ca:Al molar ratios. Lime requirement estimates did not differ among watersheds but this data will help select catchments for future restoration and lime application studies. Not surprisingly, this work found many vegetation and chemical characteristics that were useful indicators of stream acidity. However, some expected relationships such as concentrations of mineral soil extractable Ca and SO4 were not significant. This suggests that an extensive test of these indicators across the southern Appalachians will be required to identify high elevation forested catchments that would benefit from restoration activities

Manning, D.W.P, A.D. Rosemond, J.P. Benstead, J.S. Kominoski, V. Gulis, and J.C. Maerz (2016), Convergence of detrital stoichiometry predicts thresholds of nutrient-stimulated breakdown in streams. Ecological Applications. 26(6):1745-1757. DOI:10.1890/15-1217.1.

Abstract
Nutrient enrichment of detritus-based streams increases detrital resource quality for consumers and stimulates breakdown rates of particulate organic carbon (C). The relative importance of dissolved inorganic nitrogen (N) vs. phosphorus (P) for detrital quality and their effects on microbial- vs. detritivore-mediated detrital breakdown are poorly understood. Here, we tested effects of experimental N and P additions on detrital stoichiometry (C:N, C:P) and total and microbial breakdown (i.e., with and without detritivorous shredders, respectively) of five detritus types (four leaf litter species and wood) with different initial C:nutrient content. We enriched five headwater streams continuously for two years at different relative availabilities of N and P and compared breakdown rates and detrital stoichiometry to pretreatment conditions. Total breakdown rates increased with nutrient enrichment and were predicted by altered detrital stoichiometry. Streamwater N and P, fungal biomass, and their interactions affected stoichiometry of detritus. Streamwater N and P decreased detrital C:N, whereas streamwater P had stronger negative effects on detrital C:P. Nutrient addition and fungal biomass reduced C:N by 70% and C:P by 83% on average after conditioning, compared to only 26% for C:N and 10% for C:P under pretreatment conditions. Detritus with lowest initial nutrient content changed the most, and had greatest increases in total breakdown rates. Detrital stoichiometry was reduced and differences among detritus types were homogenized by nutrient enrichment. With enrichment, detrital nutrient content approached detritivore nutritional requirements, and stimulated greaterAccepted Article This article is protected by copyright. All rights reserved. detritivore vs. microbial litter breakdown. We used breakpoint regression to estimate values of detrital stoichiometry that can potentially be used to indicate elevated breakdown rates. Breakpoint ratios for total breakdown were 41 (C:N) and 1518 (C:P), coinciding with total breakdown rates that were ~1.9× higher when C:N or C:P fell below these breakpoints. Microbial and shredder-mediated breakdown rates both increased when C:N and C:P were reduced, suggesting that detrital stoichiometry is useful for predicting litter breakdown dominated by either microbial or shredder activity. Our results show strong effects of nutrient enrichment on detrital stoichiometry and offer a robust link between a potential holistic nutrient loading metric (decreased and homogenized detrital stoichiometry) and increased C loss from stream ecosystems.

McEntire, Kira D. 2016. Arboreal Ecology of Plethodontidae: A Review. Copeia, 104(1):124-131. http://dx.doi.org/10.1643/OT-14-214.

Abstract
Lungless salamanders in the family Plethodontidae are widely distributed and the most diverse lineage of caudates. Plethodontids occupy forested and freshwater habitats, where they can achieve remarkable abundance and biomass. The majority of tropical plethodontids are arboreal. Though generally considered ground dwelling, a large proportion of temperate species have been observed climbing shrubs, trees, and herbaceous vegetation. Approximately 45% of terrestrial and semi-aquatic (not including permanently aquatic) plethodontid species are known to obligately or facultatively climb vegetation; yet, with the exception of tropical plethodontids, the importance of arboreal habits is generally underappreciated. The potential benefits of arboreality vary based on life history and geography but may include improved olfaction, increased foraging potential, shelter and nesting, and predator avoidance. Constraints on arboreality include increased water loss rates and morphological limitations. Recognition of arboreal habits as a relevant component of salamander ecology is important in rapidly changing landscapes with anthropogenic alterations to midstory and canopy communities.

Nippgen, F., B. L. McGlynn, R. E. Emanuel, and J. M. Vose (2016), Watershed memory at the Coweeta Hydrologic Laboratory: The effect of past precipitation and storage on hydrologic response, Water Resour.Res., 52, 1673–1695, doi:10.1002/2015WR018196.

Abstract
The rainfall-runoff response of watersheds is affected by the legacy of past hydroclimatic conditions. We examined how variability in precipitation affected streamflow using 21 years of daily streamflow and precipitation data from five watersheds at the Coweeta Hydrologic Laboratory in southwestern North Carolina, USA. The gauged watersheds contained both coniferous and deciduous vegetation, dominant north and south aspects, and differing precipitation magnitudes. Lag-correlations between precipitation and runoff ratios across a range of temporal resolutions indicated strong influence of past precipitation (i.e., watershed memory). At all time-scales, runoff ratios strongly depended on the precipitation of previous time steps. At monthly time scales, the influence of past precipitation was detectable for up to 7 months. At seasonal time scales, the previous season had a greater effect on a season’s runoff ratio than the same season’s precipitation. At annual time scales, the previous year was equally important for a year’s runoff ratio than the same year’s precipitation. Estimated watershed storage through time and specifically the previous year’s storage state was strongly correlated with the residuals of a regression between annual precipitation and annual runoff, partially explaining observed variability in annual runoff in watersheds with deep soils. This effect was less pronounced in the steepest watershed that also contained shallow soils. We suggest that the location of a watershed on a nonlinear watershed-scale storage-release curve can explain differences in runoff during growing and dormant season between watersheds with different annual evapotranspiration.

Norman, J.S., and J.E. Barrett. 2016. Substrate availability drives local patterns in richness of ammonia-oxidizing bacteria and archaea in temperate forest soils. Soil Biology and Biochemistry. 94:169-172. doi:10.1016/j.soilbio.2015.11.015.

Abstract
We sought to investigate the drivers of richness of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in temperate forest soils. We sampled soils across four experimental watersheds in the Coweeta Hydrologic Laboratory, North Carolina USA. These watersheds are geographically close, but vary in soil chemistry due to differences in land use history. While we found a positive relationship between soil pH and AOB richness in the soils we sampled, we provide evidence that this relationship is driven by the effects of soil pH on the availability of NH3, which is the substrate that is directly oxidized by AOB. Conversely, AOA richness responded to NH4+ which these organisms may access directly from the environment. Our results provide evidence that substrate availability may be a dominant driver of both AOA and AOB richness at local scales in forest soils.

Novick, K. A., Oishi, A. C. and Miniat, C. F. (2016), Cold air drainage flows subsidize montane valley ecosystem productivity. Glob Change Biol. doi:10.1111/gcb.13320

Abstract
In mountainous areas, cold air drainage from high to low elevations has pronounced effects on local temperature, which is a critical driver of many ecosystem processes, including carbon uptake and storage. Here, we leverage new approaches for interpreting ecosystem carbon flux observations in complex terrain to quantify the links between macro-climate condition, drainage flows, local microclimate, and ecosystem carbon cycling in a southern Appalachian valley. Data from multiple long-running climate stations and multiple eddy covariance flux towers are combined with simple models for ecosystem carbon fluxes. We show that cold air drainage into the valley suppresses local temperature by several degrees at night and for several hours before and after sunset, leading to reductions in growing season respiration on the order of ~8%. As a result, we estimate that drainage flows increase growing season and annual net carbon uptake in the valley by >10% and >15%, respectively, via effects on microclimate that are not be adequately represented in regional- and global-scale terrestrial ecosystem models. Analyses driven by chamberbased estimates of soil and plant respiration reveal cold air drainage effects on ecosystem respiration are dominated by reductions to the respiration of aboveground biomass. We further show that cold air drainage proceeds more readily when cloud cover and humidity are low, resulting in the greatest enhancements to net carbon uptake in the valley under clear, cloud-free (i.e., drought-like) conditions. This is a counterintuitive result that is neither observed nor predicted outside of the valley, where nocturnal temperature and respiration increase during dry periods. This result should motivate efforts to explore how topographic flows may buffer eco-physiological processes from macroscale climate change.

Novick, K.A., Miniat, C.F. and Vose, J.M. (2016). Drought limitations to leaf-level gas exchange: results from a model linking stomatal optimization and cohesion tension theory. Plant Cell and Environment. 39:583-596. DOI: 10.1111/pce.12657

Abstract
We merge concepts from stomatal optimization theory and cohesion-tension theory to examine the dynamics of three mechanisms that are potentially limiting to leaf-level gas exchange in trees during drought: a) a ‘demand limitation’ driven by an assumption of optimal stomatal functioning, b) ‘hydraulic limitation’ of water movement from the roots to the leaves, and c) ‘non-stomatal’ limitations imposed by declining leaf water status within the leaf. Model results suggest that species-specific ‘economics’ of stomatal behavior may play an important role in differentiating species along the continuum of isohydric to anisohydric behavior; specifically, we show that non-stomatal and demand limitations may reduce stomatal conductance and increase leaf water potential, promoting wide safety margins characteristic of isohydric species. We used model results to develop a diagnostic framework to identify the most likely limiting mechanism to stomatal functioning during drought, and showed that many of those features were commonly observed in field observations of tree water use dynamics. Direct comparisons of modeled and measured stomatal conductance further indicated that non-stomatal and demand limitations reproduced observed patterns of tree water use well for an isohydric species, but that a hydraulic limitation likely applies in the case of an anisohydric species.

Qualls, R.G. (2016),Long-Term (13 Years) Decomposition Rates of Forest Floor Organic Matter on Paired Coniferous and Deciduous Watersheds with Contrasting Temperature Regimes. Forests, 7, 231. 10.3390/f7100231

Abstract
Two sets of paired watersheds on north and South facing slopes were utilized to simulate the effects of temperature differences that are on the scale of those expected with near-term climatic warming on decomposition. Two watersheds were pine plantations (Pinus strobus L.) and two were mature deciduous forests established at similar elevation ranges and precipitation at the Coweeta Hydrologic Laboratory, but they differed in slope aspect (north vs. South facing), solar radiation, and litter temperature by about 2.0 °C. Nylon netting was placed on plots each year for 13 years and litterfall was measured. This time span in which decomposition rate was measured encompassed the time until less than 8% of the initial C remained. Decomposition rates of foliar litter were significantly faster on the slightly warmer watersheds, in both the coniferous and deciduous forests (Analysis of Variance). The turnover rate (year-1) was 0.359 (±0.006) for the South facing vs. 0.295 (±0.011) for the North facing coniferous watersheds, and 0.328 (±0.011) vs. 0.297 (±0.012) for the corresponding deciduous watersheds. Turnover rates of pine vs. deciduous broadleaf litter over 13 years were not significantly different because of the high proportion of relatively refractory Quercus spp. in the deciduous litterfall and because of a trend towards convergence of the rates after two years. After a greater decomposition rate in the first year or two, years 2–13 fit a negative exponential curve well (a timespan not well represented in literature) and there was only a small accumulation of humus older than 13 years. The fate of C in litterfall in the South facing deciduous forest was as follows: 14.3% was lost as leaching of dissolved organic C, 2.2% was lost as downward fine particulate matter flux from the bottom of the forest floor, 78.2% was mineralized (by mass balance), leaving only 5.4% of foliar litter after 13 years of decomposition. In these soils with a mor type O horizon, there was evidence that translocation of DOC and in-situ root production must be more important sources of mineral soil organic matter than downward migration of particulate humus.

Record, S., P. F. B. Ferguson, E. Benveniste, R. A. Graves, V. W. Pfeiffer, M. Romolini, C. E. Yorke, and B. Beardmore. 2015. Graduate students navigating social-ecological research: insights from the Long-Term Ecological Research Network. Ecology and Society 21(1):7. http://dx.doi.org/10.5751/ES-08111-210107

Abstract
Interdisciplinary, collaborative research capable of capturing the feedbacks between biophysical and social systems can improve the capacity for sustainable environmental decision making. Networks of researchers provide unique opportunities to foster social-ecological inquiry. Although insights into interdisciplinary research have been discussed elsewhere, they rarely address the role of networks and often come from the perspectives of more senior scientists. We have provided graduate student perspectives on interdisciplinary degree paths from within the Long-Term Ecological Research (LTER) Network. Focusing on data from a survey of graduate students in the LTER Network and four self-identified successful graduate student research experiences, we examined the importance of funding, pedagogy, research design and development, communication, networking, and culture and attitude to students pursuing social-ecological research. Through sharing insights from successful graduate student approaches to social-ecological research within the LTER Network, we hope to facilitate dialogue between students, faculty, and networks to improve training for interdisciplinary scientists.

Rice, Joshua S., R.E. Emanuel, and J.M. Vose. 2016. The influence of watershed characteristics on spatial patterns of trends in annual scale streamflow variability in the continental U.S., Journal of Hydrology. 540:850-860. http://dx.doi.org/10.1016/j.jhydrol.2016.07.006

Abstract
As human activity and climate variability alter the movement of water through the environment the need to better understand hydrologic cycle responses to these changes has grown. A reasonable starting point for gaining such insight is studying changes in streamflow given the importance of streamflow as a source of renewable freshwater. Using a wavelet assisted method we analyzed trends in the magnitude of annual scale streamflow variability from 967 watersheds in the continental U.S. (CONUS) over a 70 year period (1940–2009). Decreased annual variability was the dominant pattern at the CONUS scale. Ecoregion scale results agreed with the CONUS pattern with the exception of two ecoregions closely divided between increases and decreases and one where increases dominated. A comparison of trends in reference and non-reference watersheds indicated that trend magnitudes in non-reference watersheds were significantly larger than those in reference watersheds. Boosted regression tree (BRT) models were used to study the relationship between watershed characteristics and the magnitude of trends in streamflow. At the CONUS scale, the balance between precipitation and evaporative demand, and measures of geographic location were of high relative importance. Relationships between the magnitude of trends and watershed characteristics at the ecoregion scale exhibited differences from the CONUS results and substantial variability was observed among ecoregions. Additionally, the methodology used here has the potential to serve as a robust framework for top-down, data driven analyses of the relationships between changes in the hydrologic cycle and the spatial context within which those changes occur.

Richard C. Bruce (2016) Relative Growth Rates in Three Species of Desmognathus (Amphibia: Plethodontidae). Herpetologica: September 2016, Vol. 72, No. 3, pp. 174-180, https://doi.org/10.1655/Herpetologica-D-15-00060.1

Abstract
Observed life histories of animals reflect trade-offs among growth, reproduction, and survival that serve to maximize fitness under particular environmental regimes. Body size and age at first reproduction, as expressions of growth and developmental rates, are key trade-off elements. I estimated relative growth rates in three species of desmognathine salamanders that vary markedly in body size and habitat associations. Sampling was conducted in two assemblages of the species in the southern Blue Ridge of North Carolina. The species, ranked from larger to smaller, were Desmognathus quadramaculatus, D. monticola, and D. ocoee. An existing skeletochronological database served as a source of age estimates in salamanders for which standard lengths had been recorded. Body masses were estimated for these individuals from regressions of mass on standard length. Relative growth rates were estimated by the Gompertz model for growth in standard length and body mass, and by the von Bertalanffy model for growth in body mass only. In young salamanders, higher relative growth rates were recorded in the smaller species; this trend reversed at later ages wherein relative growth rates were greater in larger species over the remainder of the salamanders' life spans. In all three species in both assemblages, the maximum rates of absolute growth in mass occurred near or within the conjoint age range at first reproduction of the two sexes. Body size differences among these species result from differences in propagule size, growth rate, and (as one index of reproductive effort) age at sexual maturation. I present evidence that larger adult body sizes are a product of larger eggs, larger hatchlings, higher rates of growth, and lower reproductive effort in these and other species of Desmognathus, in southern Appalachian assemblages of the genus.

Rose, K. C., Graves, R. A., Hansen, W. D., Harvey, B. J., Qiu, J., Wood, S. A., Ziter, C. and Turner, M. G. (2017), Historical foundations and future directions in macrosystems ecology. Ecol Lett, 20: 147–157.

Abstract
Macrosystems ecology is an effort to understand ecological processes and interactions at the broadest spatial scales and has potential to help solve globally important social and ecological challenges. It is important to understand the intellectual legacies underpinning macrosystems ecology: How the subdiscipline fits within, builds upon, differs from and extends previous theories. We trace the rise of macrosystems ecology with respect to preceding theories and present a new hypothesis that integrates the multiple components of macrosystems theory. The spatio-temporal anthropogenic rescaling (STAR) hypothesis suggests that human activities are altering the scales of ecological processes, resulting in interactions at novel space–time scale combinations that are diverse and predictable. We articulate four predictions about how human actions are “expanding”, “shrinking”, “speeding up” and “slowing down” ecological processes and interactions, and thereby generating new scaling relationships for ecological patterns and processes. We provide examples of these rescaling processes and describe ecological consequences across terrestrial, freshwater and marine ecosystems. Rescaling depends in part on characteristics including connectivity, stability and heterogeneity. Our STAR hypothesis challenges traditional assumptions about how the spatial and temporal scales of processes and interactions operate in different types of ecosystems and provides a lens through which to understand macrosystem-scale environmental change.

Singh N.K., Reyes W.M., Bernhardt E.S., Bhattacharya R., Meyer J.L., Knoepp J.D., Emanuel R.E. 2016. Hydro-Climatological Influences on Long-Term Dissolved Organic Carbon in a Mountain Stream of the Southeastern United States. Journal of Environmental Quality. 45:1286-1295. doi:10.2134/jeq2015.10.0537

Abstract
In the past decade, significant increases in surface water dissolved organic carbon (DOC) have been reported for large aquatic ecosystems of the Northern Hemisphere and have been attributed variously to global warming, altered hydrologic conditions, and atmospheric deposition, among other factors. We analyzed a 25-yr DOC record (1988–2012) available for a forested headwater stream in the United States and documented two distinct regimes of stream DOC trends. From 1988 to 2001, annual mean volume-weighted DOC concentration (DOCvw, mg L-1) and annual DOC flux (kg ha-1 yr-1) declined by 34 and 56%, respectively. During 1997 to 2012, the decline in DOCvw and DOC flux increased by 141 and 165%, respectively. Declining DOCvw from 1988 to 2001 corresponded to a decline in growing season runoff, which has the potential to influence mobilization of DOC from uplands to streams. Increasing DOCvw from 1997 to 2012 corresponded to increased precipitation early in the growing season and to an increase in the number and intensity of shortduration fall storms capable of mobilizing long-accrued DOC from forest litter and soils. In contrast, total annual runoff declined throughout the period. Rising air temperature, atmospheric acid deposition, and nitrogen depositions did not offer any plausible explanation for the observed bidirectional annual trends of stream DOCvw. Our study highlights the critical role of long-term datasets and analyses for understanding the impacts of climate change on carbon and water cycles and associated functions of aquatic and terrestrial ecosystems.

Singh, N. K., R. E. Emanuel, and B. L. McGlynn (2016), Variability in isotopic composition of base flow in two headwater streams of the southern Appalachians, Water Resour. Res., 52, 4264–4279, doi:10.1002/2015WR018463

Abstract
We investigated the influence of hillslope scale topographic characteristics and the relative position of hillslopes along streams (i.e., internal catchment structure) on the isotopic composition of base flow in first-order, forested headwater streams at Coweeta Hydrologic Laboratory. The study focused on two adjacent forested catchments with different topographic characteristics. We used stable isotopes (18O and 2H) of water together with stream gauging and geospatial analysis to evaluate relationships between internal catchment structure and the spatiotemporal variability of base flow d18O. Base flow d18O was variable in space and time along streams, and the temporal variability of base flow d18O declined with increasing drainage area. Base flow became enriched in 18O moving along streams from channel heads to catchment outlets but the frequency of enrichment varied between catchments. The spatiotemporal variability in base flow d18O was high adjacent to large hillslopes with short flow paths, and it was positively correlated with the relative arrangement of hillslopes within the catchment. These results point to influence of unique arrangement of hillslopes on the patterns of downstream enrichment. Spatial variability in base flow d18O within the streams was relatively low during dry and wet conditions, but it was higher during the transition period between dry and wet conditions. These results suggest that the strength of topographic control on the isotopic composition of base flow can vary with catchment wetness. This study highlights that topographic control on base flow generation and isotopic composition is important even at fine spatial scales.

Vose, J.M., and K.J. Elliott. (2016). Oak, fre, and global change in the eastern USA: what might the future hold? Fire Ecology 12(2): 160–179. doi: 10.4996/freecology.1202160

Abstract
The pace of environmental and socioeconomic change over the past 100 years has been rapid. Changes in fire regimes, climate, and land use have shaped the structure and function of most forest ecosystems, including oak (Quercus spp. L.) forests in the eastern United States. New stressors such as air pollution and invasive species have contributed to and interacted with climate and fre to alter current forest conditions. While changing fire regimes have altered species composition of the current forest, oak regeneration is constrained by many factors that may affect future forests. Over the remainder of the twenty-frst century, an accelerating pace of climate and socioeconomic changes will in?uence the future range of variation in eastern oak forests. Some of these impacts will be direct, such as changes in tree growth rates, while other impacts will be indirect, such as new disturbance regimes. While it is likely that fre will be important in shaping oak forests in the twenty-frst century, it is less clear exactly what that role will be. For example, it is uncertain whether our current scientifc knowledge on the use of prescribed fire in oak forests will be applicable under novel climate and changing socioeconomic conditions. We propose that the combination of climate change, wildfre, and other disturbances will create stand conditions that favor oaks with or without management. However, management intervention (e.g., prescribed fire, thinning, or a combination) could reduce wildfre hazard, particularly in the wildland-urban interface, and create more desirable stand conditions that are resilient to future stressors such as changing precipitation patterns and warmer temperatures.

Vose, J.M., et al. Ecohydrological implications of drought for forests in the United States. Forest Ecol. Manage. (2016), http://dx.doi.org/10.1016/j.foreco.2016.03.025

Abstract
The relationships among drought, surface water flow, and groundwater recharge are not straightforward for most forest ecosystems due to the strong role that vegetation plays in the forest water balance. Hydrologic responses to drought can be either mitigated or exacerbated by forest vegetation depending upon vegetation water use and how forest population dynamics respond to drought. Understanding how drought impacts ecosystems requires understanding how drought impacts ecohydrological processes. Because different species and functional groups vary in their ecophysiological traits that influence water use patterns, changes in species assemblages can alter hydrological processes from the stand to the watershed scales. Recent warming trends and more prolonged and frequent droughts have accelerated the spread and intensity of insect attacks in the western US that kill nearly all of the canopy trees within forest stands, changing the energy balance of the land surface and affecting many hydrologic processes. In contrast, some eastern forest tree species and size classes can tolerate drought better than others, suggesting the potential for drought-mediated shifts in both species composition and structure. Predicting how these changes will impact hydrologic processes at larger spatial and temporal scales presents a considerable challenge. The biogeochemical consequences of drought, such as changes in stream chemistry, are closely linked to vegetation dynamics and hydrologic responses. As with other natural disturbances, droughts are difficult to prepare for because they are unpredictable. However, there are management options that may be implemented to minimize the impacts of drought on water quantity and quality. Examples include reducing leaf area by thinning and regenerating cut forests with species that consume less water, although a high level of uncertainty in both drought projections and anticipated responses suggests the need for monitoring and adaptive management.

Warren RJ, II (2016) Ghosts of Cultivation Past - Native American Dispersal Legacy Persists in Tree Distribution. PLoS ONE 11(3): e0150707. doi:10.1371/journal.pone.0150707.

Abstract
A long-term assumption in ecology is that species distributions correspond with their niche requirements, but evidence that species can persist in unsuitable habitat for centuries undermines the link between species and habitat. Moreover, species may be more dependent on mutualist partners than specific habitats. Most evidence connecting indigenous cultures with plant dispersal is anecdotal, but historical records suggest that Native Americans transported and cultivated many species, including Gleditsia triacanthos ("Honey locust"). Gleditsia triacanthos was an important medicinal/culinary (e.g., sugar), cultural (e.g., game sticks) and spiritual tree for the Cherokee (southeastern U.S. Native Americans). This study tests the hypothesis that a Cherokee cultivation legacy drives current regional G. triacanthos distribution patterns. Gleditsia triacanthos occurs in rocky uplands and xeric fields, but inexplicably also occurs in mesic riverine corridors and floodplains where Cherokee once settled and farmed. I combined field experiments and surveys in the Southern Appalachian Mountain region (U.S.) to investigate G. triacanthos recruitment requirements and distribution patterns to determine whether there is a quantifiable G. triacanthos association with former Cherokee settlements. Moreover, I also investigated alternate dispersal mechanisms, such as stream transport and domestic cattle. The results indicate that a centuries-old legacy of Native American cultivation remains intact as G. triacanthos' current southern Appalachian distribution appears better explained Cherokee settlement patterns than habitat. The data indicate that the tree is severely dispersal limited in the region, only moving appreciable distances from former Cherokee settlements where cattle grazing is prevalent. Human land use legacy may play a long-term role in shaping species distributions, and pre-European settlement activity appears underrated as a factor influencing modern tree species distributions.

Webster, J. R., Knoepp, J. D., Swank, W. T., Miniat, C. F. (2016), Evidence for a Regime Shift in Nitrogen Export from a Forested Watershed, Ecosystems, 19:5:881-895, DOI: 10.1007/s10021-016-9974-1

Abstract
In this study, we document a functional regime shift in stream inorganic nitrogen (N) processing indicated by a major change in N export from a forested watershed. Evidence from 36 years of data following experimental clearcut logging at Coweeta Hydrologic Laboratory, NC, suggests that forest disturbance in this area can cause elevation of dissolved inorganic N (DIN) loss lasting decades or perhaps longer. This elevation of N export was apparently caused by an initial pulse of organic matter input, reduced vegetation uptake, increased mineralization of soil organic N, and N fixation by black locust-associated bacteria following clearcut logging. In forested reference watersheds at Coweeta, maximum DIN concentration occurs in summer when base flow is low, but the clearcut watershed shifted to a pattern of maximum winter DIN concentration. The seasonal pattern of DIN concentration and export from reference watersheds can be explained by terrestrial and in-stream processes, but following clearcutting, elevated DIN availability saturated both terrestrial and in-stream uptake, and the N export regime became dominated by hydrologic transport. We suggest that the long-term elevation of stream DIN concentration and export along with the changes in seasonality of DIN export and the relationship between concentration and discharge represent a functional regime shift initiated by forest disturbance.

Xu, M. (2016), Ecological scaling laws link individual body size variation to population abundance fluctuation. Oikos, 125: 288–299. doi:10.1111/oik.03100

Abstract
Scaling research has seen remarkable progress in the past several decades. Many scaling relationships were discovered within and across individual and population levels, such as species–abundance relationship, Taylor's law, and density mass allometry. However none of these established patterns incorporate individual variation in the formulation. Individual body size variation is a key evolutionary phenomenon and closely related to ecological diversity and species adaptation. Using a macroecological approach, I test 57 Long-Term Ecological Research data sets and show that a power-law and a generalized power-law function describe well the mean-variance scaling of individual body mass. This relationship connects Taylor's law and density mass allometry, and leads to a new scaling pattern between the individual body size variation and population abundance fluctuation, which is confirmed using freshwater fish and forest tree data. Underlying mechanisms and implications of the proposed scaling relationships are discussed. This synthesis shows that integration and extension of existing ecological laws can lead to the discovery of new scaling patterns and complete our understanding of the relation between individual trait and population abundance. Scaling relationships are useful for community ecology as they reveal ubiquitous patterns across different levels of biological organizations. This work extends and integrates two existing scaling laws: Taylor’s law and densitymass allometry, and derives a new variance allometry between individual body mass and population abundance.

Amy D. Rosemond, Jonathan P. Benstead, Phillip M. Bumpers, Vladislav Gulis, John S. Kominoski, David W. P. Manning, Keller Suberkropp, and J. Bruce Wallace. 2015. Experimental nutrient additions accelerate terrestrial carbon loss from stream ecosystems. Science. 347:1142-1145. DOI:10.1126/science.aaa1958.

Abstract
Nutrient pollution of freshwater ecosystems results in predictable increases in carbon (C) sequestration by algae. Tests of nutrient enrichment on the fates of terrestrial organic C, which supports riverine food webs and is a source of CO2, are lacking. Using whole-stream nitrogen (N) and phosphorus (P) additions spanning the equivalent of 27 years, we found that average terrestrial organic C residence time was reduced by ~50% as compared to reference conditions as a result of nutrient pollution. Annual inputs of terrestrial organic C were rapidly depleted via release of detrital food webs from N and P co-limitation. This magnitude of terrestrial C loss can potentially exceed predicted algal C gains with nutrient enrichment across large parts of river networks, diminishing associated ecosystem services.

Boll, Jan, Erin S. Brooks, Brian Crabtree, Shuhui Dun, and Tammo S. Steenhuis, 2015. Variable Source Area Hydrology Modeling with the Water Erosion Prediction Project Model. Journal of the American Water Resources Association (JAWRA) 51(2): 330-342. DOI: 10.1111/1752-1688.12294.

Abstract
In nondegraded watersheds of humid climates, subsurface flow patterns determine where the soil saturates and where surface runoff is occurring. Most models necessarily use infiltration-excess (i.e., Hortonian) runoff for predicting runoff and associated constituents because subsurface flow algorithms are not included in the model. In this article, we modify the Water Erosion Prediction Project (WEPP) model to simulate subsurface flow correctly and to predict the spatial and temporal location of saturation, the associated lateral flow and surface runoff, and the location where the water can re-infiltrate. The modified model, called WEPP-UI, correctly simulated the hillslope drainage data from the Coweeta Hydrologic Laboratory hillslope plot. We applied WEPP-UI to convex, concave, and S-shaped hillslope profiles, and found that multiple overland flow elements are needed to simulate distributed lateral flow and runoff well. Concave slopes had the greatest runoff, while convex slopes had the least. Our findings concur with observations in watersheds with saturation-excess overland flow that most surface runoff is generated on lower concave slopes, whereas on convex slopes runoff infiltrates before reaching the stream. Since the WEPP model is capable of simulating both saturation-excess and infiltration-excess runoff, we expect that this model will be a powerful tool in the future for managing water quality.

Brian J. Burke, Meredith Welch-Devine, Seth Gustafson, Nik Heynen, Jennifer L. Rice, Ted L. Gragson, Sakura R. Evans & Donald R. Nelson (2015): Can Science Writing Collectives Overcome Barriers to More Democratic Communication and Collaboration? Lessons from Environmental Communication Praxis in Southern Appalachia, Environmental Communication, DOI: 10.1080/17524032.2014.999695

Abstract
Despite compelling reasons to involve nonscientists in the production of ecological knowledge, cultural and institutional factors often dis-incentivize engagement between scientists and nonscientists. This paper details our efforts to develop a biweekly newspaper column to increase communication between ecological scientists, social scientists, and the communities within which they work. Addressing communitygenerated topics and written by a collective of social and natural scientists, the column is meant to foster public dialog about socio-environmental issues and to lay the groundwork for the coproduction of environmental knowledge. Our collective approach to writing addresses some major barriers to public engagement by scientists, but the need to insert ourselves as intermediaries limits these gains. Overall, our efforts at environmental communication praxis have not generated significant public debate, but they have supported future coproduction by making scientists a more visible presence in the community and providing easy pathways for them to begin engaging the public. Finally, this research highlights an underappreciated barrier to public engagement: scientists are not merely disconnected from the public, but also connected in ways that may be functional for their research. Many field scientists, for example, seek out neutral and narrowly defined connections that permit research access but are largely incompatible with efforts to address controversial issues of environmental governance.

Burke, B.J., Welch-Devine, M. and Gustafson, S. 2015. Nature Talk in an Appalachian Newspaper: What Environmental Discourse Analysis Reveals about Efforts to Address Exurbanization and Climate Change. Human Organization. 74(2):185-196.

Abstract
As the people of Southern Appalachia confront the challenges of climate change and exurban development, their foundational beliefs about the environment and human-environment relations will significantly shape the types of individual and collective action that they imagine and pursue. In this paper, we use critical discourse analysis of an influential small-town newspaper to understand how the environment is being represented publicly and consider how these representations might affect local environmental politics and efforts to mitigate or adapt to climate change and exurban sprawl. We find that the environment is generally represented as an amenity to be enjoyed rather than a subject of concern, that environmental degradation, when represented at all, is often discussed in vague or distancing terms, and that human agency is typically presented in individualizing, hyper-local terms rather than in collective, community- or national-scale ones. In conclusion, we suggest that these representational styles are likely very effective for inspiring interest in and connection to local landscapes, but they do not provide a strong basis for collective efforts to understand and address climate change and exurbanization

Caldwell, P.V., Kennen, J.G., Sun, G., Kiang, J.E., Butcher, J.B., Eddy, M.C., Hay, L.E., LaFontaine, J.H., Hain, E.F., Nelson, S.A. and McNulty, S.G. 2015. A comparison of hydrologic models for ecological flows and water availablity. Ecohydrology. (DOI: 10.1002/eco.1602)

Abstract
Robust hydrologic models are needed to help manage water resources for healthy aquatic ecosystems and reliable water supplies for people, but there is a lack of comprehensive model comparison studies that quantify differences in streamflow predictions among model applications developed to answer management questions. We assessed differences in daily streamflow predictions by four fine-scale models and two regional-scale monthly time step models by comparing model fit statistics and bias in ecologically relevant flow statistics (ERFSs) at five sites in the Southeastern USA. Models were calibrated to different extents, including uncalibrated (level A), calibrated to a downstream site (level B), calibrated specifically for the site (level C) and calibrated for the site with adjusted precipitation and temperature inputs (level D). All models generally captured the magnitude and variability of observed streamflows at the five study sites, and increasing level of model calibration generally improved performance. All models had at least 1 of 14 ERFSs falling outside a +/−30% range of hydrologic uncertainty at every site, and ERFSs related to low flows were frequently over-predicted. Our results do not indicate that any specific hydrologic model is superior to the others evaluated at all sites and for all measures of model performance. Instead, we provide evidence that (1) model performance is as likely to be related to calibration strategy as it is to model structure and (2) simple, regional-scale models have comparable performance to the more complex, fine-scale models at a monthly time step.

Cecala, K.K. and Maerz, J.C. 2015. Context-dependent responses to light contribute to salamander responses to landscape disturbances. Canadian Journal of Zoology 94:7-13. 10.1139/cjz-2015-0111

Abstract
Behaviour often regulates population responses to environmental change, but linking behavioural responses to population patterns can be challenging because behavioural responses are often context-dependent, have an instinctive component, and yet may be modified by experience. Black-bellied salamanders (Desmognathus quadramaculatus, Holbrook 1840) occupy forested streams where dense canopies create cool, dark environments. Because riparian deforestation negatively affects salamander population connectivity yet some individuals choose to persist in these gaps, we sought to evaluate whether phototaxis could explain these patterns and whether phototactic behaviour would be influenced by experience (capture from forested or deforested areas) or context (refuge type and availability). Our results demonstrated that D. quadramaculatus larvae exhibited negative phototaxis but that larvae from forested streams exhibited stronger negative phototaxis than individuals from deforested streams. Larvae also selected habitat closer to light when refuge was available. Our results show that light alters larval D. quadramaculatus habitat use, but the magnitude of that effect depends on refuge availability and experience with well-lit conditions associated with forest removal. As human activities reduce canopy cover and refuge availability, negative phototaxis may be one explanation for behavioural barriers to movement. Ultimately, the ability of salamanders to exhibit behavioural plasticity will determine their potential for local adaptation facilitating persistence in the face of environmental change.

Chamblee, John F., Carolyn A. Dehring, Craig A. Depken II and Joseph R. Nicholson. 2015. Water Contamination, Land Prices, and the Statute of Repose. The Journal of Real Estate, Finance, and Economics. 51(3). (DOI: 10.1007/s11146-015-9514-3)

Abstract
We examine how water contamination risk from an inactive hazardous waste site is capitalized into surrounding vacant land prices. After public knowledge of the first instance of off-site contamination, we find that shallow groundwater contamination potential is negatively capitalized into land prices, as is proximity to a known contaminated well. Public knowledge of off-site contamination and associated land price changes occur after the North Carolina’s 10-year statute of repose. Our findings raise questions concerning such statutes when environmental contamination has a long latency period, especially given a recent Supreme Court ruling that Superfund law does not preempt state statutes of repose.

Craig, Metthew E.,Scott M. Pearson, Jennifer M. Fraterrigo, 2015. Grass invasion effects on forest soil carbon depend on landscape-level land use patterns. Ecology 96:2265-2279. doi: 10.1890/14-1770.1

Abstract
Plant invasions can alter the quality and quantity of detrital and root-derived inputs entering a system, thereby influencing the activities of microbial decomposers and affecting the soil carbon cycle. The effect of these inputs on soil carbon storage is often conflicting, suggesting strong context dependency in the plant–decomposer relationship. Whether there is a generalizable pattern that explains this dependency remains relatively unexplored. Here, we (1) examine how invasion by the exotic grass Microstegium vimineum affects carbon cycling across a land use gradient, and (2) evaluate the importance of inorganic nitrogen availability and other environmental variables for explaining patterns in soil carbon. Using paired invaded and uninvaded plots, we quantified invasion effects on belowground carbon pools, extracellular enzyme activities, and native leaf litter decomposition in forests embedded in an urban, agricultural, or forested landscape matrix. Compared to the urban matrix, invasion-associated declines in total soil organic carbon in the forested and agricultural landscapes were 3.5 and 2.5 times greater, respectively. Inorganic nitrogen availability and M. vimineum biomass interacted to explain these patterns: when both nitrogen availability and M. vimineum biomass were high, invaded soils exhibited higher total organic carbon, unchanged particulate organic matter carbon, and higher mineral-associated organic matter carbon compared to adjacent uninvaded soils. Consistent with these patterns, activities of carbon-mineralizing enzymes were lower in invaded than in uninvaded soils when both nitrogen availability and M. vimineum biomass were high. By contrast, decomposition of native leaf litter was faster when inorganic nitrogen availability and M. vimineum biomass were high. Our findings suggest that, although this invader may accelerate carbon cycling in forest soils, its effects on soil carbon storage largely depend on nitrogen availability and invader biomass, which can be altered by landscape-level patterns of land use. Additional research is needed to determine whether land use or other broad-scale processes such as atmospheric nitrogen deposition can explain context dependence in plant invasion effects on other ecosystem processes.

Elliott, K. J., Miniat, C. F., Pederson, N. and Laseter, S. H. (2015), Forest tree growth response to hydroclimate variability in the southern Appalachians. Glob Change Biol, 21: 4627-4641. doi:10.1111/gcb.13045

Abstract
Climate change will affect tree species growth and distribution; however, under the same climatic conditions species may differ in their response according to site conditions. We evaluated the climate-driven patterns of growth for six dominant deciduous tree species in the southern Appalachians. We categorized species into two functional groups based on their stomatal regulation and xylem architecture: isohydric, diffuse porous and anisohydric, ring porous. We hypothesized that within the same climatic regime: (i) species-specific differences in growth will be conditional on topographically mediated soil moisture availability; (ii) in extreme drought years, functional groups will have markedly different growth responses; and (iii) multiple hydroclimate variables will have direct and indirect effects on growth for each functional group. We used standardized tree-ring chronologies to examine growth of diffuse-porous (Acer, Liriodendron, and Betula) and ring-porous (Quercus) species vs. on-site climatic data from 1935 to 2003. Quercus species growing on upslope sites had higher basal area increment (BAI) than Quercus species growing on mesic, cove sites; whereas, Acer and Liriodendron had lower BAI on upslope compared to cove sites. Diffuse-porous species were more sensitive to climate than ring porous, especially during extreme drought years. Across functional groups, radial growth was more sensitive to precipitation distribution, such as small storms and dry spell length (DSL), rather than the total amount of precipitation. Based on structural equation modeling, diffuse-porous species on upslope sites were the most sensitive to multiple hydroclimate variables (r2 = 0.46), while ring-porous species on upslope sites were the least sensitive (r2 = 0.32). Spring precipitation, vapor pressure deficit, and summer storms had direct effects on summer AET/P, and summer AET/P, growing season small storms and DSL partially explained growth. Decreasing numbers of small storms and extending the days between rainfall events will result in significant growth reduction, even in regions with relatively high total annual rainfall.

Elliott, K.J., Vose, J.M., Knoepp, J.D., Clinton, B.D. and Kloeppel, B.D. 2015. Functional role of the herbaceous layer in eastern deciduous forest ecosystems. Ecosystems. 18:221-236. (DOI: 10.1007/s10021-014-9825-x)

Abstract
The importance of the herbaceous layer in regulating ecosystem processes in deciduous forests is generally unknown. We use a manipulative study in a rich, mesophytic cove forest in the southern Appalachians to test the following hypotheses: (i) the herbaceous functional group (HFG) in mesophytic coves accelerates carbon and nutrient cycling, (ii) high litter quality input and rapid nutrient turnover associated with HFG will have a positive effect on overstory tree growth, and (iii) the HFG regulates tree regeneration with negative effects on seedling establishment due to competition for resources. We established treatment plots in a mesic, cove-hardwoods forest and removed the herbaceous flora (HR, removed twice per year) or added herbaceous organic material (OMA, once per year) for comparison to a no removal (NR) reference for a total of 14 years. The OMA treatment stimulated soil N-mineralization and increased litterfall mass and N content. OMA N-mineralization rates were more than two times greater than both the NR and HR treatments; however, we did not detect significant differences in soil CO2 efflux among treatments. Higher overstory litterfall mass and N in the OMA treatment plots indicated that overstory trees were benefiting from the enhanced soil N-mineralization. Higher overstory leaf mass and N suggests an important linkage between HR and aboveground net primary production even though this did not translate into greater tree basal area increment. We found an increase in regeneration of all tree species with HFG removal, and the response was particularly evident for Acer rubrum seedlings.

Fang, Y., Sun, G., Caldwell, P., McNulty, S.G., Noormets, A., Domec, J.-C., King, J., Zhang, Z., Zhang, X., Lin, G., Zhou, G., Xiao, J. and Chen, J. 2015. Monthly land cover-specific evapotranspiration models derived from global eddy flux measurements and remote sensing data. Ecohydrology. (DOI: 10.1002/eco.1629)

Abstract
Evapotranspiration (ET) is arguably the most uncertain ecohydrologic variable for quantifying watershed water budgets. Although numerous ET and hydrological models exist, accurately predicting the effects of global change on water use and availability remains challenging because of model deficiency and/or a lack of input parameters. The objective of this study was to create a new set of monthly ET models that can better quantify landscape-level ET with readily available meteorological and biophysical information. We integrated eddy covariance flux measurements from over 200 sites, multiple year remote sensing products from the Moderate Resolution Imaging Spectroradiometer (MODIS), and statistical modelling. Through examining the key biophysical controls on ET by land cover type (i.e. shrubland, cropland, deciduous forest, evergreen forest, mixed forest, grassland, and savannas), we created unique ET regression models for each land cover type using different combinations of biophysical independent factors. Leaf area index and net radiation explained most of the variability of observed ET for shrubland, cropland, grassland, savannas, and evergreen forest ecosystems. In contrast, potential ET (PET) as estimated by the temperature-based Hamon method was most useful for estimating monthly ET for deciduous and mixed forests. The more data-demanding PET method, FAO reference ET model, had similar power as the simpler Hamon PET method for estimating actual ET. We developed three sets of monthly ET models by land cover type for different practical applications with different data availability. Our models may be used to improve water balance estimates for large basins or regions with mixed land cover types.

Ferguson, P.F., Conroy, M. and Hepinstall-Cymerman, J. 2015. Occupancy models for data with false positive and false negative errors and heterogeneity across sites and surveys. Methods in Ecology and Evolution. (DOI: 10.1111/2041-210X.12442)

Abstract
1. False positive detections, such as species misidentifications, occur in ecological data, although many models do not account for them. Consequently, these models are expected to generate biased inference. 2. The main challenge in an analysis of data with false positives is to distinguish false positive and false negative processes while modelling realistic levels of heterogeneity in occupancy and detection probabilities without restrictive assumptions about parameter spaces. 3. Building on previous attempts to account for false positive and false negative detections in occupancy models, we present hierarchical Bayesian models that utilize a subset of data with either confirmed detections of a species’ presence (CP model) or both confirmed presences and confirmed absences (CACP model). We demonstrate that our models overcome the challenges associated with false positive data by evaluating model performance in Monte Carlo simulations of a variety of scenarios. Our models also have the ability to improve inference by incorporating previous knowledge through informative priors.4. We describe an example application of the CP model to quantify the relationship between songbird occupancy and residential development, plus we provide instructions for ecologists to use the CACP and CP models in their own research.5. Monte Carlo simulation results indicated that, when data contained false positive detections, the CACP and CP models generated more accurate and precise posterior probability distributions than a model that assumed data did not have false positive errors. For the scenarios we expect to be most generally applicable, those with heterogeneity in occupancy and detection, the CACP and CP models generated essentially unbiased posterior occupancy probabilities. The CACP model with vague priors generated unbiased posterior distributions for covariate coefficients. The CP model generated unbiased posterior distributions for covariate coefficients with vague or informative priors, depending on the function relating covariates to occupancy probabilities. We conclude that the CACP and CP models generate accurate inference in situations with false positive data for which previous models were not suitable.

Ferguson, P.F., Conroy, M., Chamblee, J.F. and Hepinstall-Cymerman, J. 2015. Using structured decision making with landowners to address privateforest management and parcelization: balancing multiple objectives andincorporating uncertainty. Ecology and Society. 20 (4):27

Abstract
Parcelization and forest fragmentation are of concern for ecological, economic, and social reasons. Efforts to keep large, private forests intact may be supported by a decision-making process that incorporates landowners’ objectives and uncertainty. We used structured decision making (SDM) with owners of large, private forests in Macon County, North Carolina. Macon County has little land use regulation and a history of discordant, ineffective attempts to address land use and development. We worked with landowners to define their objectives, identify decision options for forest management, build a Bayesian decision network to predict the outcomes of decisions, and determine the optimal and least-desirable decision options. The optimal forest management options for an average, large, forested property (30 ha property with 22 ha of forest) in Macon County was crown-thinning timber harvest under the Present-Use Value program, in which enrolled property is taxed at the present-use value (growing timber for commercial harvest) rather than full market value. The least-desirable forest management actions were selling 1 ha and personal use of the forest (e.g., trails, firewood) with or without a conservation easement. Landowners reported that they enjoyed participating in the project (85%) and would reconsider what they are currently doing to manage their forest (69%). The decision that landowners initially thought would best meet their objectives did not match results from the decision network. This highlights the usefulness of SDM, which typically has been applied to decision problems involving public resources.

Hwang, T., Band, L.E., Hales, T.C., Miniat, C.F., Vose, J.M., Bolstad, P.V., Miles, B. and Price, K. 2015. Simulating vegetation controls on hurricane-induced shallow landslides with a distributed ecohydrological model. Journal of Geophysical Research: Biosciences. 120(2):361-378. (DOI: 10.1002/2014JG002824)

Abstract
The spatial distribution of shallow landslides in steep forested mountains is strongly controlled by aboveground and belowground biomass, including the distribution of root cohesion. While remote sensing of aboveground canopy properties is relatively advanced, estimating the spatial distribution of root cohesion at the forest landscape scale remains challenging. We utilize canopy height information estimated using lidar (light detecting and ranging) technology as a tool to produce a spatially distributed root cohesion model for landslide hazard prediction. We characterize spatial patterns of total belowground biomass based on the empirically derived allometric relationship developed from soil pit measurements in the Coweeta Hydrologic Laboratory, North Carolina. The vertical distribution of roots and tensile strength were sampled at soil pits allowing us to directly relate canopy height to root cohesion and use this model within a distributed ecohydrological modeling framework, providing transient estimates of runoff, subsurface flow, soil moisture, and pore pressures. We tested our model in mountainous southern Appalachian catchments that experienced a number of landslides during the 2004 hurricane season. Slope stability estimates under the assumption of spatially uniform root cohesion significantly underpredicted both the total number of landslides and the number of “false positives,” unfailed areas of the landscape that were predicted to fail. When we incorporate spatially distributed root cohesion, the accuracy of the slope stability forecast improves dramatically. With the growing availability of lidar data that can be used to infer belowground information, these methods may provide a wider utility for improving landslide hazard prediction and forecasting.

J. Bruce Wallace, Susan L. Eggert, Judy L. Meyer, and Jackson R. Webster 2015. Stream invertebrate productivity linked to forest subsidies: 37 stream-years of reference and experimental data. Ecology 96:1213-1228. http://dx.doi.org/10.1890/14-1589.1

Abstract
Riparian habitats provide detrital subsidies of varying quantities and qualities to recipient ecosystems. We used long-term data from three reference streams (covering 24 stream-years) and 13-year whole-stream organic matter manipulations to investigate the influence of terrestrial detrital quantity and quality on benthic invertebrate community structure, abundance, biomass, and secondary production in rockface (RF) and mixed substrates (MS) of forested headwater streams. Using a mesh canopy covering the entire treatment stream, we examined effects of litter exclusion, small- and large-wood removal, and addition of artificial wood (PVC) and leaves of varying quality on organic matter standing crops and invertebrate community structure and function. We assessed differences in functional feeding group distribution between substrate types as influenced by organic matter manipulations and long-term patterns of predator and prey production in manipulated vs. reference years. Particulate organic matter standing crops in MS of the treatment stream declined drastically with each successive year of litter exclusion, approaching zero after three years. Monthly invertebrate biomass and annual secondary production was positively related to benthic organic matter in the MS habitats. Rockface habitats exhibited fewer changes than MS habitats across all organic matter manipulations. With leaf addition, the patterns of functional group distribution among MS and RF habitats returned to patterns seen in reference streams. Secondary production per unit organic matter standing crop was greatest for the leaf addition period, followed by the reference streams, and significantly less for the litter exclusion and wood removal periods. These data indicate that the limited organic matter remaining in the stream following litter exclusion and wood removal was more refractory than that in the reference streams, whereas the added leaf material was more labile and readily converted into invertebrate production. Predator production and total production were tightly coupled in reference and treatment streams, indicating strong relationships between predators and their prey. Results from the artificial wood addition demonstrate that physical structure alone will not restore invertebrate productivity without detrital resources from the riparian forest. Our long-term studies conducted over three decades at the ecosystem scale unequivocally show the necessity of maintaining and restoring aquatic–terrestrial linkages in forested headwater streams.

Jackson, C. R., Leigh, D. S., Scarbrough, S. L., and Chamblee, J. F. 2015. Herbaceous Versus Forested Riparian Vegetation: Narrow and Simple Versus Wide, Woody and Diverse Stream Habitat. River Res. Applic., 31: 847-857. doi: 10.1002/rra.2783.

Abstract
We investigated interactions of riparian vegetative conditions upon a suite of channel morphological variables: active channel width, variability of width within a reach, large wood frequency, mesoscale habitat distributions, mesoscale habitat diversity, median particle size and per cent fines. We surveyed 49 wadeable streams, 45 with low levels of development, throughout the Upper Little Tennessee River Basin in the Southern Appalachians. Conversion of riparian forest to grass has reduced aquatic habitat area (quantified by active channel width), channel width variability, wood frequency, mesoscale habitat diversity and obstruction habitat (wood and rock jams), and such conversion has increased the fraction of run and glide habitat. Channels with grassy riparian zones were only one-third to three-fifths of the width of channels with forested riparian zones, and channels with grassy or narrow forested riparian zones were nearly devoid of wood. Particle size metrics were strongly affected by stream power and agricultural cover in the basin, but the data suggest that elimination of riparian forest reduces median bed particle size. Results indicate that even modest increases in the extent and width of forested riparian buffers would improve stream habitat conditions.

John S. Kominoski, Amy D. Rosemond, Jonathan P. Benstead, Vladislav Gulis, John C. Maerz, and David W. P. Manning 2015. Low-to-moderate nitrogen and phosphorus concentrations accelerate microbially driven litter breakdown rates. Ecological Applications 25:856-865. http://dx.doi.org/10.1890/14-1113.1

Abstract
Particulate organic matter (POM) processing is an important driver of aquatic ecosystem productivity that is sensitive to nutrient enrichment and drives ecosystem carbon (C) loss. Although studies of single concentrations of nitrogen (N) or phosphorus (P) have shown effects at relatively low concentrations, responses of litter breakdown rates along gradients of low-to-moderate N and P concentrations are needed to establish likely interdependent effects of dual N and P enrichment on baseline activity in stream ecosystems. We established 25 combinations of dissolved inorganic N (DIN; 55–545 lg/L) and soluble reactive P (SRP; 4–86 lg/L) concentrations with corresponding N:P molar ratios of 2–127 in experimental stream channels. We excluded macroinvertebrates, focusing on microbially driven breakdown of maple (Acer rubrum L.) and rhododendron (Rhododendron maximum L.) leaf litter. Breakdown rates, k, per day (d1) and per degree-day (dd1), increased by up to 63for maple and 123for rhododendron over our N and P enrichment gradient compared to rates at low ambient N and P concentrations. The best models of k (d1 and dd1) included litter species identity and N and P concentrations; there was evidence for both additive and interactive effects of N and P. Models explaining variation in k dd1 were supported by N and P for both maple and rhododendron (R2 adj ¼0.67 and 0.33, respectively). Residuals in the relationship between k dd1 and N concentration were largely explained by P, but residuals for k dd1 and P concentration were less adequately explained by N. Breakdown rates were more closely related to nutrient concentrations than variables associated with measurements of two mechanistic parameters associated with C loss (fungal biomass and microbial respiration rate). We also determined the effects of nutrient addition on litter C: nutrient stoichiometry and found reductions in litter C:N and C:P along our experimental nutrient gradient. Our results indicate that microbially driven litter processing rates increase across low-to-moderate nutrient gradients that are now common throughout human-modified landscapes.

Knoepp, Jennifer D.; Taylor, R. Scott; Boring, Lindsay R.; Miniat, Chelcy F., 2015, Influence of Forest Disturbance on Stable Nitrogen Isotope Ratios in Soil and Vegetation Profiles, Soil Science Society of America Journal, 79:1470-1481, doi:10.2136/sssaj2015.03.0101

Abstract
Soil and plant stable N isotope ratios (d15N) are influenced by atmospheric N2 inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting d15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems, longleaf pine (Pinus palustris Mill.)–wiregrass (Aristida stricta Michx.) (LLP) and Appalachian hardwood (AHW) forests in the US Southeast under different management regimes. In LLP, burning removes OM. In AHW, clearcutting creates large OM pulses of logging residue. Although burning removes OM and clearcutting creates a pulse addition of OM, both management regimes increase soil N availability 0and N 2–fixing plants. The LLP treatments included burning every 2 yr with N2 fixers and reference fire exclusion sites without N 2 fixers. The AHW included 25-yr-old clearcut plots with and without N2 fixers, and uncut reference without N 2 fixers. We hypothesized that: (i) compared with the reference, OM removal (LLP) would enrich d15N values while OM addition (AHW) would deplete d15N in soil and vegetation pools; and (ii) N2 fixers would mitigate d15N enrichment in LLP response and exacerbate d15N depletion in AHW. We examined total d15N in soil profiles, tree increment cores, and foliage. The LLP soil and vegetation d15N values showed no treatment effect. In AHW, d15N values in clearcut subsurface soils (20–60 cm) were lower than the reference, but N 2 fixers had no effect. Wood d15N differed with treatment; N2 fixers had no effect. Our data suggest that AHW soil profile d15N patterns may indicate past disturbance; however, wood and foliar d15N response is species specific. Additionally, N2–fixing plants respond to ecosystem disturbance, but the data suggest that they play little role in soil or plant d15N values.

Leigh, D.S., Gragson, T. and Coughlan, M. 2015. Pedogenic effects of mid- to late-Holocene conversion of forests to pastures in the French western Pyrenees. Zeitschrift für Geomorphologie. 59:225-245.

Abstract
This paper presents a place-based examination of the timing and long-term pedogenic effects of human-induced forest to pasture conversion in the French western Pyrenees Mountains, Basque commune of Larrau. We analyzed colluvial stratigraphic sections to derive the chronology of landscape change using radiocarbon dating, charcoal concentrations, magnetic susceptibility, and n-alkanes to reveal when forests were replaced by pastures (largely by intentional use of fire). In addition, we compared properties of native forest soils to those of adjacent long-term pastures using a paired t-test approach. Results indicate that intense burning and clearing occurred in the late Holocene, starting at about 4,000 cal yr BP, but limited fires occurred on the landscape during the early and middle Holocene. After 4,000 cal yr BP the sedimentation rates significantly increased, constituting “legacy” sediment, but post-4,000 cal yr BP sedimentation rates remain well within a range typical for forested hillsides (< 1 mm yr-1). Thus, erosional degradation is not apparent. Our paired analysis of old-growth forests compared to long-term pastures reveals that soils of millennial pastures are building up by additions of organic matter and phytoliths, as well as by decreases in bulk density of topsoils. The pastured A horizons are triple the thickness of those in forests, and pastures have significantly lower bulk densities, resulting in much more rapid water infiltration capacities. Although the concentrations of some inorganic nutrients in the pastured soils are significantly lower than in forested soils (mg kg-1 basis), the overall result is that the soils in pastures are of higher quality than those in forests. Melanization of the pastured profiles is an indirect anthropogenic process that has built-up the A horizons through time, which testifies to the importance of human agency in long-term soil evolution. The agropastoral uplands of Larrau stand in contrast to conventional degradation narratives of millennially grazed landscapes. The apparent sustainability of this landscape suggests that over the long term, agropastoral land use actually can result in changes to soils and landscapes that facilitate conservation.

Leigh, David S., Theodore L. Gragson, Michael R. Coughlan. 2015. Colluvial legacies of millennial landscape change on individual hillsides, place-based investigation in the western Pyrenees Mountains, Quaternary International. DOI:10.1016/j.quaint.2015.08.031

Abstract
We detect transition to agropastoral land use in a mountain landscape by radiocarbon dating physical signatures (sedimentation rates, charcoal concentrations, magnetic susceptibility) of conversion from native forest to pasture contained within colluvial stratigraphic sections. Focus is on two study sites located on toeslopes directly beneath zero-order hollows draining several hectares in the commune of Larrau (Pyrénées Atlantiques, France) along the international drainage divide of the western Pyrenees. Sample sites maximize likelihood of spatially and temporally uniform slopewash sedimentation. This constitutes a place-based approach to decipher the chronology of agropastoral activities within individual fields, which is applicable to other mountain ranges of the world. Stratigraphic columns were augured in contiguous 10 cm sample levels, which produced temporal resolution of decades to several centuries. We interpret relatively high concentrations of charcoal, rapid sedimentation, and magnetic susceptibility patterns as evidence of the intentional use of fire to transform forests into pastures. Results indicate that intentional burning and clearing probably were initiated by the Late Neolithic (ca. 5000–6000 cal. BP). However, intense burning, extensive forest clearance, and erosional degradation occurred later during the Bronze Age at one site, and during the Iron Age at the other site. This non-synchronous pattern of charcoal abundance and sedimentation rates is consistent with human agency of land clearance driving the chronology rather than paleoclimatic drivers. Stratigraphic zones of rapid sedimentation at both sites constitute “legacy” sediment of great antiquity. Our results are consistent with similar shifts in fire regimes and vegetation assemblages derived from direct association with anthropogenic proxies (e.g. pastoral pollen taxa, fungal spores of sheep dung, and archaeological sites) elsewhere in the Pyrenees and other European mountains. Consequently, our method may provide a good indicator of human presence and land-use activities for mountainous areas where paleoenvironmental records from bogs, lakes, and archaeological sites are limited.

Lin, L., J. R. Webster, T. Hwang, and L. E. Band 2015. Effects of lateral nitrate flux and instream processes on dissolved inorganic nitrogen export in a forested catchment: A model sensitivity analysis, Water Resour. Res., 51, 2680-2695, (doi:10.1002/2014WR015962).

Abstract
The importance of terrestrial and aquatic ecosystems in controlling nitrogen dynamics in streams is a key interest of ecologists studying dissolved inorganic nitrogen (DIN) export from watersheds. In this study, we coupled a stream model with a terrestrial ecohydrological model and conducted a global sensitivity analysis to evaluate the relative importance of both ecosystems to nitrogen export. We constructed two scenarios (‘‘normal’’ and high nitrate loads) to explore conditions under which terrestrial (lateral nitrate flux) or aquatic ecosystems (instream nutrient processes) may be more important in controlling DIN export. In a forest catchment, although the forest ecosystem controls the nitrogen load to streams, sensitivity results suggested that most nitrogen output from the terrestrial ecosystem was taken up by instream microbial immobilization associated with benthic detritus and retained in detritus. Later the immobilized nitrogen was remineralized as DIN. Therefore, the intra-annual pattern of DIN concentration in the stream was low in fall and became high in spring. Not only was instream microbial immobilization saturated with the high nitrogen load scenario, but also the net effect of immobilization and mineralization on DIN export was minimized because nitrogen cycling between organic and inorganic forms was accelerated. Overall, our linked terrestrial-aquatic model simulations demonstrated that stream process could significantly affect the amount and timing of watershed nitrogen export when nitrogen export from the terrestrial system is low. However, when nitrogen export from the terrestrial system is high, the effect of stream processes is minimal.

Manning, David W. P., Amy D.Rosemond, John S. Kominoski, Vladislav Gulis, Jonathan P. Benstead and John C. Maerz, 2015, Detrital stoichiometry as a critical nexus for the effects of streamwater nutrients on leaf litter breakdown rates, Ecology, 86, 8, pp 2214-2224, doi: 10.1890/14-1582.1

Abstract
Nitrogen (N) and phosphorus (P) concentrations are elevated in many freshwater systems, stimulating breakdown rates of terrestrially derived plant litter; however, the relative importance of N and P in driving litter breakdown via microbial and detritivore processing are not fully understood. Here, we determined breakdown rates of two litter species, Acer rubrum (maple) and Rhododendron maximum (rhododendron), before (PRE) and during two years (YR1, YR2) of experimental N and P additions to five streams, and quantified the relative importance of hypothesized factors contributing to breakdown. Treatment streams received a gradient of P additions (low to high soluble reactive phosphorus [SRP]; ;10–85 lg/L) crossed with a gradient of N additions (high to low dissolved inorganic nitrogen [DIN]; ;472–96 lg/L) to achieve target molar N:P ratios ranging from 128 to 2. Litter breakdown rates increased above pre-treatment levels by an average of 1.1–2.23 for maple, and 2.7–4.93 for rhododendron in YR1 and YR2. We used path analysis to compare fungal biomass, shredder biomass, litter stoichiometry (nutrient content as C:N or C:P), discharge, and streamwater temperature as predictors of breakdown rates and compared models containing streamwater N, P or N þ P and litter C:N or C:P using model selection criteria. Litter breakdown rates were predicted equally with either streamwater N or P (R2 ¼ 0.57). In models with N or P, fungal biomass, litter stoichiometry, discharge, and shredder biomass predicted breakdown rates; litter stoichiometry and fungal biomass were most important for model fit. However, N and P effects may have occurred via subtly different pathways. Litter N content increased with fungal biomass (N-driven effects) and litter P content increased with streamwater P availability (P-driven effects), presumably via P storage in fungal biomass. In either case, the effects of N and P through these pathways were associated with higher shredder biomass and breakdown rates. Our results suggest that N and P stimulate litter breakdown rates via mechanisms in which litter stoichiometry is an important nexus for associated microbial and detritivore effects.

Milanovich, J.R., Maerz, J.C. and Rosemond, A.D. 2015. Stoichiometry and estimates of nutrient standing stocks of larval salamanders in Appalachian headwater streams. Freshwater Biology. (DOI: 10.1111/fwb.12572)

Abstract
1. Because of their longevity and skeletal phosphorus demand, vertebrates can have distinct influences on the uptake, storage and recycling of nutrients in ecosystems. Quantification of body stoichiometry, combined with estimates of abundance or biomass, can provide insights into the effect of vertebrates on nutrient cycling.2. We measured the nutrient content and estimated the abundance and biomass of the larvae of three salamander species to characterise the factors that influence larval salamander stoichiometry and estimate the contribution of larval salamanders to nutrient standing stock and recycling in five southern Appalachian headwaters.3. The proportion and ratios of carbon (C), nitrogen (N), phosphorus (P) and calcium (Ca) in larval salamanders varied with size within and among species. We found negative relationships between body size and whole-body %N, C : P and N : P and positive relationships between body size and whole-body %P and C : N. Mean estimated larval salamander density was 58 m−2 and mean estimated dry biomass was 2813 mg m−2. Estimated standing stock of N, P and Ca were 332, 81 and 103 mg m−2, respectively, which was 1.1 × and 4.6 × greater than estimated amounts of N and P reported for macroinvertebrate taxa in similar streams within the region and was higher than in many other consumers in freshwater habitats. Using data from previous studies, we estimate that the mean ingestion rate of N and P by plethodontids is 0.000001 and 0.00001 g−1 day−1, respectively, while excretion rates of both are <0.00001 g day−1.4. Salamanders are the only abundant vertebrates within headwater Appalachian streams, and our results show that larval salamanders represent a large standing stock of N, P and Ca in these streams. These findings complement other recent research demonstrating the effects of larval stream salamanders on macroinvertebrate abundance and seasonal nutrient supply in Appalachian headwaters and stress the importance of plethodontid salamanders to headwater stream processes.

Norman, J. S., L. Lin, and J. E. Barrett. 2015. Paired carbon and nitrogen metabolism by ammonia-oxidizing bacteria and archaea in temperate forest soils. Ecosphere 6(10):176. http://dx.doi.org/10.1890/ES14-00299.1

Abstract
Nitrification is a biologically mediated nutrient transformation, which influences the availability of inorganic nitrogen to other microorganisms and plants and mediates mobility of nitrogen in the environment. Ammonia oxidation, the rate-limiting step of nitrification, is performed by two groups of microbes: ammonia-oxidizing archaea (AOA) and bacteria (AOB) that couple this process with the chemoautotrophic fixation of carbon. Due to the energetic constraints on these organisms, both AOA and AOB likely oxidize large amounts of ammonia to fix relatively small amounts of carbon in natural environments. Here we sought to investigate paired carbon and nitrogen metabolism by AOA and AOB in forest soils. To accomplish this objective, we used quantitative polymerase chain reaction (qPCR) to quantify changes in AOA and AOB ammonia monooxygenase subunit A (amoA) genes during in situ incubations. We then used qPCR data alongside AOA and AOB community profiles at each site to convert changes in amoA gene copy number to carbon accumulation by each group. Finally, we regressed group-specific carbon accumulation values against observed values of NO3-accumulation to establish cross-site relationships between ammonia oxidation and carbon accumulation by each group. By this procedure we estimated that forest soil AOA oxidized 59.8 µg of ammonia-N to add 1 µg of carbon to biomass, while forest soil AOB oxidized 58.2 µg of ammonia-N to add 1 µg of carbon to biomass. These findings represent the first field-based estimates of paired carbon and nitrogen metabolism by these organisms, and could be used to inform microbially explicit models of nitrification in forest soils.

Novick, K.A., Oishi, A.C., Ward, E.J., Siqueira, M.B., Juang, J.-Y. and Stoy, P.C. 2015. On the difference in the net ecosystem exchange of CO2 between deciduous and evergreen forests in the southeastern United States. Global Change Biology. 21(2):827-842. (DOI: doi 10.1111/gcb.12723)

Abstract
The southeastern United States is experiencing a rapid regional increase in the ratio of pine to deciduous forest ecosystems at the same time it is experiencing changes in climate. This study is focused on exploring how these shifts will affect the carbon sink capacity of southeastern US forests, which we show here are among the strongest carbon sinks in the continental United States. Using eight-year-long eddy covariance records collected above a hardwood deciduous forest (HW) and a pine plantation (PP) co-located in North Carolina, USA, we show that the net ecosystem exchange of CO2 (NEE) was more variable in PP, contributing to variability in the difference in NEE between the two sites (ΔNEE) at a range of timescales, including the interannual timescale. Because the variability in evapotranspiration (ET) was nearly identical across the two sites over a range of timescales, the factors that determined the variability in ΔNEE were dominated by those that tend to decouple NEE from ET. One such factor was water use efficiency, which changed dramatically in response to drought and also tended to increase monotonically in nondrought years (P < 0.001 in PP). Factors that vary over seasonal timescales were strong determinants of the NEE in the HW site; however, seasonality was less important in the PP site, where significant amounts of carbon were assimilated outside of the active season, representing an important advantage of evergreen trees in warm, temperate climates. Additional variability in the fluxes at long-time scales may be attributable to slowly evolving factors, including canopy structure and increases in dormant season air temperature. Taken together, study results suggest that the carbon sink in the southeastern United States may become more variable in the future, owing to a predicted increase in drought frequency and an increase in the fractional cover of southern pines.

Phillip M. Bumpers, John C. Maerz, Amy D. Rosemond, and Jonathan P. Benstead 2015. Salamander growth rates increase along an experimental stream phosphorus gradient. Ecology 96:2994-3004. http://dx.doi.org/10.1890/14-1772.1

Abstract
Nutrient-driven perturbations to the resource base of food webs are predicted to attenuate with trophic distance, so it is unclear whether higher-level consumers will generally respond to anthropogenic nutrient loading. Few studies have tested whether nutrient (specifically, nitrogen [N] and phosphorus [P]) enrichment of aquatic ecosystems propagates through multiple trophic levels to affect predators, or whether N vs. P is relatively more important in driving effects on food webs. We conducted two-year whole-stream N and P additions to five streams to generate gradients in N and P concentration and N:P ratio (target N:P = 2, 8, 16, 32, 128). Larval salamanders are vertebrate predators of primary and secondary macroinvertebrate consumers in many heterotrophic headwater streams in which the basal resources are detritus and associated microorganisms. We determined the effects of N and P on the growth rates of caged and free-roaming larval Desmognathus quadramaculatus and the average body size of larval Eurycea wilderae. Growth rates and average body size increased by up to 40% and 60%, respectively, with P concentration and were negatively related to N:P ratio. These findings were consistent across both species of salamanders using different methodologies (cage vs. free-roaming) and at different temporal scales (3 months vs. 2 yr). Nitrogen concentration was not significantly related to increased growth rate or body size of the salamander species tested. Our findings suggest that salamander growth responds to the relaxation of ecosystem-level P limitation and that moderate P enrichment can have relatively large effects on vertebrate predators in detritus-based food webs.

Rice, J.L., Burke, B.J. and Heynen, N. 2015. Knowing climate change, embodying climate praxis: experimential knowledge in southern Appalachia. Annals of the Association of American Geographers. 105(2):253-262. (DOI: 10.1080/00045608.2014.985628)

Abstract
Whether used to support or impede action, scientific knowledge is now, more than ever, the primary framework for political discourse on climate change. As a consequence, science has become a hegemonic way of knowing climate change by mainstream climate politics, which not only limits the actors and actions deemed legitimate in climate politics but also silences vulnerable communities and reinforces historical patterns of cultural and political marginalization. To combat this “post-political” condition, we seek to democratize climate knowledge and imagine the possibilities of climate praxis through an engagement with Gramscian political ecology and feminist science studies. This framework emphasizes how antihierarchical and experiential forms of knowledge can work to destabilize technocratic modes of governing. We illustrate the potential of our approach through ethnographic research with people in southern Appalachia whose knowledge of climate change is based in the perceptible effects of weather, landscape change due to exurbanization, and the potential impacts of new migrants they call “climate refugees.” Valuing this knowledge builds more diverse communities of action, resists the extraction of climate change from its complex society–nature entanglements, and reveals the intimate connections between climate justice and distinct cultural lifeways. We argue that only by opening up these new forms of climate praxis, which allow people to take action using the knowledge they already have, can more just socioecological transformations be brought into being.

Rice, Jennifer L.; Burke, Brian J.; Heynen, Nik 2015. Knowing climate change, embodying climate praxis: experiential knowledge in southern Appalachia. Annals of the Association of American Geographers. 105(2): 253-262. 11 p. http://dx.doi.org/10.1080/00045608.2014.985628

Abstract
Whether used to support or impede action, scientific knowledge is now, more than ever, the primary framework for political discourse on climate change. As a consequence, science has become a hegemonic way of knowing climate change by mainstream climate politics, which not only limits the actors and actions deemed legitimate in climate politics but also silences vulnerable communities and reinforces historical patterns of cultural and political marginalization. To combat this “post-political” condition, we seek to democratize climate knowledge and imagine the possibilities of climate praxis through an engagement with Gramscian political ecology and feminist science studies. This framework emphasizes how antihierarchical and experiential forms of knowledge can work to destabilize technocratic modes of governing. We illustrate the potential of our approach through ethnographic research with people in southern Appalachia whose knowledge of climate change is based in the perceptible effects of weather, landscape change due to exurbanization, and the potential impacts of new migrants they call “climate refugees.” Valuing this knowledge builds more diverse communities of action, resists the extraction of climate change from its complex society–nature entanglements, and reveals the intimate connections between climate justice and distinct cultural lifeways. We argue that only by opening up these new forms of climate praxis, which allow people to take action using the knowledge they already have, can more just socioecological transformations be brought into being.

Schliep, Erin M., Alan E. Gelfand, James S, Clark and Kai Zhu, 2015, Modeling change in forest biomass across the eastern US, Environmental and Ecological Statistics, pp 1-19,10.1007/s10651-015-0321-z

Abstract
Predictions of above-ground biomass and the change in above-ground biomassrequireattachmentofuncertaintyduetherangeofreportedpredictionsforforests. Because above-ground biomass is seldom measured, there have been no opportunities to obtain such uncertainty estimates. Standard methods involve applying an allometric equation to each individual tree on sample plots and summing the individual values. There is uncertainty in the allometry which leads to uncertainty in biomass at the tree level. Due to interdependence between competing trees, the uncertainty at the plot level that results from aggregating individual tree biomass in this way is expected to overestimate variability. That is, the variance at the plot level should be less than the sum of the individual variances. We offer a modeling strategy to learn about change in biomass at the plot level and model cumulative uncertainty to accommodate this dependence among neighboring trees. The plot-level variance is modeled using a parametric density-dependent asymptotic function. Plot-by-time covariate information is introduced to explain the change in biomass. These features are incorporated into a hierarchical model and inference is obtain within a Bayesian framework. We analyze data for the eastern United States from the Forest Inventory and Analysis (FIA) Program of the US Forest Service. This region contains roughly 25,000 FIA monitored plots from which there are measurements of approximately 1 million trees spanning more than 200 tree species. Due to the high species richness in the FIA data, we combine species into plant functional types. We present predictions of biomass and change in biomass for two plant functional types.

Schwalm, C., Huntzinger, D., Cook, R., Wei, Y., Baker, I., Neilson, R., Poulter, B., Caldwell, P., Sun, G., Tian, H. and Zeng, N. 2015. How well do terrestrial biosphere models simulate coarse-scale runoff in the contiguous United States? Ecological Modelling. 303:87-96. (DOI: http://dx.doi.org/10.1016/j.ecolmodel.2015.02.006.)

Abstract
Significant changes in the water cycle are expected under current global environmental change. Robust assessment of present-day water cycle dynamics at continental to global scales is confounded by shortcomings in the observed record. Modeled assessments also yield conflicting results which are linked to differences in model structure and simulation protocol. Here we compare simulated gridded (1° spatial resolution) runoff from six terrestrial biosphere models (TBMs), seven reanalysis products, and one gridded surface station product in the contiguous United States (CONUS) from 2001 to 2005. We evaluate the consistency of these 14 estimates with stream gauge data, both as depleted flow and corrected for net withdrawals (2005 only), at the CONUS and water resource region scale, as well as examining similarity across TBMs and reanalysis products at the grid cell scale. Mean runoff across all simulated products and regions varies widely (range: 71 to 356 mm yr−1) relative to observed continental-scale runoff (209 or 280 mm yr−1 when corrected for net withdrawals). Across all 14 products 8 exhibit Nash–Sutcliffe efficiency values in excess of 0.8 and three are within 10% of the observed value. Region-level mismatch exhibits a weak pattern of overestimation in western and underestimation in eastern regions—although two products are systematically biased across all regions—and largely scales with water use. Although gridded composite TBM and reanalysis runoff show some regional similarities, individual product values are highly variable. At the coarse scales used here we find that progress in better constraining simulated runoff requires standardized forcing data and the explicit incorporation of human effects (e.g., water withdrawals by source, fire, and land use change).

Smith, M., et al. (2015). Global environmental change and the nature of aboveground net primary productivity responses: insights from long-term experiments. Oecologia 177(4): 935-947.

Abstract
Many global change drivers chronically alter resource availability in terrestrial ecosystems. Such resource alterations are known to affect aboveground net primary production (ANPP) in the short term; however, it is unknown if patterns of response change through time. We examined the magnitude, direction, and pattern of ANPP responses to a wide range of global change drivers by compiling 73 datasets from long-term (>5 years) experiments that varied by ecosystem type, length of manipulation, and the type of manipulation. Chronic resource alterations resulted in a significant change in ANPP irrespective of ecosystem type, the length of the experiment, and the resource manipulated. However, the pattern of ecosystem response over time varied with ecosystem type and manipulation length. Continuous directional responses were the most common pattern observed in herbaceous-dominated ecosystems. Continuous directional responses also were frequently observed in longer-term experiments (>11 years) and were, in some cases, accompanied by large shifts in community composition. In contrast, stepped responses were common in forests and other ecosystems (salt marshes and dry valleys) and with nutrient manipulations. Our results suggest that the response of ANPP to chronic resource manipulations can be quite variable; however, responses persist once they occur, as few transient responses were observed. Shifts in plant community composition over time could be important determinants of patterns of terrestrial ecosystem sensitivity, but comparative, long-term studies are required to understand how and why ecosystems differ in their sensitivity to chronic resource alterations.

Steere, Benjamin A. Revisiting platform mounds and townhouses in the Cherokee heartland: A collaborative approach. Southeastern Archaeology 2015; 34(3), 196-219. DOI: 10.1179/2168472315Y.0000000001

Abstract
This article describes the development and initial results of the Western North Carolina Mounds and Towns Project, a collaborative endeavor initiated by the Tribal Historic Preservation Office of the Eastern Band of Cherokee and the Coweeta Long Term Ecological Research Program at the University of Georgia. The goal of this project is to generate new information about the distribution of late prehistoric mounds and historic period townhouses in western North Carolina. This ongoing research has produced updated location and chronological data for 15 Mississippian period mounds and historic Cherokee townhouses, and led to the discovery of a possible location for the Jasper Allen mound. Using these new data, I suggest that David Hally's model for the territorial size of Mississippian polities provides a useful framework for generating new research questions about social and political change in western North Carolina. I also posit that the cultural practice of rebuilding townhouses in place and on top of Mississippian period platform mounds, a process that Christopher Rodning describes as “emplacement,” was common across western North Carolina. In terms of broader impacts, this project contributes positively to the development of indigenous archaeology in the Cherokee heartland.

Sun, G., Caldwell, P.V. and McNulty, S.G. 2015. Modelling the potential role of forest thinning in maintaining water supplies under a changing climate across the conterminous United States. Hydrological Processes. (DOI: 10.1002/hyp.10469) (accepted)

Abstract
The goal of this study was to test the sensitivity of water yield to forest thinning and other forest management/disturbances and climate across the conterminous United States (CONUS). Leaf area index (LAI) was selected as a key parameter linking changes in forest ecosystem structure and functions. We used the Water Supply Stress Index model to examine water yield response under 18 scenarios that combine hypothetical LAI changes (+10%, ±20%, −50%, and −80%), uniform increases in temperature (+1 °C and +2 °C) and precipitation change (±10%), and four climate change scenarios projected by general circulation models (GCMs) for the year 2050. Approximately 2100 large basins produced approximately 2003 billion cubic metres of water annually from 2002 to 2007. Forest lands covered 23% of the land surface area, but contributed 43% of the total water yield for the CONUS. As a whole, water yield increased by 3%, 8%, and 13% when LAI was reduced 20%, 50%, and 80%, respectively, while water yield decreased by 3% when LAI increased by 20%. Temperature increases of 2 °C alone could decrease water yield by 11%. A reduction of precipitation by 10% and 20% could result in a decrease of water yield by 20% and 39%, respectively. The direction and magnitude of water yield response to the combinations of LAI (+10%), climate warming (+1 °C), and precipitation change (±10%) were dominated by the change in precipitation. Climate change projected by the four GCMs (CSIROMK2 B2, CSIROMK3.5 A1B, HADCM3 B2, and MIROC32 A1B) resulted in a large change in water yield (+18% to −64%) by 2045–2055 when compared with the baseline. A 50% reduction in forest LAI under the four GCMs scenarios could greatly mitigate or exacerbate future climate change impacts on water yield in forest-dominated watersheds with high precipitation. This study provides the first quantitative estimate of the effects of forest thinning options on water yield under future climate across the CONUS. Effective forest water management for climate mitigation should focus on those watersheds identified. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Wang, Lixin and Leigh, David S. 2015. Anthropic signatures in alluvium of the Upper Little Tennessee River valley, Southern Blue Ridge Mountains, USA. Anthropocene. 11:35-47. doi:10.1016/j.ancene.2015.11.005.

Abstract
Human activities have become important influences on the fluvial system since the postColonial settlement of eastern North America. This research aims to identify post-settlement anthropic signatures in alluvial sediments in the Upper Little Tennessee River valley within the Southern Blue Ridge Mountains, USA, a relatively remote region where agricultural and mining activities were scattered and discontinuous. We compared the physical and chemical characteristics of sediments in post-settlement and pre-settlement stratigraphic units at three separate sites. Chronologies were calculated using non-linear power functions based on radiocarbon, optically stimulated luminescence ages, as well as dates from 137Cs techniques and historic records, which suggest sedimentation rates increased with time during the postsettlement period but decreased with time during the pre-settlement period. In addition, longterm average sedimentation rates are one order-of-magnitude higher in the post-settlement time than in the pre-settlement time. Sediment becomes finer upward through the pre-settlement unit but coarsens-upward in the post-settlement unit. Statistical analyses on adsorbed elemental concentrations suggest that three elements (Ca, Hg, Pb) clearly differentiate sediments between pre-settlement and post-settlement periods. The identified anthropic signatures thus include higher sedimentation rates, coarser sediment texture, and higher concentrations of the three elements in the post-settlement units. These probably relate to human activities such as intensive commercial timber harvest and scattered gold mining in the late 19th and early 20th century, modern agricultural practices, and urbanization since the 1970s. Our findings demonstrate significant impact on fluvial systems in regions with very limited history of intense human activities that stand in stark contrast to other parts of the world like Europe and Asia that record thousands of years of anthropic impact.

Warren, R. J., II, S. M. Pearson, S. Henry, K. Rossouw, J. P. Love, M. J. Olejniczak, K. J. Elliott, and M. A. Bradford. 2015. Cryptic indirect effects of exurban edges on a woodland community. Ecosphere 6(11):218. http://dx.doi.org/10.1890/ES15-00318.1

Abstract
Exurban development (e.g., second homes) in woodlands spreads urban land use impactsbeyond suburbs, but because exurban developments often retain many components of original ecosystemstructure—such as a forest canopy rather than open lawn—their ecological impacts may beunderestimated. Changes in seed-dispersing ant behavior prompted by exurban land use, such as edgeavoidance, may pose deleterious impacts on the woodland plants (myrmecochores) they disperse, andhence the floristic diversity of exurban forests. We examined the effects of exurbanization on seeddispersingant nesting and foraging, seed retrieval, dispersal direction and subsequent impact onmyrmecochores. We used a matrix of forested and exurbanized habitats to test whether (1) exurban edgesdecrease ant nest colonization and seed foraging, (2) ants disperse seeds away from exurban edges, and (3)consequently, there is lower ant-dispersed plant abundance nearer exurban edges. We found that exurbandevelopment poses little impact on keystone seed-dispersing ants because they foraged, colonized andthrived in fragmented woodland habitats as well as they did in intact forests. Exurban edges changed antbehavior, however, so that they generally moved seeds toward forest interiors, and, hence, away fromedges. Corresponding to this behavioral change, we found that ant-dispersed plants declined withproximity to edges, whereas other woodland herbs with dispersal modes other than ants were unaffected.Exurbanization poses little threat to seed-dispersing ant viability, but, by changing foraging patterns(specifically, limiting the directionality of dispersal), it indirectly threatens the plants they disperse. Edgeeffects on biota commonly are associated with cascades through abiotic resources, but we show adeleterious biotic cascade between exurban edge, keystone ants and herbaceous plants. Species-mediatedservices, such as seed dispersal and pollination, are key resources, and assessing the full consequences ofland use change therefore necessitates evaluation of impacts on biotic interactions.

Wyderko, Jennie A., Benfield, Ernest F., Maerz, John C., Cecala, Kristen K., Belden, Lisa K. (2015) Variable infection of stream salamanders in the southern Appalachians by the trematode Metagonimoides oregonensis (family: Heterophyidae). Parasitol Research, 114:3159-3165. DOI 10.1007/s00436-015-4550-8

Abstract
Many factors contribute to parasites varying in host specificity and distribution among potential hosts. Metagonimoides oregonensis is a digenetic trematode that uses stream-dwelling plethodontid salamanders as second intermediate hosts in the Eastern US. We completed a field survey to identify which stream salamander species, at a regional level, are most likely to be important for transmission to raccoon definitive hosts. We surveyed six plethodontid species (N=289 salamanders) from 23 Appalachian headwater sites in North Carolina: Desmognathus quadramaculatus (n=69), Eurycea wilderae (n=160), Desmognathus ocoee (n=31), Desmognathus monticola (n=3), Eurycea guttolineata (n=7), and Gyrinophilus porphyriticus (n=19). We found infection in all species except D. monticola. Further analysis focused on comparing infection in the two most abundant species, D. quadramaculatus and E. wilderae. We found that D. quadramaculatus had significantly higher infection prevalence and intensity, probably due to a longer aquatic larval period and larger body sizes and thus greater cumulative exposure to the parasite.

Zhu, K., C. Woodall, and J.S. Clark. 2015. Prevalence and strength of density-dependent tree recruitment, Ecology 96(9):2319-2327.

Abstract
Density dependence could maintain diversity in forests, but studies continue to disagree on its role. Part of the disagreement results from the fact that different studies have evaluated different responses (survival, recruitment, or growth) of different stages (seeds, seedlings, or adults) to different inputs (density of seedlings, density or distance to adults). Most studies are conducted on a single site and thus are difficult to generalize. Using USDA Forest Service’s Forest Inventory and Analysis data, we analyzed over a million seedling-tosapling recruitment observations of 50 species from the eastern United States, controlling for the effects of climate. We focused on the per-seedling recruitment rate, because it is most likely to promote diversity and to be identified in observational or experimental data. To understand the prevalence of density dependence, we quantified the number of species with significant positive or negative effects. To understand the strength of density dependence, we determined the magnitude of effects among con- and heterospecifics, and how it changes with overall species abundance. We found that density dependence is pervasive among the 50 species, as the majority of them have significant effects and mostly negative. Density-dependence effects are stronger from conspecific than heterospecfic adult neighbors, consistent with the predictions of the Janzen-Connell hypothesis. Contrary to recent reports, density-dependence effects are more negative for common than rare species, suggesting disproportionately stronger population regulation in common species. We conclude that density dependence is pervasive, and it is strongest from conspecific neighbors of common species. Our analysis provides direct evidence that density dependence regulates population dynamics of tree species in eastern U.S. forests.

Adams, M., Knoepp, J.D. and Webster, J.R. 2014. Inorganic nitrogen retention by watersheds at Fernow Experimental Forest and Coweeta Hydrologic Laboratory. Soil Science Society of America Journal. (DOI: 10.2136/sssaj2013.11.0463nafsc)

Abstract
Because elevated N loading can impair both terrestrial and aquatic ecosystems, understanding the abiotic and biotic controls over retention and export of dissolved inorganic N (DIN) is crucial. Long-term research has been conducted on experimental watersheds at two U.S. Forest Service experimental forests in the Appalachian region: Fernow Experimental Forest (FEF) in West Virginia and Coweeta Hydrologic Laboratory (CHL) in North Carolina. While similar in vegetation and research history, FEF and CHL differ in climate, historic DIN deposition, and soils. We evaluated long- term patterns of DIN inputs and exports from three watersheds at each location with similar treatments including clear-cut harvest, conversion to conifer plantation (Norway spruce [ Picea abies (L.) H. Karst.] at FEF and white pine [ Pinus strobus L.] at CHL), as well as reference watersheds. We examined DIN export and retention in these watersheds, comparing treated and reference watersheds within each experimental forest and comparing similarly treated watersheds between the experimental forests. Despite current similar levels of N deposition, stream water DIN concentrations and exports were generally greater at FEF by almost an order of magnitude. We found differences between FEF and CHL in stream DIN concentrations, watershed export, and retention of DIN inputs not only in the untreated reference watersheds but also in the watersheds with similar disturbance treatment. We hypothesize that these differences are the result of site and vegetation differences as well as site history including long-term patterns of DIN deposition. We document the switch from biogeochemical to hydrologic controls that occurred when N availability exceeded N immobilization, due to either N deposition or biological N inputs.

Band, L. E., McDonnell, J. J., Duncan, J. M., Barros, A., Bejan, A., Burt, T., Dietrich, W. E., Emanuel, R. E., Hwang, T., Katul, G., Kim, Y., McGlynn, B., Miles, B., Porporato, A., Scaife, C. and Troch, P. A. (2014), Ecohydrological flow networks in the subsurface. Ecohydrol., 7: 1073–1078. doi:10.1002/eco.1525

Abstract
Preferential flow in hillslope systems through subsurface networks developed from a range of botanical, faunal and geophysical processes have been observed and inferred for decades and may provide a large component of the bulk transport of water and solutes. However, our dominant paradigm for understanding and modelling hillslope hydrologic processes is still based on the Darcy–Richards matric flow framework, now with a set of additional methods to attempt to reproduce some of the aggregate function of the two-phase system of network and matrix flow. We call for a community effort to design and implement a set of well planned experiments in different natural and constructed hillslopes, coupled with the development of new theory and methods to explicitly incorporate and couple the co-evolution of subsurface flow networks as intrinsic components of hydrological, ecological and geomorphic systems. This is a major community challenge that can now benefit from new experimental infrastructure, renewal of older infrastructure and recent advances in sensor systems and computational capacity but will also require a sustained and organized interdisciplinary approach.

Booth, D. B., Kraseski, K. A. and Rhett Jackson, C. (2014), Local-scale and watershed-scale determinants of summertime urban stream temperatures. Hydrol. Process., 28: 2427-2438. doi: 10.1002/hyp.9810

Abstract
The influence of urbanization on the temperature of small streams is widely recognized, but these effects are confounded by the great natural variety of their contributing watersheds. To evaluate the relative importance of local-scale and watershed-scale factors on summer temperatures in urban streams, hundreds of near-instantaneous temperature measurements throughout the central Puget Lowland, western Washington State, were collected during a single 2-h period in August in each of the years 1998–2001. Stream temperatures ranged from 8.9 to 27.5 C, averaging 15.4 C. Pairwise correlation coefficients between stream temperature and four watershed variables (total watershed area and the watershed percentages of urban development, upstream lakes, and permeable glacial outwash soils as an indicator of groundwater exchange) were uniformly very low. Akaike’s information criterion was applied to determine the best-supported sets of watershed-scale predictor variables for explaining the variability of stream temperatures. For the full four-year dataset, the only well-supported model was the global model (using all watershed variables); for the most voluminous single-year (1999) data, Akaike’s information criterion showed greatest support for per cent outwash (Akaike weight of 0.44), followed closely by per cent urban development + per cent outwash, per cent lake area only, and the global model. Upstream lakes resulted in downstream warming of up to 3 C; variability in riparian shading imposed a similar temperature range. Watershed urbanization itself is not the most important determining factor for summer temperatures in this region; even the long-recognized effects of riparian shading can be no more influential than those imposed by other local-scale and watershed-scale factors.

Bradford, Mark A., Robert J.Warren II, Petr Baldrian, Thomas W. Crowther, Daniel S. Maynard, Emily E. Oldfield,William R.Wieder, Stephen A.Wood and Joshua R. King, 2014. Climate Fails to Predict Wood Decomposition at Regional Scales. In Nature Climate Change, Letters, advanced online publication at www.nature.com/natureclimatechange

Abstract
Decomposition of organic matter strongly influences ecosystem carbon storage. In Earth-system models, climate is a predominant control on the decomposition rates of organic matter. This assumption is based on the mean response of decomposition to climate, yet there is a growing appreciation in other areas of global change science that projections based on mean responses can be irrelevant and misleading. We test whether climate controls on the decomposition rate of dead wood—a carbon stock estimated to represent 73 _ 6 Pg carbon globally—are sensitive to the spatial scale from which they are inferred. We show that the common assumption that climate is a predominant control on decomposition is supported only when local-scale variation is aggregated into mean values. Disaggregated data instead reveal that local-scale factors explain 73% of the variation in wood decomposition, and climate only 28%. Further, the temperature sensitivity of decomposition estimated from local versus mean analyses is 1.3-times greater. Fundamental issues with mean correlations were highlighted decades ago, yet mean climate–decomposition relationships are used to generate simulations that inform management and adaptation under environmental change. Our results suggest that to predict accurately how decomposition will respond to climate change, models must account for local-scale factors that control regional dynamics.

Brantley, S. T., Miniat, C. F., Elliott, K. J., Laseter, S. H. and Vose, J. M. (2014), Changes to southern Appalachian water yield and stormflow after loss of a foundation species. Ecohydrology. Doi: 10.1002/eco.1521

Abstract
Few studies have examined how insect outbreaks affect landscape-level hydrologic processes.We report the hydrologic effects of the invasive, exotic hemlock woolly adelgid (HWA) in a headwater catchment in the southern Appalachian Mountains. The study watershed experienced complete mortality of an evergreen tree species, Tsuga canadensis (L.) Carr. (eastern hemlock), after infestation was first detected in 2003. Hemlock mortality resulted in a ~6% reduction in basal area in the watershed, and this loss was primarily concentrated in riparian zones.We used a paired-watershed approach to quantify changes inwater yield and peak stormflow using streamflow data from the infested watershed and a nearby watershed with significantly lower hemlock basal area. We hypothesized that yieldwould increase shortly after hemlock infestation but decrease over the longer-term. Wefound that annual yield did not increase significantly in any year after infestation but decreased significantly by 12·0cm (~8%) in 2010. Monthly yield also decreased after infestation, but changes were limited to the dormant season. The decline in yield is likely to persist as hemlock is replaced by specieswith higher transpiration rates. Peakflow increased significantly after infestation during the two largest flow events in the post-infestation period. Changes in stormflow during extreme events may have been temporary as another evergreen, Rhododendron maximum, may have mitigated some of the changes after hemlock loss. Thus, streams draining watersheds where eastern hemlock has been lost due to HWA infestation demonstrate permanent reductions in yield and transient increases in peakflow during large-flow events. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Bryan Currinder, Kristen K. Cecala, Robert M. Northington & Michael E. Dorcas (2014) Response of stream salamanders to experimental drought in the southern Appalachian Mountains, USA, Journal of Freshwater Ecology, 29:4, 579-587, DOI: 10.1080/02705060.2014.938135

Abstract
Droughts act as significant disturbances to freshwater animals and their ecosystems. Given the impending threat of more frequent and persistent droughts because of global climate change, the lack of data on the responses of many aquatic animals to drought is a cause for concern. This study examined the body condition of the most commonly detected species (Desmognathus quadramaculatus) and abundance of commonly found species after two years of experimental drought in two first-order streams in the southern Appalachian Mountains. Our results indicated negative effectsof drought on the stream salamander community. The body condition of D. quadramaculatus larvae in experimental drought transects was significantly lower than larvae captured in control reaches, which may have resulted from lower macroinvertebrate production in experimental reaches. Additionally, larval D. quadramaculatus abundance declined 47% in experimental drought transects, and Eurycea wilderae larvae and D. ocoee adults were 70% less likely to be captured in experimental stream transects. Our findings contribute additional evidence that stream plethodontids have little resistance to drought. With extended droughts resulting from climate change more likely in the future, more research is necessary to determine if reduced body condition, production, and lowered abundance have effects on longterm population viability.

Burke, B.J. and N. Heynen (2014) Transforming Participatory Science into Socio-Ecological Praxis: Valuing Marginalized Environmental Knowledges in the Face of the Neoliberalization of Nature and Science. Environment and Society. 5: 7-27

Abstract
Citizen science and sustainability science promise the more just and democratic production of environmental knowledge and politics. In this review, we evaluate these participatory traditions within the context of (a) our theorization of how the valuation and devaluation of nature, knowledge, and people help to produce socioecological hierarchies, the uneven distribution of harms and benefi ts, and inequitable engagement within environmental politics, and (b) our analysis of how neoliberalism is reworking science and environmental governance. We fi nd that citizen and sustainability science oft en fall short of their transformative potential because they do not directly confront the production of environmental injustice and political exclusion, including the knowledge hierarchies that shape how the environment is understood and acted upon, by whom, and for what ends. To deepen participatory practice, we propose a heterodox ethicopolitical praxis based in Gramscian, feminist, and postcolonial theory and describe how we have pursued transformative praxis in southern Appalachia through the Coweeta Listening Project.

Butler, S.M., A.S. White, K.J. Elliott, and R.S. Seymour. 2014. Disturbance history and stand dynamics in secondary and old growth forests of the Southern Appalachian Mountains, USA. Journal of the Torrey Botanical Society 141(4):189-204

Abstract
Understanding the patterns of past disturbance allows further insight into the complex composition, structure, and function of current and future forests, which is increasingly important in a world where disturbance characteristics are changing. Our objectives were to define disturbance causes, rates (percent disturbance per decade), magnitudes and frequency (time since last disturbance) for both secondary and old-growth mixed-oak stands, and to determine if all mixed oak stands experience similar disturbance history. The study was located in two southern Appalachian forests in western North Carolina, USA: Coweeta Hydrologic Laboratory, a 2,185 ha experimental forest with some history of harvesting, and the Joyce Kilmer Wilderness, a 6,805 ha old-growth forest with no known harvesting. We used dendroecological techniques to evaluate the disturbance histories and create chronologies of these mixed-oak forests. Average decadal disturbance rates ranged from 4.3% to 13.8%, similar to rates common in eastern temperate forests (5% to 20%). The decades of peak recruitment common to several stands were the 1840s, which coincides with the historical accounts of a hurricane; the 1900s through the 1940s, which coincide with logging and elimination of Castanea dentata (Marshall) Borkh. by chestnut blight; and the 1960s, which coincides with drought and an elm spanworm infestation. The large peaks of disturbance were often synchronous and widespread, affecting stands across both Coweeta and Joyce Kilmer. However, there were also scattered pulses of disturbance unique to single stands, suggesting that localized events also played a role in the disturbance dynamics. Periods of constant low rates of disturbance present in all stands also indicate the importance of small canopy gaps in these forests. We found that stands similar in disturbance regimes were also similar in species composition. Results from our study provide information on how past disturbances, both regional and local events, have shaped the current forest. This understanding could help inform models to better predict how forests might respond to future climate (e.g., rising temperatures and increasing precipitation variability) and disturbance patterns (e.g., more frequent and severe events).

Caldwell, P., Segura, C., Laird, S.G., Sun, G., McNulty, S.G., Sandercock, M., Boggs, J. and Vose, J.M. 2014. Short-term stream water temperature observations permit rapid assessment of potential climate change impacts. Hydrological Processes. (DOI: 10.1002/hyp.10358)

Abstract
Assessment of potential climate change impacts on stream water temperature (Ts) across large scales remains challenging for resource managers because energy exchange processes between the atmosphere and the stream environment are complex and uncertain, and few long-term datasets are available to evaluate changes over time. In this study, we demonstrate how simple monthly linear regression models based on short-term historical Ts observations and readily available interpolated air temperature (Ta) estimates can be used for rapid assessment of historical and future changes in Ts. Models were developed for 61 sites in the southeastern USA using =18 months of observations and were validated at sites with longer periods of record. The Ts models were then used to estimate temporal changes in Ts at each site using both historical estimates and future Ta projections. Results suggested that the linear regression models adequately explained the variability in Ts across sites, and the relationships between Ts and Ta remained consistent over 37 years. We estimated that most sites had increases in historical annual mean Ts between 1961 and 2010 (mean of +0.11°C decade^-1). All 61 sites were projected to experience increases in Ts from 2011 to 2060 under the three climate projections evaluated (mean of +0.41°C ^1). Several of the sites with the largest historical and future Ts changes were located in ecoregions home to temperature-sensitive fish species. This methodology can be used by resource managers for rapid assessment of potential climate change impacts on stream water temperature.

Cecala, K. K., Lowe, W. H. and Maerz, J. C. (2014), Riparian disturbance restricts in-stream movement of salamanders. Freshwater Biology, 59: 2354-2364. doi: 10.1111/fwb.12439

Abstract
1. Long-term population persistence or population rescue require dispersal from other source populations. Barriers to movement can effectively fragment and isolate populations, reducing persistence and recolonisation. For stream organisms that depend heavily on movement within dendritic networks, research is needed to identify and estimate the effects of such barriers on connectivity. 2. We used capture–mark–recapture of displaced larval and adult salamanders to estimate return rates across gaps (length 13–85 m) in the riparian canopy and thus to assess the fragmentation of salamander populations within otherwise fully forested catchments. 3. Relative to salamanders in fully forested reaches, displaced salamanders were 86% less likely to return to their capture location when required to cross gaps in the canopy as short as 13 m, and the likelihood of return declined with increasing gap length. The effects of gaps on return rates were consistent among life stages and for up- and downstream movement. 4. Our study suggests that riparian disturbance can reduce permeability to salamanders, even in the absence of additional land-use change. Because anthropogenic features, such as roads and powerlines, frequently cross small streams, the accumulation of apparently small land-cover changes has the potential to reduce continuous populations to small fragments with limited connectivity.

Clark, J.S., D.M. Bell, M.C. Kwit, and K. Zhu. 2014. Competition-interaction landscapes for the joint response of forests to climate change. Global Change Biology, 20, 1979-1991.

Abstract
The recent global increase in forest mortality episodes could not have been predicted from current vegetation models that are calibrated to regional climate data. Physiological studies show that mortality results from interactions between climate and competition at the individual scale. Models of forest response to climate do not include interactions because they are hard to estimate and require long-term observations on individual trees obtained at frequent (annual) intervals. Interactions involve multiple tree responses that can only be quantified if these responses are estimated as a joint distribution. A new approach provides estimates of climate–competition interactions in two critical ways, (i) among individuals, as a joint distribution of responses to combinations of inputs, such as resources and climate, and (ii) within individuals, due to allocation requirements that control outputs, such as demographic rates. Application to 20 years of data from climate and competition gradients shows that interactions control forest responses, and their omission from models leads to inaccurate predictions. Species most vulnerable to increasing aridity are not those that show the largest growth response to precipitation, but rather depend on interactions with the local resource environment. This first assessment of regional species vulnerability that is based on the scale at which climate operates, individual trees competing for carbon and water, supports predictions of potential savannification in the southeastern US.

Cohen, Emily B, Scott M. Pearson and Frank R. Moore. 2014. Effects of landscape composition and configuration on migrating songbirds: inference from an individual-based model. Ecological Applications 24(1):169-180.

Abstract
The behavior of long-distance migrants during stopover is constrained by the need to quickly and safely replenish energetic reserves. Replenishing fuel stores at stopover sites requires adjusting to unfamiliar landscapes with little to no information about the distribution of resources. Despite their critical importance to the success of songbird migration, the effects of landscape composition and configuration on fuel deposition rates (FDR [g/d]), the currency of migration, has not been tested empirically. Our objectives were to understand the effects of heterogeneous landscapes on FDR of forest-dwelling songbirds during spring migration. The results of field experiments were used to parameterize a spatially explicit, individual-based model of forest songbird movement and resulting FDR. Further field experiments were used to validate the results from the individual-based model. In simulation experiments, we altered a Gulf South landscape in a factorial design to predict the effects of future patterns under different scenarios of land use change in which the abundance of high-quality hardwood habitat and the spatial aggregation of habitat varied. Simulated FDR decreased as the amount of hardwood in the landscape decreased from 41% to 22% to 12%. Further, migrants that arrived in higher-quality habitat types gained more mass. Counter to our expectations, FDR was higher with lower spatial aggregation of habitat. Differences in refueling rates may be most influenced by whether or not an individual experiences an initial searching cost after landing in poor-quality habitat. Therefore, quickly locating habitat with sufficient food resources at each stopover may be the most important factor determining a successful migration. Our findings provide empirical evidence for the argument that hardwood forest cover is a primary determinant of the quality of a stopover site in this region. This study represents the first effort to empirically quantify FDRs based on the configuration of landscapes.

Creed, I.F., Spargo, A.T., Jones, J.A., Buttle, J.M., Adams, M.B., Beall, F.D., Booth, E., Campbell, J., Clow, D., Elder, K., Green, M.B., Grimm, N.B., Miniat, C., Ramlal, P., Saha, A., Sebestyen, S., Spittlehouse, D., Sterling, S., Williams, M.W., Winkler, R., and Yao, H. 2014. Changing forest water yields in response to climate warming: Results from long-term experimental watershed sites across North America. Global Change Biology. 20(10): 3191-3208. DOI: 10.1111/gcb.12615

Abstract
Climate warming is projected to affect forest water yields bu t the effects are expected to vary. We investigated how forest type and age affect water yield resilience to climate warming. To answer this quest ion, we examined the variability in his- torical water yields at long-term exper imental catchments across Canada and the United States over 5-year cool and warm periods. Using the theoretical framework of the Budyko curve, we calculated the effects of climate warming on the annual partitioning of precipitation ( P ) into evapotranspiration (ET) and water yield. Deviation ( d ) was defined as a catch- ment’s change in actual ET divided by P [AET/ P ; evaporative index (EI)] coincident with a shift from a cool to a warm period – a positive d indicates an upward shift in EI and smaller than expected water yields, and a negative d indicates a downward shift in EI and larger than expected water yields. Elasticity was defined as the ratio of interannual variation in potential ET divided by P (PET/ P ; dryness index) to interannual variation in the EI – high elasticity indicates low d despite large range in drying index (i.e., resili ent water yields), low elasticity indicates high d despite small range in dry- ing index (i.e., nonresilient water yields). Although the data needed to fully evaluate ecosystems based on these metrics arelimited,wewereabletoidentifysomecharacteristicsofre sponse among forest types. Alpine sites showed the greatest sensitivity to climate warming with any warming leading to in creased water yields. Conifer forests included catchments with lowest elasticity and stabl e to larger water yields. Deciduous forests inclu ded catchments with intermediate elasticity and stable to smaller water yields. Mixed coniferous/decidu ous forests included catchmen ts with highest elasticity and stable water yields. Forest type appeared to influence the re silience of catchment water yi elds to climate warming, with conifer and deciduous catchments more susceptible to clim ate warming than the more diverse mixed forest catchments

Diez, Jeffrey M., Itamar Giladi, Robert Warren and H. Ronald Pulliam 2014. Probabilistic and Spatially Variable Niches Inferred from Demography. In Journal of Ecology, pp. 1-6, online publication.

Abstract
1. Mismatches between species distributions and habitat suitability are predicted by niche theory and have important implications for forecasting how species may respond to environmental changes. Quantifying these mismatches is challenging, however, due to the high dimensionality of species niches and the large spatial and temporal variability in population dynamics. 2. Here, we explore how probabilistic assessments of habitat suitability based on demographic models may be used to better bridge niche theory and population dynamics. We use integral projection models (IPMs) to predict population growth rates for a terrestrial orchid in response to environmental variables. By parameterizing these IPMs with hierarchical models, we develop a spatially variable measure of a species’ demographic niche, which can then be compared against its distribution to test ideas about what factors control a species’ distribution. 3. We found that demographic suitability of sites was not well correlated with the orchid’s distribution at local scales, with many absences from microsites of high predicted suitability and occurrences in sites with low predicted suitability. However, at the population scale, abundance was positively correlated with demographic suitability of the sites. These results are consistent with dispersal limitation and source–sink dynamics at small scales but stronger distribution-suitability matching at larger landscape scales. 4. Synthesis. The relationships between species distributions and demographic performance underlie basic niche theory and have important implications for predicting responses to a changing environment. The complexities of these relationships will require approaches that can encapsulate what we know in probabilistic terms and allow for spatially varying niche relationships.

Dodds, W.K., Collins, S., Hamilton, S.K., Tank, J.L., Johnson, S.L., Webster, J., Whiles, M.R., Rantala, M., McDowell, W.H., Peterson, S., Riis, T., Crenshaw, C.L., Thomas, C., Cheever, B.M., Flecker, A., Griffiths, N., Crowl, T., Rosi-Marshall, E.J., El-Sabaawi, R. and Marti, E. 2014. You are not always what we think you eat: selective assimilation across multiple whole-stream isotopic tracer studies. Ecology. 95:2757-2767.

Abstract
Analyses of 21 15N stable isotope tracer experiments, designed to examine food web dynamics in streams around the world, indicated that the isotopic composition of food resources assimilated by primary consumers (mostly invertebrates) poorly reflected the presumed food sources. Modeling indicated that consumers assimilated only 33–50% of the N available in sampled food sources such as decomposing leaves, epilithon, and fine particulate detritus over feeding periods of weeks or more. Thus, common methods of sampling food sources consumed by animals in streams do not sufficiently reflect the pool of N they assimilate. Isotope tracer studies, combined with modeling and food separation techniques, can improve estimation of N pools in food sources that are assimilated by consumers. Food web studies that use putative food samples composed of actively cycling (more readily assimilable) and refractory (less assimilable) N fractions may draw erroneous conclusions about diets, N turnover, and trophic linkages of consumers. By extension, food web studies using stoichiometric or natural abundance approaches that rely on an accurate description of food-source composition could result in errors when an actively cycling pool that is only a fraction of the N pool in sampled food resources is not accounted for.

Dodds, W.K., Webster, J., Crenshaw, C.L., Helton, A.M., O'Brien, J.M., Marti, E., Hershey, A.E., Tank, J.L., Burgin, A.J., Grimm, N.B., Hamilton, S.K., Sobata, D.J., Poole, G.C., Beaulieu, J.J., Johnson, L.T., Ashkenas, L.R., Hall, R.O., Johnson, S.L., Wollheim, W.M. and Bowden, W.B. 2014. The Lotic Intersite Nitrogen Experiments: an example of successful ecological research collaboration. Freshwater Science. 33(700-710).

Abstract
Collaboration is an essential skill for modern ecologists because it brings together diverse expertise, viewpoints, and study systems. The Lotic Intersite Nitrogen eXperiments (LINX I and II), a 17-y research endeavor involving scores of early- to late-career stream ecologists, is an example of the benefits, challenges, and approaches of successful collaborative research in ecology. The scientific success of LINX reflected tangible attributes including clear scientific goals (hypothesis-driven research), coordinated research methods, a team of cooperative scientists, excellent leadership, extensive communication, and a philosophy of respect for input from all collaborators. Intangible aspects of the collaboration included camaraderie and strong team chemistry. LINX further benefited from being part of a discipline in which collaboration is a tradition, clear data-sharing and authorship guidelines, an approach that melded field experiments and modeling, and a shared collaborative goal in the form of a universal commitment to see the project and resulting data products through to completion.

Dymond, Salli F., Aust, W. Michael, Prisley, Stephen P., Eisenbies, Mark H., Vose, James M. (2014) Application of a Distributed Process-Based Hydrologic Model to Estimate the Effects of Forest Road Density on Stormflows in the Southern Appalachians, Forest Science, 60:6 1213-1223, doi:10.5849/forsci.13-60

Abstract
Managed forests have historically been linked to watershed protection and flood mitigation. Research indicates that forests can potentially minimize peak flows during storm events, yet the relationship between forests and flooding is complex. Forest roads, usually found in managed systems, can potentially magnify the effects of forest harvesting on water yields. The distributed hydrology-soil-vegetation model was successfully calibrated at an hourly time step for a 760-ha watershed in the Blue Ridge Mountains of North Carolina. The impacts of forest road density were modeled using uniform input parameters but changing road densities. Road densities tested were 0.5, 1.0, 3.0, 4.3, 6.0, and 12.0 km km2. Results indicate that increases in road density increased average stormflow volume by as much as 17.5% when road densities increased from 0.5 to 4.3 km km2 (P  0.05). Overall, model simulations suggest that minimizing road density necessitated by the land use and appropriate forest road best management practices can be used to minimize impacts on stormflow.

Elliott, K.J., J.M. Vose, and D. Rankin (2014). Herbaceous-layer species composition and richness of mesophytic cove forests in the southern Appalachians: Synthesis and Knowledge Gaps. Journal of the Torrey Botanical Society. 141 (1), 39-71

Abstract
We synthesized the current information on mesophytic cove forests in the southern Appalachians, assessed the range of variation in herb species composition and diversity in stands with different disturbance histories and environmental conditions, identified key knowledge gaps, and suggested approaches to fill these knowledge gaps. The purpose of this synthesis was to provide information to forest managers to help make decisions about conservation assessments and strategies for rich cove forests in the southern Appalachians. An important finding is that no single study or data set can provide conclusive evidence or clear management strategies. However, an overriding conclusion is that the magnitude of impact and the management actions necessary to restore herbaceous communities are directly proportional to the severity of disturbance, current condition (e.g., presence of Rhododendron), site heterogeneity, and historical land use (e.g., agricultural activity). These factors plus a host of other stressors (e.g., climate variability, air pollution, invasives) are likely to have a strong influence on the highly variable patterns observed when comparing herbaceous diversity of ‘old-growth’ or uncut forests to human disturbed forests (e.g., cutting, air pollution, conversion, invasive plants or insects). Results from this review reinforce our premise that factors controlling herbaceous species presence and abundance are highly complex, thus broad generalizations about the impacts of a single factor such as logging should be interpreted with caution. Of the stressors known to affect forest trees (e.g., pests and pathogens, acidic deposition, air pollution, drought, and wind), little to no information exists on how these same stressors will affect herbaceous plants. A limited number of studies have examined the demography or physiology of forest herbs, particularly across all life stages. While the demography of a few genera have been studied (e.g., Hexastylis, Asarum, Trillium, Arisaema, Goodyera, Hepatica), little to no information exists for the majority of woodland herbs. Species identity is important when considering management of rich cove forests. Diversity may increase following canopy disturbances that favor recruitment of early-seral herbaceous species; therefore, simple indices of diversity (H', S, and E) are not the best measure of recovery in mesophytic rich coves, particularly where shade-adapted ‘rich-cove indicator’ species have been replaced by these species. Species-specific life histories and the influence of prevailing site conditions are important lines of research for understanding recovery and sustainability of mesophytic rich cove forests.

Fraterrigo, J.M., Wagner, S. and Warren, R.J. II. 2014. Local-scale biotic interactions embedded in macroscale climate drivers suggest Eltonian noise hypothesis distribution patterns for an invasive grass. Ecology Letters. 17:1447-1454.

Abstract
A hierarchical view of niche relations reconciles the scale-dependent effects of abiotic and biotic processes on species distribution patterns and underlies most current approaches to distribution modeling. A key prediction of this framework is that the effects of biotic interactions will be averaged out at macroscales – an idea termed the Eltonian noise hypothesis (ENH). We test this prediction by quantifying regional variation in local abiotic and biotic niche relations and assess the role of macroclimate in structuring biotic interactions, using a non-native invasive grass, Microstegium vimineum, in its introduced range. Consistent with hierarchical niche relations and the ENH, macroclimate structures local biotic interactions, while local abiotic relations are regionally conserved. Biotic interactions suppress M. vimineum in drier climates but have little effect in wetter climates. A similar approach could be used to identify the macroclimatic conditions under which biotic interactions affect the accuracy of local predictions of species distributions.

Hartman, M.D., Baron, J.S., Ewing, H.A. and Weathers, K.C. 2014. Combined global change effects on ecosystem processes in nine U.S. topographically complex areas. Biogeochemistry. (DOI: 10.1007/s10533-014-9950-9.)

Abstract
Concurrent changes in climate, atmospheric nitrogen (N) deposition, and increasing levels of atmospheric carbon dioxide (CO2) affect ecosystems in complex ways. The DayCent-Chem model was used to investigate the combined effects of these human-caused drivers of change over the period 1980–2075 at seven forested montane and two alpine watersheds in the United States. Net ecosystem production (NEP) increased linearly with increasing N deposition for six out of seven forested watersheds; warming directly increased NEP at only two of these sites. Warming reduced soil organic carbon storage at all sites by increasing heterotrophic respiration. At most sites, warming together with high N deposition increased nitrous oxide (N2O) emissions enough to negate the greenhouse benefit of soil carbon sequestration alone, though there was a net greenhouse gas sink across nearly all sites mainly due to the effect of CO2 fertilization and associated sequestration by plants. Over the simulation period, an increase in atmospheric CO2 from 350 to 600 ppm was the main driver of change in net ecosystem greenhouse gas sequestration at all forested sites and one of two alpine sites, but an additional increase in CO2 from 600 to 760 ppm produced smaller effects. Warming either increased or decreased net greenhouse gas sequestration, depending on the site. The N contribution to net ecosystem greenhouse gas sequestration averaged across forest sites was only 5–7 % and was negligible for the alpine. Stream nitrate (NO3 −) fluxes increased sharply with N-loading, primarily at three watersheds where initial N deposition values were high relative to terrestrial N uptake capacity. The simulated results displayed fewer synergistic responses to warming, N-loading, and CO2 fertilization than expected. Overall, simulations with DayCent-Chem suggest individual site characteristics and historical patterns of N deposition are important determinants of forest or alpine ecosystem responses to global change.

Hwang, T., Band, L.E., Miniat, C.F., Song, C., Bolstad, P.V., Vose, J.M. and Love, J.P. 2014. Divergent phenological response to hydroclimate variability in forested mountain watersheds. Global Change Biology. 20:2580-2595. (DOI:10.1111/gcb.12556)

Abstract
Mountain watersheds are primary sources of freshwater, carbon sequestration, and other ecosystem services. There is significant interest in the effects of climate change and variability on these processes over short to long time scales. Much of the impact of hydroclimate variability in forest ecosystems is manifested in vegetation dynamics in space and time. In steep terrain, leaf phenology responds to topoclimate in complex ways, and can produce specific and measurable shifts in landscape forest patterns. The onset of spring is usually delayed at a specific rate with increasing elevation (often called Hopkins' Law; Hopkins, 1918), reflecting the dominant controls of temperature on greenup timing. Contrary with greenup, leaf senescence shows inconsistent trends along elevation gradients. Here, we present mechanisms and an explanation for this variability and its significance for ecosystem patterns and services in response to climate. We use moderate-resolution imaging spectro-radiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data to derive landscape-induced phenological patterns over topoclimate gradients in a humid temperate broadleaf forest in southern Appalachians. These phenological patterns are validated with different sets of field observations. Our data demonstrate that divergent behavior of leaf senescence with elevation is closely related to late growing season hydroclimate variability in temperature and water balance patterns. Specifically, a drier late growing season is associated with earlier leaf senescence at low elevation than at middle elevation. The effect of drought stress on vegetation senescence timing also leads to tighter coupling between growing season length and ecosystem water use estimated from observed precipitation and runoff generation. This study indicates increased late growing season drought may be leading to divergent ecosystem response between high and low elevation forests. Landscape-induced phenological patterns are easily observed over wide areas and may be used as a unique diagnostic for sources of ecosystem vulnerability and sensitivity to hydroclimate change.

Jackson, C.R., Bitew, M. and Du, E. 2014. When interflow also percolates: Downslope travel distances and hillslope process zones. Hydrological Processes. 28:3195-3200. (DOI: 10.1002/hyp.10158)

Jackson, M.M., Turner, M.G. and Pearson, S.M. 2014. Logging legacies affect insect pollinator communities in southern Appalachian forests. Southeastern Naturalist. 13(2):317-336. (DOI: http://dx.doi.org/10.1656/058.013.0213)

James S. Clark, Alan E. Gelfand, Christopher W. Woodall, and Kai Zhu 2014. More than the sum of the parts: forest climate response from joint species distribution models. Ecological Applications 24:990 - 999. http://dx.doi.org/10.1890/13-1015.1

Abstract
The perceived threat of climate change is often evaluated from species distribution models that are fitted to many species independently and then added together. This approach ignores the fact that species are jointly distributed and limit one another. Species respond to the same underlying climatic variables, and the abundance of any one species can be constrained by competition; a large increase in one is inevitably linked to declines of others. Omitting this basic relationship explains why responses modeled independently do not agree with the species richness or basal areas of actual forests. We introduce a joint species distribution modeling approach (JSDM), which is unique in three ways, and apply it to forests of eastern North America. First, it accommodates the joint distribution of species. Second, this joint distribution includes both abundance and presence– absence data. We solve the common issue of large numbers of zeros in abundance data by accommodating zeros in both stem counts and basal area data, i.e., a new approach to zero inflation. Finally, inverse prediction can be applied to the joint distribution of predictions to integrate the role of climate risks across all species and identify geographic areas where communities will change most (in terms of changes in abundance) with climate change. Application to forests in the eastern United States shows that climate can have greatest impact in the Northeast, due to temperature, and in the Upper Midwest, due to temperature and precipitation. Thus, these are the regions experiencing the fastest warming and are also identified as most responsive at this scale.

Jensen, C. K., et al. (2014). Scales and arrangements of large wood in first- through fifth-order streams of the Blue Ridge Mountains. Physical Geography 35(6): 532-560.

Abstract
Large wood frequency and volume were examined as a function of landscape characteristics at different spatial and temporal scales in 50 reaches of the Upper Little Tennessee River basin with drainage areas ranging from 0.3 to 30.1 km2. Riparian forest cover was described laterally at the reach scale and longitudinally 1 km upstream in all tributaries. Riparian cover was analyzed with geomorphic and additional landscape variables to isolate factors that most influence wood in streams. Forested area immediately surrounding the reach was the strongest predictor of wood frequency and volume, although upstream riparian cover can explain additional variation in wood distributions. An optimal forested buffer width around the stream for large wood was not evident. The relationship between the riparian forest and wood weakens in bigger channels, as fluvial transport of pieces increases. Resurveys demonstrate that large wood is most dynamic in wide, forested reaches and changes function during floods to store sediment and organic matter.

Joseph E. Kirsch & James T. Peterson (2014) A Multi-Scaled Approach to Evaluating the Fish Assemblage Structure Within Southern Appalachian Streams, Transactions of the American Fisheries Society, 143:5, 1358-1371, 10.1080/00028487.2014.935478.

Abstract
There is considerable uncertainty about the relative roles of stream habitat and landscape characteristics in structuring stream-fish assemblages. We evaluated the relative importance of environmental characteristics on fish occupancy at the local and landscape scales within the upper Little Tennessee River basin of Georgia and North Carolina. Fishes were sampled using a quadrat sample design at 525 channel units within 48 study reaches during two consecutive years. We evaluated species–habitat relationships (local and landscape factors) by developing hierarchical, multispecies occupancy models. Modeling results suggested that fish occupancy within the Little Tennessee River basin was primarily influenced by stream topology and topography, urban land coverage, and channel unit types. Landscape scale factors (e.g., urban land coverage and elevation) largely controlled the fish assemblage structure at a stream-reach level, and local-scale factors (i.e., channel unit types) influenced fish distribution within stream reaches. Our study demonstrates the utility of a multi-scaled approach and the need to account for hierarchy and the interscale interactions of factors influencing assemblage structure prior to monitoring fish assemblages, developing biological management plans, or allocating management resources throughout a stream system.

Joshua S. Rice & Ryan E. Emanuel (2014): Landscape position and spatial patterns in the distribution of land use within the southern Appalachian Mountains, Physical Geography

Abstract
Understanding the forces that influence the distribution of land use and land-use change (LUC) is an essential step in developing effective strategies for managing these issues. We examined the influence of landscape position on spatial patterns in land-use distribution within the Little Tennessee River Basin (LTRB) of the southern Appalachian Mountains. We show that landscape position, defined with respect to both natural and anthropogenic spatial variables, provides for the identification of statistically significant differences in the distribution of common forms of land use in the study region. Using the same variables, significant differences in the landscape positions subject to land-use change in the LTRB are also examined. These results suggest landscape position exerts a strong influence on the distribution of different forms of land use and the likeliness of given area undergoing LUC. The approach presented here, of considering land use as a function of landscape position that responds to both natural and anthropogenic forces, may prove useful in aiding the development of future strategies to address the consequences of land use in many regions.

Kim, Dohyoung; Oren, Ram; Oishi, A. Christopher; Hsieh, Cheng-I; Phillips, Nathan; Novick, Kimberly A.; Stoy, Paul C. 2014. Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest. Agricultural and Forest Meteorology. 187: 62-27.

Abstract
Wind velocity (U) within and above forest canopies can alter the coupling between the vapor-saturated sub-stomatal airspace and the drier atmosphere aloft, thereby influencing transpiration rates. In practice, however, the actual increase in transpiration with increasing U depends on the aerodynamic resistance (RA) to vapor transfer compared to canopy resistance to water vapor flux out of leaves (RC, dominated by stomatal resistance, Rstom), and the rate at which RA decreases with increasing U. We investigated the effect of U on transpiration at the canopy scale using filtered meteorological data and sap flux measurements gathered from six diverse species of a mature broadleaved deciduous forest. Only under high light conditions, stand transpiration (EC) increased slightly (6.5%) with increasing U ranging from ~0.7 to ~4.7 m s-1. Under other conditions, sap flux density (Js) and EC responded weakly or did not change with U. RA, estimated from Monin–Obukhov similarity theory, decreased with increasing U, but this decline was offset by increasing RC, estimated from a rearranged Penman–Monteith equation, due to a concurrent increase in vapor pressure deficit (D). The increase of RC with D over the observed range of U was consistent with increased Rstom by ~40% based on hydraulic theory. Except for very rare half-hourly values, the proportion of RA to total resistance (RT) remained <15% over the observed range of conditions. These results suggest that in similar forests and conditions, the direct effect of U reducing RA and thus increasing transpiration is negligible. However, the observed U–D relationship and its effect on Rstom must be considered when modeling canopy photosynthesis.

Lin, L. and Webster, J.R. 2014. Detritus decomposition and nutrient dynamics in a forested headwater stream. Ecological Modeling. (DOI: 10.1016/j.ecolmodel.2013.12.013)

Mitchell, R.J., Y. Liu, J.J. O'Brien, K.J. Elliott, G. Starr, C. Ford Miniat, and J.K. Hiers (2014). Future climate and fire interactions in the southeastern region of the United States. Forest Ecology and Management. 327 316-326

Abstract
Fire has a profound, though paradoxical influence on landscapes of the southeastern U.S.; it simultaneously maintains native biodiversity and ecosystem processes but also threatens silvicultural resources and human landscapes. Furthermore, since the majority of the southern landscape is heavily influenced by human activities, contemporary fire regimes are human managed disturbances within extant firedependent ecosystems. Though there is considerable uncertainty in climate projections for the southeastern U.S., climate change will likely impact both prescribed fire and wildfire. In this review, we synthesize climate change-fire interactions, discuss the impacts of uncertainty in a human-dominated landscape, and illuminate how both climate change projections and their uncertainties might impact our ability to manage forests in the Southeast. We define the Southeast region as consisting of the Gulf Coastal Plain, Lower Atlantic Coastal Plain, Piedmont and southern Appalachians and associated subregions. This region has the greatest area burned by prescribed fire, the highest number of wildfires in the continental U.S. and contains globally significant hotspots of biodiversity, much of which is dependent on frequent fire. The use of prescribed fire as a management tool depends on a suite of weather and fuel conditions which are affected by climate. Over the next five decades, general circulation models (GCMs) consistently predict air temperature to increase by 1.5–3 C in the Southeast. Precipitation forecasts are more uncertain with respect to the mean; but, most models predict an increase in precipitation variability. Increases in the likelihood of severe droughts may increase wildfire occurrence while simultaneously limiting the implementation of prescribed burning by restricting the number of days within current prescription guidelines. While the Southeast has among the highest potential for C storage and sequestration, a reduction in C sequestration capacity due to increasing disturbances such as drought, insect infestations, hurricanes and fire, is possible. The potential for long-term shifts in forest composition from climate-altered fire regimes if coupled with an increased potential for wildfire occurrence could reduce quality and quantity of water released from forests at times when demand for high quality water will intensify for human use. Furthermore, any reduction in prescribed burning is likely to result in decreased biological diversity, particularly in the Coastal Plain, a global hotspot of biodiversity. Lastly, more future area burned by wildfire rather than prescribed fire has the potential to negatively influence regional air quality. Mitigating the negative effects of climate change-fire interactions would require actively exploiting favorable seasonal and inter-annual climate windows. Monitoring the type conversions of agricultural and fiber production forest will be critical for long-term projections of fire risk and watershed impacts of altered fire regimes.

Mohan JE, et al., (2014) Mycorrhizal fungi mediation of terrestrial ecosystem responses to global change: mini-review, Fungal Ecology, http://dx.doi.org/10.1016/j.funeco.2014.01.005

Abstract
Mycorrhizal fungi are responsible for most nutrient uptake by the majority of land plants. As such, mycorrhizas are increasingly recognized as important drivers of terrestrial ecosystem processes, and may mediate ecosystem responses to environmental change. Here we review published studies that explicitly address the role of mycorrhizal influence on ecosystem responses such as biogeochemical fluxes and pools, ecosystem productivity, and dominant vegetative growth responses to global change. We find that most studies are of limited duration (1 yr) and geographical distribution. A strong bias in the literature regarding the location of studied ecosystems, with large parts of the globe, such as highlyweathered soil systems in the tropics, subtropics and warm temperate biomes, accounting for w30 % of the global land base, greatly under-investigated. In terms of mediating ecosystem responses to global change, mycorrhizaleplant symbioses exhibit conflicting responses although some generalities do exist. Plants often shift carbon allocation belowground and the activities of mycorrhizal associates are frequently enhanced at elevated atmospheric CO2 conditions, but the direct effects for ecosystem dynamics are less clear. Mycorrhizal associations reduce plant stress under drought conditions. How mycorrhizal root colonization responds to nitrogen deposition depends on the type of mycorrhizas and background levels of soil nitrogen and phosphorus. The capacity of mycorrhizas for mediating plant and ecosystem responses to warming are varied, but over 60% of these studies found increased mycorrhizal abundance and decreased mycorrhizal activity with warmer temperatures. This review suggests the role mycorrhizal fungi play in ecosystems responding to global change is not well understood. We emphasize the need for more research in this emerging field, as such responses and ecosystem feedbacks to Earth’s climate system are of concern to multiple scientific disciplines and society.

Novick, K.A., Brantley, S.T., Miniat, C.F., Walker, J. and Vose, J.M. 2014. Inferring the contribution of advection to total ecosystem scalar fluxes over a tall forest in complex terrain. Agricultural and Forest Meteorology. 185:1-13. (DOI: http://dx.doi.org/10.1016/j.agrformet.2013.10.010)

Abstract
Multiple data streams from a new flux tower located in complex and heterogeneous terrain at theCoweeta Hydrologic Laboratory (North Carolina, USA) were integrated to identify periods of advectiveflow regimes. Drainage flows were expected a priori, due to the location of the measurement site at thebase of a long, gently-sloping valley. Drainage flow was confirmed by examining vertical profile mea-surements of wind direction and by estimating vertical advection fluxes. The vertical advection flux ofCO2was most significant in early morning (000–0600 h) during the growing season, when it averaged∼5 _mol m−2s−1. Horizontal advection flux of CO2was not directly measured in this study; however, anexpected exponential relationship between nocturnal ecosystem respiration (RE) and air temperaturewas recovered when horizontal advection of CO2was assumed to be negatively correlated to verticaladvection, or when data were limited to periods when measured vertical advection fluxes were small.Taken together, these data imply the presence of a negative horizontal advection CO2flux during noc-turnal periods characterized by positive vertical advection of CO2. Daytime periods were characterizedby consistent anabatic (up-valley) flows in mid- to late-morning (0500–1200 h) and consistent katabatic(down-valley) flows in the afternoon. A combination of above-canopy flux profile measurements, energybalance closure estimates, and flux footprint estimates suggest that during periods of up-valley windflow, the flux footprint frequently exceeds the ecosystem dimensions, and horizontal advection fluxesrelated to landscape heterogeneity were a significant component of the total ecosystem flux of CO2. Weused sap flux from individual trees beneath the tower to explore diurnal patterns in stomatal conductancein order to evaluate gapfilling approaches for the unreliable morning data. The relationship between sto-matal conductance and vapor pressure deficit was similar in morning and afternoon periods, and weconclude that gapfilling morning data with models driven by afternoon data is a reasonable approachat this site. In general, results were consistent with other studies showing that the advection and windflow regimes in complex terrain are highly site specific; nonetheless, the site characterization strategydeveloped here, when used together with independent estimates of components of the ecosystem carbonflux, could be generally applied in other sites to better understand the contribution of advection to thetotal ecosystem flux.

Oishi, A.C., Palmroth, S., Johnsen, K.H., McCarthy, H.R. and Oren, R. 2014. Sustained effects of atmospheric [CO2] and nitrogen availability on forest soil CO2 efflux. Global Change Biology. 20:1146-1160.

Abstract
Soil CO2 efflux (Fsoil) is the largest source of carbon from forests and reflects primary productivity as well as how carbon is allocated within forest ecosystems. Through early stages of stand development, both elevated [CO2] and availability of soil nitrogen (N; sum of mineralization, deposition, and fixation) have been shown to increase gross primary productivity, but the long-term effects of these factors on Fsoil are less clear. Expanding on previous studies at the Duke Free-Air CO2 Enrichment (FACE) site, we quantified the effects of elevated [CO2] and N fertilization on Fsoil using daily measurements from automated chambers over 10 years. Consistent with previous results, compared to ambient unfertilized plots, annual Fsoil increased under elevated [CO2] (ca. 17%) and decreased with N (ca. 21%). N fertilization under elevated [CO2] reduced Fsoil to values similar to untreated plots. Over the study period, base respiration rates increased with leaf productivity, but declined after productivity saturated. Despite treatment-induced differences in aboveground biomass, soil temperature and water content were similar among treatments. Interannually, low soil water content decreased annual Fsoil from potential values – estimated based on temperature alone assuming nonlimiting soil water content – by ca. 0.7% per 1.0% reduction in relative extractable water. This effect was only slightly ameliorated by elevated [CO2]. Variability in soil N availability among plots accounted for the spatial variability in Fsoil, showing a decrease of ca. 114 g C m _2 yr _1 per 1 g m _2 increase in soil N availability, with consistently higher Fsoil in elevated [CO2] plots ca. 127 g C per 100 ppm [CO2] over the +200 ppm enrichment. Altogether, reflecting increased belowground carbon partitioning in response to greater plant nutritional needs, the effects of elevated [CO2] and N fertilization on Fsoil in this stand are sustained beyond the early stages of stand development and through stabilization of annual foliage production.

Richard C. Bruce (2014) Reproductive Allometry in Three Species of Dusky Salamanders. Copeia: September 2014, Vol. 14, No. 3, pp. 419-427.

Abstract
Desmognathus comprises 21 currently recognized species of salamanders in eastern North America. Assemblages of 3–6 species occur in the Appalachian Mountains, wherein the larger species are more aquatic and the smaller more terrestrial. Adaptive divergence along the habitat gradient from stream to forest involves variation in such life-history traits as age and size at metamorphosis and maturation, survival, propagule size, and fecundity. In this study I examined the tradeoff between egg size and clutch size in North Carolina populations of D. santeetlah, D. ocoee, and D. aeneus, with special emphasis on the latter two species. Traits evaluated included standard length, body mass, trunk volume, egg size, clutch size, and clutch volume. For D. aeneus and D. ocoee, regressions of log-transformed values of body mass and trunk volume on standard length, and trunk volume on body mass, indicated strong similarity between the species in those body proportions that ostensibly constrain female reproductive effort. In all three species bivariate linear regressions of log-transformed values of clutch dimensions on body size suggested little correlation between egg size and body size within species, although larger species had larger eggs, larger clutches, and greater clutch volumes. An apparent interspecific tradeoff between egg size and clutch size in D. aeneus and D. ocoee suggested a common pattern in the relationship between body size and reproductive effort in these species. The results provided further evidence of a high level of life-history invariance in the genus Desmognathus, embodied in tradeoffs, which may stem from morphological conservatism related to specializations of the musculo-skeletal system.

Rocca, Monique E., Chelcy Ford Miniat and Robert J. Mitchell (2014). Introduction to the regional assessments: Climate change, wildfire, and forest ecosystem services in the USA. Forest Ecology and Management. 327 265-268

Abstract
Fires have influenced and shaped vegetation ever since the climate evolved to provide both ignition sources and oxygen (Bowman et al., 2009). Fire has been one of the most frequent and impactful disturbances to ecosystems globally, and thus one of the major regulators of forest composition, function and dynamics (Spurr and Barnes, 1973; Bond and Keeley, 2005). Any consideration of forests under a changing climate regime, therefore, must be viewed through a prism of fire interactions. Notwithstanding the importance of understanding how fire interacts with climate and imparts forest change, fire has been inadequately addressed in past assessments of climate impacts (National Assessment Synthesis Team, 2001). The recent interest in fire and climate has been fueled by growing scientific consensus that, across much of the US, wildfires are likely to become larger, more intense, and increasingly difficult to contain with climate change (Brown et al., 2004; Westerling and Bryant, 2008; Krawchuk et al., 2009; Littell et al., 2009; Littell et al., 2010; National Research Council, 2011; Westerling et al., 2011a,b). The increase in intense fires is a phenomenon that is evident throughout the world (Lohman et al., 2007; Attiwill and Binkley, 2013); but, is particularly apparent in the western US, where an increase in large fires appeared markedly in the mid 1980s coincident with increased spring and summer temperatures and earlier snow melt (Westerling et al., 2006). The last two decades have continued to see record wildfire seasons and escalating fire suppression costs (data from National Interagency Fire Center). Society’s ability to respond to climate change, mitigate negative consequences when possible, and adapt to those impacts that we are unable or unwilling to change will depend on a better understanding of the complex relationships between fire, vegetation and climate.

Schliep, E.M., Qi Dong, T., Gelfand, A.E. and Li, F. 2014. Modeling individual tree growth by fusing diameter tape and increment core data. Envrionmetrics. 25(8):610-620. (DOI: 10.1002/env.2324)

Abstract
Tree growth estimation is a challenging task as difficulties associated with data collection and inference often result in inaccurate estimates. Two main methods for tree growth estimation are diameter tape measurements and increment cores. The former involves repeatedly measuring tree diameters with a cloth or metal tape whose scale has been adjusted to give diameter readings directly. This approach has the advantage that diameters can be measured rapidly. However, because of the substantial error involved during tape measurements, negative diameter increments are often observed. Alternatively, annual radius increment data can be obtained by taking tree cores and averaging repeated measurements of the ring widths. Acquiring and analyzing tree cores is a time-consuming process, and taking multiple cores may have adverse effects on tree health. Therefore, radius increment data are typically only available for a subset of trees within a stand. We offer a fusion of the data sources, which enables us to accommodate missingness and to borrow strength across individuals. It enables individual tree-level inference as well as average or stand level inference. Our model recognizes that tree growth in a given year depends upon tree size at the start of the year as well as levels of appropriate covariates operating in that year. We apply our modeling to a fairly large dataset taken from two forest stands at Coweeta Hydrologic Laboratory in the southern Appalachians collected from 1991 to 2011.

Segura, C., Caldwell, P., Sun, G., McNulty, S. and Zhang, Y. 2014. A model to predict stream water temperature across the conterminous USA. Hydrological Processes. (DOI: 10.1002/hyp.10357)

Abstract
Stream water temperature (ts) is a critical water quality parameter for aquatic ecosystems. However, ts records are sparse or nonexistent in many river systems. In this work, we present an empirical model to predict ts at the site scale across the USA. The model, derived using data from 171 reference sites selected from the Geospatial Attributes of Gages for Evaluating Streamflow database, describes the linear relationship between monthly mean air temperature (ta) and ts. Multiple linear regression models are used to predict the slope (m) and intercept (b) of the ta–ts linear relation as a function of climatic, hydrologic and land cover characteristics. Model performance to predict ts resulted in a mean Nash-Sutcliffe efficiency coefficient of 0.78 across all sites. Application of the model to predict ts at additional 89 nonreference sites with a higher human alteration yielded a mean Nash-Sutcliffe value of 0.45. We also analysed seasonal thermal sensitivity (m) and found strong hysteresis in the ta–ts relation. Drainage area exerts a strong control on m in all seasons, whereas the cooling effect of groundwater was only evident for the spring and fall seasons. However, groundwater contributions are negatively related to mean ts in all seasons. Finally, we found that elevation and mean basin slope are negatively related to mean ts in all seasons, indicating that steep basins tend to stay cooler because of shorter residence times to gain heat from their surroundings. This model can potentially be used to predict climate change impacts on ts across the USA.

Sulman, B.N., Phillips, R.P., Oishi, A.C., Shevliakova, E. and Pacala, S.W. 2014. Microbe-driven turnover offsets mineral-mediated storage of soil carbon under elevated CO2. Nature Climate Change. 4:1099-1102. (DOI: Doi: 10.1038/NCLIMATE2436)

Abstract
The sensitivity of soil organic carbon (SOC) to changing environmental conditions represents a critical uncertainty in coupled carbon cycle-climate models. Much of this uncertainty arises from our limited understanding of the extent to which root-microbe interactions induce SOC losses (through accelerated decomposition or 'priming') or indirectly promote SOC gains (via 'protection' through interactions with mineral particles). We developed a new SOC model to examine priming and protection responses to rising atmospheric CO2. The model captured disparate SOC responses at two temperate free-air CO2 enrichment (FACE) experiments. We show that stabilization of 'new' carbon in protected SOC pools may equal or exceed microbial priming of 'old' SOC in ecosystems with readily decomposable litter and high clay content (for example, Oak Ridge). In contrast, carbon losses induced through priming dominate the net SOC response in ecosystems with more resistant litters and lower clay content (for example, Duke). The SOC model was fully integrated into a global terrestrial carbon cycle model to run global simulations of elevated CO2 effects. Although protected carbon provides an important constraint on priming effects, priming nonetheless reduced SOC storage in the majority of terrestrial areas, partially counterbalancing SOC gains from enhanced ecosystem productivity.

Vercoe, R., Welch-Devine, M., Hardy, R., Demoss, J., Bonney, S., Allen, K., Brosius, J.P., Charles, D., Crawford, B., Heisel, S., Heynen, N., de Jesús-Crespo, R., Nibbelink, N.P., Parker, L., Pringle, C., Shaw, A. and Van Sant, L. 2014. Acknowledging Trade-offs and Understanding Complexity: Exurbanization Issues in Macon County, North Carolina. Ecology and Society. 19(1):http://dx.doi.org/10.5751/ES-05970-190123.

Abstract
e applied an integrative framework to illuminate and discuss the complexities of exurbanization in Macon County, North Carolina. The case of Macon County, North Carolina, highlights the complexity involved in addressing issues of exurbanization in the Southern Appalachian region. Exurbanization, the process by which urban residents move into rural areas in search of unique natural amenities and idealized lifestyles, can often have a dramatic impact on the local economy, culture, and environment. Within Macon County, complex debates and tensions among multiple stakeholders struggle to address local residential development. How can better problem definition benefit rural communities in addressing exurbanization pressures and effects? We asserted that a key factor in the shortcomings of previous solutions was the shortsightedness inherent in policy that attempts to treat individual symptoms without being able to adequately characterize the underlying problem. The goal of the integrative framework is to initiate an iterative process of transparent negotiation, which recognizes a range of potential choices to be considered and to embrace the social complexities that can at times overwhelm scholars and practitioners, inviting simplification and polarization of the issues. This new and emerging framework offers a novel way of approaching conservation and development issues where other frameworks have failed. It helps acknowledge the difficult choices, i.e., trade-offs, that have to be made in a material process like exurbanization. Trade-offs will be necessary in any negotiation related to conservation. Therefore, conflict surrounding specific values, e.g., cultural, financial, or ecological, must be acknowledged upfront to move deeper into issues of plurality. Given the complexity, understanding how the process of exurbanization is being played out within Macon County provided not only an opportunity to demonstrate the functionality of an ntegrative approach, but also a call for further study of exurbanization dynamics.

Vose, J.M., Miniat, C.F., Sun, G. and Caldwell, P.V. 2014. Potential implications for expansion of freeze-tolerant Eucalyptus plantations on water resources in the southern United States. Forest Science. (DOI: http://dx.doi.org/10.5849/forsci.14-087)

Abstract
The potential expansion of freeze-tolerant (FT) Eucalyptus plantations in the United States has raised concerns about the implications for water resources. Modeling was used to examine the potential effects of expanding the distribution of FT Eucalyptus plantations in US Department of Agriculture Plant Hardiness Zones 8b and greater on water yield (Q). Analyses focused on two scales: the stand scale and the regional scale at the 12-digit Hydrologic Unit Code (HUC) watershed. Results suggested that the stand-level implications of planting FT Eucalyptus on Q could vary by location, the land cover type before Eucalyptus establishment, and the hydrologic conditions of the planting site and surrounding area. Compared with that for some pine plantations, Q at the stand level could be equal to or reduced by as much as to 130 mm year-1 (a reduction of 9–16% of precipitation) near the end of the rotation or on sites when leaf area index (LAI) is 4 m2 m-2 and reduced by as much as 500 mm year-1 (a reduction of 33–63% of precipitation) when LAI is 5 m2 m-2. In contrast, at the scale of conversion indicated by an economic analysis as most likely (e.g., <20% conversion of conifer to FT eucalyptus), reductions on Q at the 12-digit HUC scale will be negligible.

Warren, Robert J. II, Itamar Giladi and Mark A. Bradford, 2014. Competition as a Mechanism Structuring Mutualisms. Journal of Ecology 102:486-495

Abstract
1. Hutchinsonian niche theory posits that organisms have fundamental abiotic resource requirements from which they are limited by competition. Organisms also have fundamental biotic requirements, such as mutualists, for which they also might compete. 2. We test this idea with a widespread ant–plant mutualism. Ant-mediated seed dispersal (myrmecochory) in eastern North America involves a few ant species that can effectively disperse the seeds of many plant species. This imbalance suggests that ant-dispersed plants (myrmecochores) might compete for ant dispersers. We hypothesized that, because larger seeds are more attractive to ants, myrmecochores might segregate the timing of seed release by size to relieve competition. 3. Comparative literature analysis across plant species reveals that myrmecochore seed size increases with the fruiting season in a staggered pattern so that small- and large-seeded co-occurring species do not release seeds at the same time – a pattern not observed in plants using other dispersal modes. 4. We then presented foraging ants with small and large seeds in field trials throughout the fruiting season to test whether the observed temporal segregation in myrmecochore seed size is consistent with plant competition for ant dispersers. 5. Our results show that dispersal rates for smaller seeds increase across the growing season, but only in the absence of large seeds. Our combined literature and field data suggest that myrmecochores stagger fruiting by seed size so that small seeds are set earlier to avoid competition for dispersal mutualists with larger seeds. 6. Synthesis. Ecological interactions are often treated as either positive or negative, but our data blur this distinction by revealing that a positive interaction (mutualism) might be structured by a negative interaction (competition). Moreover, the recognition of biotic resources as critical niche requirements blurs the classic dichotomy between the fundamental (abiotic) versus realized (biotic limited) niche.

Welch-Devine, M., Hardy, R., Brosius, J. and Heynen, N. 2014. A pedagogical model for integrative training in conservation and sustainability. Ecology and Society. 19(2):10. http://dx.doi.org/10.5751/ES-06197-190210

Abstract
The benefits and challenges of interdisciplinary training are well documented, and several reviews have discussed the particular importance of interdisciplinary training for conservation scholars and practitioners. We discuss the progress within one university program to implement specific training models, elements, and tools designed to move beyond remaining barriers to graduate-level, interdisciplinary conservation education.

Wu, W., Clark, J.S., and J. Vose. 2014. Response of hydrology to climate change in the southern Appalachian Mountains using Bayesian inference. Hydrologic Processes, 28, 1616-1626.

Abstract
Predicting long-term consequences of climate change on hydrologic processes has been limited due to the needs to accommodate the uncertainties in hydrological measurements for calibration, and to account for the uncertainties in the models that would ingest those calibrations and uncertainties in climate predictions as basis for hydrological predictions. We implemented a hierarchical Bayesian (HB) analysis to coherently admit multiple data sources and uncertainties including data inputs, parameters, and model structures to identify the potential consequences of climate change on soilmoisture and streamflow at the headwatersheds ranging from lowto high elevations in the southern Appalachian region of the United States. We have considered climate change scenarios based on three greenhouse gas emission scenarios of the Interovernmental Panel on Climate Change: A2, A1B, and B1 emission scenarios. Full predictive distributions based on HB models are capable of providing rich information and facilitating the summarization of prediction uncertainties. With predictive uncertainties taken into account, themost pronounced change in soilmoisture and streamflow would occur under the A2 scenario at both low and high elevations, followed by the A1B scenario and then by the B1 scenario. Uncertainty in the change of soil moisture is less than that of streamflow for each season, especially at high elevations. A reduction of soil moisture in summer and fall, a reduction or slight increase of streamflow in summer, and an increase of streamflow in winter are predicted for all three scenarios at both low and high elevations. The hydrological predictions with quantified uncertainties from a HB model could aid more-informed water resource management in developing mitigation plans and dealing with water security under climate change.

Wurzburger, N. and Miniat, C.F. 2014. Drought enhances symbiotic dinitrogen fixation and competitive ability of a temperate forest tree. Oecologia. 174:1117-1126. (DOI: 10.1007/s00442-013-2851-0)

Abstract
General circulation models project more intense and frequent droughts over the next century, but many questions remain about how terrestrial ecosystems will respond. Of particular importance, is to understand how drought will alter the species composition of regenerating temperate forests wherein symbiotic dinitrogen (N2)-fixing plants play a critical role. In experimental mesocosms we manipulated soil moisture to study the effect of drought on the physiology, growth and competitive interactions of four co-occurring North American tree species, one of which (Robinia pseudoacacia) is a symbiotic N2-fixer. We hypothesized that drought would reduce growth by decreasing stomatal conductance, hydraulic conductance and increasing the water use efficiency of species with larger diameter xylem vessel elements (Quercus rubra, R. pseudoacacia) relative to those with smaller elements (Acer rubrum and Liriodendron tulipifera). We further hypothesized that N2 fixation by R. pseudoacacia would decline with drought, reducing its competitive ability. Under drought, growth declined across all species; but, growth and physiological responses did not correspond to species' hydraulic architecture. Drought triggered an 80% increase in nodule biomass and N accrual for R. pseudoacacia, improving its growth relative to other species. These results suggest that drought intensified soil N deficiency and that R. pseudoacacia's ability to fix N2 facilitated competition with non-fixing species when both water and N were limiting. Under scenarios of moderate drought, N2 fixation may alleviate the N constraints resulting from low soil moisture and improve competitive ability of N2-fixing species, and as a result, supply more new N to the ecosystem.

Yanai R. D., Tokuchi N., Campbell J. L., Green M. B., Matsuzaki E., Laseter S. N., Brown C. L., Bailey A. S., Lyons P., Levine C. R., Buso D. C., Likens G. E., Knoepp J. D. and Fukushima K. (2014), Sources of uncertainty in estimating stream solute export from headwater catchments at three sites, Hydrological Processes, DOI: 10.1002/hyp.10265

Abstract
Uncertainty in the estimation of hydrologic export of solutes has never been fully evaluated at the scale of a small-watershed ecosystem. We used data from the Gomadansan Experimental Forest, Japan, Hubbard Brook Experimental Forest, USA, and Coweeta Hydrologic Laboratory, USA, to evaluate many sources of uncertainty, including the precision and accuracy of measurements, selection of models, and spatial and temporal variation. Uncertainty in the analysis of stream chemistry samples was generally small but could be large in relative terms for solutes near detection limits, as is common for ammonium and phosphate in forested catchments. Instantaneous flow deviated from the theoretical curve relating height to discharge by up to 10% at Hubbard Brook, but the resulting corrections to the theoretical curve generally amounted to <0.5% of annual flows. Calibrations were limited to low flows; uncertainties at high flows were not evaluated because of the difficulties in performing calibrations during events. However, high flows likely contribute more uncertainty to annual flows because of the greater volume of water that is exported during these events. Uncertainty in catchment area was as much as 5%, based on a comparison of digital elevation maps with ground surveys. Three different interpolation methods are used at the three sites to combine periodic chemistry samples with streamflow to calculate fluxes. The three methods differed by <5% in annual export calculations for calcium, but up to 12% for nitrate exports, when applied to a stream at Hubbard Brook for 1997–2008; nitrate has higher weekly variation at this site. Natural variation was larger than most other sources of uncertainty. Specifically, coefficients of variation across streams or across years, within site, for runoff and weighted annual concentrations of calcium, magnesium, potassium, sodium, sulphate, chloride, and silicate ranged from 5 to 50% and were even higher for nitrate. Uncertainty analysis can be used to guide efforts to improve confidence in estimated stream fluxes and also to optimize design of monitoring programmes.

Zhu, K, C. W. Woodall, S. Ghosh, A. E. Gelfand, and J. S. Clark. 2014. Dual impacts of climate change: forest migration and turnover through life history. Global Change Biology, 20:251-264.

Abstract
Tree species are predicted to track future climate by shifting their geographic distributions, but climate-mediated migrations are not apparent in a recent continental-scale analysis. To better understand the mechanisms of a possible migration lag, we analyzed relative recruitment patterns by comparing juvenile and adult tree abundances in climate space. One would expect relative recruitment to be higher in cold and dry climates as a result of tree migration with juveniles located further poleward than adults. Alternatively, relative recruitment could be higher in warm and wet climates as a result of higher tree population turnover with increased temperature and precipitation. Using the USDA Forest Service’s Forest Inventory and Analysis data at regional scales, we jointly modeled juvenile and adult abundance distributions for 65 tree species in climate space of the eastern United States. We directly compared the optimal climate conditions for juveniles and adults, identified the climates where each species has high relative recruitment, and synthesized relative recruitment patterns across species. Results suggest that for 77% and 83% of the tree species, juveniles have higher optimal temperature and optimal precipitation, respectively, than adults. Across species, the relative recruitment pattern is dominated by relatively more abundant juveniles than adults in warm and wet climates. These different abundance-climate responses through life history are consistent with faster population turnover and inconsistent with the geographic trend of large-scale tree migration. Taken together, this juvenile–adult analysis suggests that tree species might respond to climate change by having faster turnover as dynamics accelerate with longer growing seasons and higher temperatures, before there is evidence of poleward migration at biogeographic scales.

Anderson, D.P., Turner, M.G., Pearson, S.M., Albright, T.P., Peet, R.K. and Wieben, A. 2013. Predicting Microstegium vimineum invasion in natural plant communities of the southern Blue Ridge Mountains, USA. Biological Invasions. 15(6):1217-1230. (DOI: 10.1007/s10530-012-0361-3)

Abstract
Shade-tolerant non-native invasive plant species may make deep incursions into natural plant communities, but detecting such species is challenging because occurrences are often sparse. We developed Bayesian models of the distribution of Microstegium vimineum in natural plant communities of the southern Blue Ridge Mountains, USA to address three objectives: (1) to assess local and landscape factors that influence the probability of presence of M. vimineum; (2) to quantify the spatial covariance error structure in occurrence that was not accounted for by the environmental variables; and (3) to synthesize our results with previous findings to make inference on the spatial attributes of the invasion process. Natural plant communities surrounded by areas with high human activity and low forest cover were at highest risk of M. vimineum invasion. The probability of M. vimineum presence also increased with increasing native species richness and soil pH, and decreasing basal area of ericaceous shrubs. After accounting for environmental covariates, evaluation of the spatial covariance error structure revealed that M. vimineum is invading the landscape by a hierarchical process. Infrequent long distance dispersal events result in new nascent subpopulations that then spread via intermediate- and short-distance dispersal, resulting in 3-km spatial aggregation pattern of sub-populations. Containment or minimisation of its impact on native plant communities will be contingent on understanding how M. vimineum can be prevented from colonizing new suitable habitats. The hierarchical invasion process proposed here provides a framework to organise and focus research and management efforts.

Anglin, Zachard W., Grossman, Gary D. 2013. Microhabitat use by southern brook trout (Salvelinus fontinalis) in a headwater North Carolina stream. Ecology of Freshwater Fish 22(4):567-577. https://doi.org/10.1111/eff.12059.

Abstract
Brook trout are the one of the only Salvelinus species native to eastern North America and range from Canada to Georgia. Very little is known, however, about the ecology of the southern form of this species. We quantified microhabitat use of southern brook trout in Ball Creek NC, a third-order stream, during six seasonal samples (summer 2010, autumn 2010, spring 2011, summer 2011, autumn 2011 and spring 2012). In general, trout preferentially occupied deeper microhabitats with lower mean velocities and higher amounts of erosional substrata than were randomly available. Older trout (1+ and 2+) occupied deeper microhabitats with lower mean velocities than yearling trout. These microhabitats typically represent ‘plunge pools’. Southern brook trout also occupied focal point velocities that were statistically indistinguishable from optimal velocities calculated for rainbow trout in the same system and thus may chose microhabitats that maximise net energy gain. Southern brook trout are found in isolated populations, and management strategies should focus on the preservation of plunge pool habitat for conservation of this subspecies.

Argerich, A., S.L. Johnson, S.D. Sebestyen, C.C. Rhoades, E. Greathouse, J.D. Knoepp, M.B. Adams, G.E. Likens, J.L. Campbell, W.H. McDowell, F.N. Scatena and G.G. Ice. Trends in stream nitrogen concentrations for forested reference catchments across the USA. 2013. Environmental Research Letters 8:014039 (8pp).

Abstract
To examine whether stream nitrogen concentrations in forested reference catchments have changed over time and if patterns were consistent across the USA, we synthesized up to 44 yr of data collected from 22 catchments at seven USDA Forest Service Experimental Forests. Trends in stream nitrogen presented high spatial variability both among catchments at a site and among sites across the USA. We found both increasing and decreasing trends in monthly flow-weighted stream nitrate and ammonium concentrations. At a subset of the catchments, we found that the length and period of analysis influenced whether trends were positive, negative or non-significant. Trends also differed among neighboring catchments within several Experimental Forests, suggesting the importance of catchment-specific factors in determining nutrient exports. Over the longest time periods, trends were more consistent among catchments within sites, although there are fewer long-term records for analysis. These findings highlight the critical value of long-term, uninterrupted stream chemistry monitoring at a network of sites across the USA to elucidate patterns of change in nutrient concentrations at minimally disturbed forested sites.

Block, C., Knoepp, J.D. and Fraterrigo, J.M. 2013. Interactive effects of disturbance and nitrogen availability on phosphorus dynamics of southern Appalachian forests. Biogeochemistry. 112:329-342. (DOI: 10.1007/s10533-012-9727-y)

Abstract
Understanding the main and interactive effects of chronically altered resource availability and disturbance on phosphorus (P) availability is increasingly important in light of the rapid pace at which human activities are altering these processes and potentially introducing P limitation. We measured P pools and fluxes in eighteen mixed forest stands at three elevations (low, mid, high) subjected to increasing atmospheric N deposition, where hemlock (Tsuga canadensis) was absent or declining due to infestation by the exotic hemlock woolly adelgid (Adelges tsugae). While total soil P was similar across the study area, phosphorus fractionation revealed distinct differences in the distribution of soil P fractions as elevation and N availability increased. Soils from high elevation plots where N availability was greatest had 139 % larger organic P pools and 55 % smaller residual and refractory P pools than soils from low elevation plots with less N availability, suggesting that increased N availability has driven the depletion of recalcitrant P pools by stimulating biotic demand and sequestration. These differences in P distribution among fractions influenced how tree mortality affected P dynamics. At high elevations, plots containing declining hemlocks had significantly greater foliar P concentrations and fluxes of P from the forest floor than reference plots at similar elevations, whereas at low and mid-elevations there were no consistent differences between plots. Across all elevation classes, hardwood foliar N:P ratios were lower in plots with declining hemlocks. Collectively, these results suggest that increased N availability enhances bioavailable P, which is sequestered in vegetation until disturbances liberate it.

Bradford, Mark A., Ashley D. Keiser, Christian A. Davies, Calley A. Mersmann and Michael S. Strickland. 2013. Empirical evidence that soil carbon formation from plant inputs is positively related to microbial growth. Biogeochemistry 113: 271-281.

Abstract
Plant-carbon inputs to soils in the form of dissolved sugars, organic acids and amino acids fuel much of heterotrophic microbial activity belowground. Initial residence times of these compounds in the soil solution are on the order of hours, with microbial uptake a primary removal mechanism. Through microbial biosynthesis, the dissolved compounds become dominant precursors for formation of stable soil organic carbon. How the chemical class (e.g. sugar) of a dissolved compound influences stabilization in field soils is unknown and predictions from our understanding of microbial metabolism, turnover and identity are contradictory. We show that soil carbon formation, from chronic amendments of dissolved compounds to fertilized and unfertilized grasslands, is 2.4-times greater from a sugar than an amino acid. Formation rates are negatively correlated with respiration rates of the compounds, and positively correlated with their recovery in microbial biomass. These relationships suggest that the efficiency of microbial growth on a compound is positively related to formation rates of soil organic carbon. Fertilization does not alter these findings, but together nitrogen and phosphorus additions reduce soil carbon formation. Our results highlight the need to consider both nutrient enrichment and global-change induced shifts in the form of dissolved root inputs to soils to predict future soil carbon stocks and hence phenomena such as climate warming and food security to which these stock sizes are intimately tied.

Brantley, S.T., Miniat, C.F. and Vose, J.M. 2013. Future species composition will affect forest water use after loss of eastern hemlock from southern Appalachian forests. Ecological Applications. 23(4):777-790. (DOI: http://dx.doi.org/10.1890/12-0616.1)

Abstract
Infestation of eastern hemlock (Tsuga canadensis (L.) Carr.) with hemlock woolly adelgid (HWA, Adelges tsugae) has caused widespread mortality of this key canopy species throughout much of the southern Appalachian Mountains in the past decade. Because eastern hemlock is heavily concentrated in riparian habitats, maintains a dense canopy, and has an evergreen leaf habit, its loss is expected to have a major impact on forest processes, including transpiration (Et). Our goal was to estimate changes in stand-level Et since HWA infestation, and predict future effects of forest regeneration on forest Et in declining eastern hemlock stands where hemlock represented 50�“60% of forest basal area. We used a combination of community surveys, sap flux measurements, and empirical models relating sap flux-scaled leaf-level transpiration (EL) to climate to estimate the change in Et after hemlock mortality and forecast how forest Et will change in the future in response to eastern hemlock loss.From 2004 to 2011, eastern hemlock mortality reduced annual forest Et by 22% and reduced winter Et by 74%. As hemlock mortality increased, growth of deciduous tree species�”especially sweet birch (Betula lenta L.), red maple (Acer rubrum L.), yellow poplar (Liriodendron tulipifera L.), and the evergreen understory shrub rosebay rhododendron (Rhododendron maximum L.)�” also increased, and these species will probably dominate post-hemlock riparian forests. All of these species have higher daytime EL rates than hemlock, and replacement of hemlock with species that have less conservative transpiration rates will result in rapid recovery of annual stand Et. Further, we predict that annual stand Et will eventually surpass Et levels observed before hemlock was infested with HWA. This long-term increase in forest Et may eventually reduce stream discharge, especially during the growing season. However, the dominance of deciduous species in the canopy will result in a permanent reduction in winter Et and possible increase in winter stream discharge. The effects of hemlock die-off and replacement with deciduous species will have a significant impact on the hydrologic flux of forest transpiration, especially in winter. These results highlight the impact that invasive species can have on landscape-level ecosystem fluxes.

Bruce, R.C. 2013. Size-Mediated Tradeoffs in Life-History Traits in Dusky Salamanders. Copeia. (DOI: 10.1643/CE-12-120)

Abstract
Among salamanders of the genus Desmognathus, the larger species tend to be more aquatic and the smaller more terrestrial. I studied life histories in assemblages of Desmognathus in the southern Blue Ridge Mountains of North Carolina at sites in the Cowee and southern Nantahala Mountains. Traits evaluated included mortality/survival, age at first reproduction, fecundity, and body size. The first three are direct fitness traits that enter into the characteristic equation, x=aS�lxmxe2rx = 1.0. One assemblage (Wolf Creek), in the Cowee Mountains, comprises three species, from larger to smaller, D. quadramaculatus, D. monticola, and D. ocoee. A second assemblage (Coweeta Creek), in the Nantahala Mountains, also includes D. quadramaculatus, D. monticola, and D. ocoee, as well as the smaller D. aeneus and D. wrighti. I also studied three species only (D. ocoee, D. aeneus, D. wrighti) in an assemblage of six species (Nantahala River) in the Nantahala Mountains just west of Coweeta Creek. In these assemblages, age at first reproduction and fecundity are greater in the larger, more aquatic species. Instantaneous mortality rate is lower in the larger species; however, the latter have lower survival to first reproduction than the smaller species because developmental time to sexual maturation is lengthier than in the smaller species. Among species, it appears that size-mediated tradeoffs exist among age at sexual maturation, fecundity, and survival. The tradeoff relationships of life-history traits among species in both the Cowee and Nantahala assemblages may reflect fitness invariance or symmetry, perhaps stemming from design constraints in the genus Desmognathus. What remain unclear are factors contributing to the correlation between body size and the position of species along the stream-to-forest habitat gradient.

Campbell, P.K.E., Middleton, E.M., Thome, K.J., Kokaly, R.F., Huemmrich, K.F., Lagomasino, D., Novick, K.A. and Brunsell, N.A. 2013. Hyperion reflectance time series at calibration and validation sites: stability and sensitivity to seasonal dynamics. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 6(2):276-290. (DOI: 10.1109/JSTARS.2013.2246139)

Abstract
This study evaluated Earth Observing 1 (EO-1) Hyperion reflectance time series at established calibration sites to assess the instrument stability and suitability for monitoring vegetation functional parameters. Our analysis using three pseudo-invariant calibration sites in North America indicated that the reflectance time series are devoid of apparent spectral trends and their stability consistently is within 2.5-5 percent throughout most of the spectral range spanning the 12+ year data record. Using three vegetated sites instrumented with eddy covariance towers, the Hyperion reflectance time series were evaluated for their ability to determine important variables of ecosystem function. A number of narrowband and derivative vegetation indices (VI) closely described the seasonal profiles in vegetation function and ecosystem carbon exchange (e.g., net and gross ecosystem productivity) in three very different ecosystems, including a hardwood forest and tallgrass prairie in North America, and a Miombo woodland in Africa. Our results demonstrate the potential for scaling the carbon flux tower measurements to local and regional landscape levels. The VIs with stronger relationships to the CO2 parameters were derived using continuous reflectance spectra and included wavelengths associated with chlorophyll content and/or chlorophyll fluorescence. Since these indices cannot be calculated from broadband multispectral instrument data, the opportunity to exploit these spectrometer-based VIs in the future will depend on the launch of satellites such as EnMAP and HyspIRI. This study highlights the practical utility of space-borne spectrometers for characterization of the spectral stability and uniformity of the calibration sites in support of sensor cross-comparisons, and demonstrates the potential of narrowband VIs to track and spatially extend ecosystem functional status as well as carbon processes measured at flux towers.

Cheever, B.M., Webster, J.R., Bilger, E. and Thomas, S.A. 2013. The relative importance of exogenous and substrate derived nitrogen for microbial growth during leaf decomposition. Ecology. 94:1614-1625. (DOI: 10.1890/12-1339.1)

Abstract
Heterotrophic microbes colonizing detritus obtain nitrogen (N) for growth by assimilating N from their substrate or immobilizing exogenous inorganic N. Microbial use of these two pools has different implications for N cycling and organic matter decomposition in the face of the global increase in biologically available N. We used sugar maple leaves labeled with 15 N to differentiate between microbial N that had been assimilated from the leaf substrate (enriched with 15 N) or immobilized from the water (natural abundance 15 N: 14 N) in five Appalachian streams ranging in ambient NO 3 -N concentrations from about 5 to 900 l gNO 3 - N/L. Ambient NO 3 concentration increased sugar maple decomposition rate but did not influence the proportion of microbial N derived from substrate or exogenous pools. Instead, these proportions were strongly influenced by the percentage of detrital ash-free dry mass (AFDM) remaining. Substrate-derived N made up a large proportion of the microbial N after the first 24 h in all streams. Detrital and microbial isotopic 15 N signatures approached that of the water as decomposition progressed in all streams, suggesting that exogenous N may be the predominant source of N for meeting microbial requirements even when exogenous N concentrations are low. Our results support predictions of more rapid decomposition of organic matter in response to increased N availability and highlight the tight coupling of processes driving microbial N cycling and organic matter decomposition.

Clark, J.S., D. M Bell, M. Kwit, A. Powell, And K. Zhu. 2013. Dynamic inverse prediction and sensitivity analysis with high-dimensional responses: application to climate-change vulnerability of biodiversity. Journal of Biological, Environmental, and Agricultural Statistics, 18:376-404.

Abstract
Sensitivity analysis (SA) of environmental models is inefficient when there are large numbers of inputs and outputs and interactions cannot be directly linked to input variables. Traditional SA is based on coefficients relating the importance of an input to an output response, generating as many as one coefficient for each combination of model input and output. In many environmental models multiple outputs are part of an integrated response that should be considered synthetically, rather than by separate coefficients for each output. For example, there may be interactions between output variables that cannot be defined by standard interaction terms for input variables. We describe dynamic inverse prediction (DIP), a synthetic approach to SA that quantifies how inputs affect the combined (multivariate) output. We distinguish input interactions (specified as a traditional product of input variables) from output interactions (relationships between outputs not directly linked to inputs). Both contribute to traditional SA coefficients and DIP in ways that permit interpretation of unexpected model results. An application of broad and timely interest, anticipating effects of climate change on biodiversity, illustrates how DIP helps to quantify the important input variables and the role of interactions. Climate affects individual trees in competition with neighboring trees, but interest lies at the scale of species and landscapes. Responses of individuals to climate and competition for resources involve a number of output variables, such as birth rates, growth, and mortality. They are all components of ‘individual health’, and they interact in ways that cannot be linked to observed inputs, through allocation constraints.We show how prior dependence is introduced to aid interpretation of inputs in the context of ecological resource modeling. We further demonstrate that a new approach to multiplicity (multiple-testing) correction can be implemented in such models to filter through the large number of input combinations. DIP provides a synthetic index of important inputs, including climate vulnerability in the context of competition for light and soil moisture, based on the full (multivariate) response. By aggregating in specific ways (over individuals, years, and other input variables) we provide ways to summarize and rank species in terms of their vulnerability to climate change. This article has supplementary material online.

Conor Keitzer, S. and Goforth, R. R. (2013), Salamander diversity alters stream macroinvertebrate community structure. Freshw Biol, 58: 2114–2125. doi:10.1111/fwb.12195

Abstract
1. Salamanders are abundant consumers in many fishless stream ecosystems, but few studies have explicitly examined their ecological role. Stream-dwelling salamander larvae are generalist predators of aquatic macroinvertebrates and may play an important role in structuring macroinvertebrate communities. The potential for emergent effects of multiple predator species suggests that changes in salamander diversity could alter their effects on macroinvertebrate communities, but this has not been tested. 2. We used in-stream enclosures to manipulate the presence and diversity of the two most abundant salamanders, Eurycea wilderae (EWIL) and Desmognathus quadramaculatus (DQUA), in a southern Appalachian Mountain headwater stream to examine the impacts of salamander predation on macroinvertebrate communities. We were particularly interested in testing for potential diversity effects by comparing the effects of each species in monoculture to polycultures of both species (BOTH). 3. Salamanders reduced macroinvertebrate abundance compared to the control treatment (CONTROL), but only when both species were present together. The general pattern of macroinvertebrate abundance among treatments was: CONTROL = EWIL = DQUA > BOTH, although no treatment significantly reduced the abundance of epibenthic taxa. The BOTH treatment also significantly altered macroinvertebrate community structure and reduced taxon richness by c. 57%. The effects of salamanders were particularly pronounced for chironomids (Diptera: Chironomidae), which comprised the majority of macroinvertebrate total abundance. 4. Increased salamander diversity substantially altered macroinvertebrate communities, suggesting that niche complementarity or facilitation occurred despite the apparent functional similarity of these two species. Therefore, changes in salamander diversity may alter the effects of salamander communities on macroinvertebrates, which may cascade through food webs to affect stream ecosystem function.

Coughlan, Michael R. 2013. Errakina: Pastoral Fire Use and Landscape Memory in the Basque Region of the French Western Pyrenees. Journal of Ethnobiology 33(1): 86-104.

Abstract
People in the French Western Pyrenees have used fire for millennia in order to shape and manage landscapes. This history has left cultural and ecological legacies that both reflect and ensure the relative persistence of landscape patterns and processes. In this paper I draw on ethnographic research, ethnohistorical evidence, and Bayesian spatial analyses of historical fire use locations and land use maps to shed some light on human-firelandscape dynamics in the Pyrenees for the years 1830 to 2011. I show how cultural and ecological legacies reflect a self-organized fire management regime that emerges from fire use driven by the production goals of individual households. I frame the self-organizing dynamic inherent in Pyrenean pastoral fire use as ‘‘landscape memory.’’ This conclusion has implications for the future direction of fire-related conservation policy for the Pyrenees and for analogous systems characterized by self-organized land management regimes.

Coughlan, Michael R. 2013. Farmers, flames, and forests: Historical ecology of pastoral fire use and landscape change in the French Western Pyrenees, 1830-2011. Forest Ecology and Management.

Abstract
The human use of fire is a major disturbance factor shaping the long term composition and patterning of temperate forest landscapes. Yet, knowledge of the role of human agency in the historical dynamics of fire in temperate forests remains vague. This paper presents a cross-scale Bayesian Weights of Evidence analysis of change in the spatial patterns of fire use over the last 180 years for a village territory in the Basque portion of the French Pyrenees. Research investigated the historical relationships between social institutions that control land use, the spatial patterning of fire use, and landscape change. Analysis considered the spatial contexts within which humans use and manage land: the household institution and the parcel unit of land management. Bayesian methods established statistically significant associations between social and ecological factors driving fire use and landscape change. These associations suggest that social institutions differentially affected fire use patterns through inherited constraints. The resulting socioecological legacies helped to explain the spatial patterns of landscape change. Uncertainty highlighted in the modeling process suggests that we need a better understanding of the historical ecological dynamics of household institutions and land use change in order to better explain relationships between variability in land use intensity and the fire regime.

Coughlan, Michael R. 2013. Unauthorized Firesetting as Socioecological Disturbance: A Spatiotemporal Analysis of Incendiary Wildfires in Georgia, USA, 1987-2010. Fire Ecology 9(3): 45-63.

Abstract
I analyzed the spatiotemporal patterning of intentional, unauthorized landscape fires in the state of Georgia, USA, for the years 1987 through 2010 with the aim of delineating socioecological constraints on and firesetter preferences for the timing and placement of ignitions. Unauthorized fires represent complex phenomena through which actors compete over social and ecological outcomes that transcend the spatiotemporal confines of individual fires themselves. Current classificatory systems define unauthorized firesetting behavior as irrational, destructive, and malicious. Because landscape fires cause both positive and negative consequences for biological diversity and ecosystems services, perceived costs and benefits of fires are contestable and relative to point of view. The locational and temporal patterns of unauthorized landscape fires examined in this study do not show firesetter preferences for maximizing damage to landscapes. Instead, unauthorized fires in Georgia potentially contribute to the maintenance of landscapes adapted to frequent, dormant- and early growing-season fire regimes.

Elliott, Katherine J., Jennifer D. Knoepp, James M. Vose, and William A. Jackson. Interacting effects of wildfire severity and liming on nutrient cycling in a southern Appalachian wilderness area. 2013. Plant and Soil 366:165-183.

Abstract
Aims Wilderness and other natural areas are threatened by large-scale disturbances (e.g., wildfire), air pollution, climate change, exotic diseases or pests, and a combination of these stress factors (i.e., stress complexes). Linville Gorge Wilderness (LGW) is one example of a high elevation wilderness in the southern Appalachian region that has been subject to stress complexes including chronic acidic deposition and several wildfires, varying in intensity and extent. Soils in LGW are inherently acidic with low base cation concentrations and decades of acidic deposition have contributed to low pH, based saturation, and Ca:Al ratio. We hypothesized that wildfires that occurred in LGW followed by liming burned areas would accelerate the restoration of acidic, nutrient depleted soils. Because soils at LGW had extremely low concentrations of exchangeable Ca2+ and Mg2+ dolomitic lime was applied to further boost these cations. We evaluated the effectiveness of dolomitic lime application in restoring exchangeable Ca2+ and Mg2+ and subsequently increasing pH and Ca:Al ratio of soils and making Ca and Mg available to recovering vegetation.

Gustafson, S., Heynen, N., Rice, J.L., Gragson, T., Shepherd, J.M., and Strother, C. (2014). Megapolitan political ecology and urban metabolism in southern Appalachia. The Professional Geographer. (DOI:10.1080/00330124.2014.905158)

Abstract
Drawing on megapolitan geographies, urban political ecology, and urban metabolism as theoretical frameworks, this paper theoretically and empirically explores ‘megapolitan political ecology.’ First, we elucidate a theoretical framework in the context of southern Appalachia and, in particular, the Piedmont megapolitan region. We argue that the megapolitan region is a useful scale through which to understand urban metabolic connections that constitute this rapidly urbanizing area. We also push the environmental history and geography literature of the US South and southern Appalachia to consider the central role urban metabolic connections play in the region’s pressing social and environmental crises. Secondly, we empirically illuminate these human and non-human urban metabolisms across the Piedmont megapolitan region using data from the Coweeta Long-Term Ecological Research program. We especially highlight here a growing ‘Ring of Asphalt’ that epitomizes several developing changes to patterns of metabolism. We conclude by suggesting that these Coweeta LTER data show that changing urban metabolism, ranging from flows of people to flows of water, poses a complicated problem for regional governance and vitality in the future.

J.S. Norman, J.E. Barrett. 2013. Substrate and nutrient limitation of ammonia-oxidizing bacteria and archaea in temperate forest soil. Soil Biology & Biochemistry 69:141-146.

Abstract
Ammonia-oxidizing microbes control the rate-limiting step of nitrification, a critical ecosystem process, which affects retention and mobility of nitrogen in soil ecosystems. This study investigated substrate (NH4þ) and nutrient (K and P) limitation of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in temperate forest soils at Coweeta Hydrologic Laboratory, a long-term ecological research site in western North Carolina, USA. We investigated substrate and nutrient limitation by amending soils with either ammonium or a nutrient solution containing P and K, then assessing the growth of these organisms during in situ soil incubations. We found substantial growth of both AOA and AOB during all incubations including unamended control incubations. Our results demonstrate that substrate availability limits nitrification by AOB and that high levels of substrate addition inhibit the growth of AOA in these soils. We found no evidence for nutrient limitation of AOB, though nutrient addition indirectly stimulated nitrification by AOB through increased nitrogen mineralization. Our data did suggest nutrient limitation by AOA, though it is unclear whether AOA significantly contribute to ammonia oxidation in this system. Furthermore, we show that AOB are responsible for the majority of ammonia oxidation in high substrate, high nutrient conditions.

Jackson, M.M., Pearson, S.M. and Turner, M.G. 2013. Performance and population dynamics of a native understory herb differ between young and old forest stands in the Southern Appalachians. Forest Ecology and Management. 304:444-454. (DOI: 10.1016/j.foreco.2013.05.049)

Abstract
Anthropogenic disturbances (e.g., logging) can strongly affect the composition and structure of forest understory herb communities, with land-use legacies often persisting for decades or even centuries. Many studies of forest plant response to land-use history have focused on species distributions and abundances, and argued broadly for either dispersal or establishment limitation as biological mechanisms for slow recolonization. We asked how performance and population dynamics of the temperate forest herb Prosartes lanuginosa differed between recently logged (20�“40 years ago) and old (>90 years) logged forests in the Southern Appalachians, USA. All stands were well developed with canopy closure ranging from 59�“90%. Performance of individual plants (N = 859) was monitored over three years across 19 forest stands (N = 9 recent and 10 old). We also conducted a seed sowing experiment to determine whether germination and establishment differed with stand age. Stage-based matrix models and life table response experiments (LTREs) were used to quantify the contributions of each life-history transition to observed differences in population growth rates (λ) across stands and between years. Field measurements revealed that population growth rates were higher in older logged stands (λ = 0.78�“0.84) than in more recently logged stands (λ = 0.68�“0.74), primarily because of reduced fecundity and reduced recruitment from vegetative to flowering life stages. Seed germination and seedling survival did not differ between old and young logged forests. Across stands, population growth rates were higher during the first annual transition than the second, which followed a drought spring. However, the mechanisms for these differences in λ varied with stand age; populations in old forests responded to drought conditions by lowering fecundity, whereas populations in young forests responded with lower recruitment from vegetative to flowering stages. Our results showed that logging history affects plant performance beyond the establishment phase and interacts with environmental conditions to influence population dynamics. Our results also emphasize the need for multiple performance measures to assess the effects of land-use history on forest plants.

Johnson, L.T., Tank, J.L., Hall, R.O., Mulholland, P.J., Hamilton, S., Valett, H.M., Webster, J.R., Arango, C.P., Beaulieu, J.J., Bernot, M.J., Burgin, A.J., McDowell, W., Peterson, B.J. and Thomas, S.A. 2013. In-stream dissolved organic nitrogen production in headwater streams. Limnology and Oceanography. Limnology and Oceanography. 58:1271-1285. (DOI: 10.4319/lo.2013.58.4.1271)

Abstract
Most nitrogen (N) assimilation in lake and marine ecosystems is often subsequently released via autochthonous dissolved organic nitrogen (DON) production, but autochthonous DON production has yet to be quantified in flowing waters. We measured in-stream DON production following 24 h 15 N-nitrate (NO { 3 ) tracer additions in 36 headwater streams, a subset of sites from the second Lotic Intersite Nitrogen eXperiment. Streams were located in five North American ecoregions and drained basins dominated by native vegetation, agriculture, or urban land use. Using a two-compartment model, we could quantify DON production in 15 streams as a function of DO 15 N derived from 15 N tracer in biomass compartments. The streams with detectable DON production had higher % modified land use (agriculture + urban) in their basins than did streams with undetectable DON production. Median DON production represented 8 % of total NO { 3 uptake when we used N biomass estimates based on N assimilated over 1 d (measured directly from the 15 N additions). Median DON production was 17 % of total NO { 3 uptake when we used N assimilated over 42 d (extrapolated from previous 15 N tracer studies). Variation in DON production was positively correlated with ecosystem respiration, indicating that stream heterotrophy may influence DON production. In-stream DON production was similar in magnitude to stream denitrification and nitrification, indicating that the production of autochthonous DON can represent a substantial transformation of stream N. Our results confirm that headwater streams can quickly convert inorganic N into organic forms, although the ultimate fate of DON remains unclear.

Johnson, Laura T.; Tank, Jennifer L.; Hall Jr., Robert O.; Mullholland, Patrick J.; Hamilton, Stephen K.; Valett, H. Maurice; Webster, Jackson R.; Bernot, Melody J.; McDowell, William H.; Peterson, Bruce J.; Thomas, Suzanne M. 2013. Quantifying the production of dissolved organic nitrogen in headwater streams using 15N tracer additions. Limnology and Oceanography 58(4): 1271-1285. DOI: 10.4319/lo.2013.58.4.1271.

Abstract
Most nitrogen (N) assimilation in lake and marine ecosystems is often subsequently released via autochthonous dissolved organic nitrogen (DON) production, but autochthonous DON production has yet to be quantified in flowing waters. We measured in-stream DON production following 24 h 15N-nitrate (NO{ 3 ) tracer additions in 36 headwater streams, a subset of sites from the second Lotic Intersite Nitrogen eXperiment. Streams were located in five North American ecoregions and drained basins dominated by native vegetation, agriculture, or urban land use. Using a two-compartment model, we could quantify DON production in 15 streams as a function of DO15N derived from 15N tracer in biomass compartments. The streams with detectable DON production had higher % modified land use (agriculture + urban) in their basins than did streams with undetectable DON production. Median DON production represented 8% of total NO{ 3 uptake when we used N biomass estimates based on N assimilated over 1 d (measured directly from the 15N additions). Median DON production was 17% of total NO{ 3 uptake when we used N assimilated over 42 d (extrapolated from previous 15N tracer studies). Variation in DON production was positively correlated with ecosystem respiration, indicating that stream heterotrophy may influence DON production. In-stream DON production was similar in magnitude to stream denitrification and nitrification, indicating that the production of autochthonous DON can represent a substantial transformation of stream N. Our results confirm that headwater streams can quickly convert inorganic N into organic forms, although the ultimate fate of DON remains unclear.

Keiser, A., Knoepp, J.D. and Bradford, M. 2013. Microbial communities may modify how litter quality affects potential decomposition rates as tree species migrate. Plant and Soil. (DOI: 10.1007/s11104-013-1730-0)

Abstract
Background and aims Climate change alters regional plant species distributions, creating new combinations of litter species and soil communities. Biogeographic patterns in microbial communities relate to dissimilarity in microbial community function, meaning novel litters to communities may decompose differently than predicted from their chemical composition. Therefore, the effect of a litter species in the biogeochemical cycle of its current environment may not predict patterns after migration. Under a tree migration sequence we test whether litter quality alone drives litter decomposition, or whether soil communities modify quality effects. Methods Litter and soils were sampled across an elevation gradient of different overstory species where lower elevation species are predicted to migrate upslope. We use a common garden, laboratory microcosm design (soil community x litter environment) with single and mixed-species litters. Results We find significant litter quality and microbial community effects (P <0.001), explaining 47 % of the variation in decomposition for mixed-litters. Conclusion Soil community effects are driven by the functional breadth, or historical exposure, of the microbial communities, resulting in lower decomposition of litters inoculated with upslope communities. The litter x soil community interaction suggests that litter decomposition rates in forests of changing tree species composition will be a product of both litter quality and the recipient soil community.

Keitzer, S. Conor,Goforth, Reuben R. (2013) Spatial and seasonal variation in the ecological significance of nutrient recycling by larval salamanders in Appalachian headwater streams, Freshwater Science, 32:4, doi: 10.1899/13-002.1

Abstract
Salamanders are abundant consumers in many temperate streams and may be important recyclers of biologically essential nutrients, but their ecological role is poorly understood. The ecological significance of nutrient recycling by salamanders may vary spatially and seasonally because of their potentially patchy distribution in streams and the dynamic nature of stream hydrology and other nutrient fluxes. We examined the spatial and seasonal variation of salamander-driven nutrient recycling in 3 headwater streams in the southern Appalachian Mountains. We quantified the aggregate areal excretion rates of N (NH4+-N) for the larvae of the 2 most abundant salamander species in these steams before and after leaf fall to examine spatial and seasonal variation in the supply of nutrients from salamanders. We used short-term nutrient additions in each stream to examine temporal heterogeneity in the ecosystem demand for NH4+-N. Before leaf fall, salamanders were capable of meeting ,10% of the ecosystem demand for NH4+-N and could turn over the ambient nutrient pool in ,3 km. The significance of this contribution declined to ,3% after leaf fall and the turnover length increased 73. The ecological significance of salamander nutrient excretion varied by as much as 173 within streams and was as high as 30% of the nutrient demand in some stream sections, a result suggesting that salamanders may create biogeochemical hotspots in these nutrient-limited ecosystems. Thus, salamanders appear to be capable of contributing substantially to stream nutrient cycles through the excretion of limiting nutrients and may be underappreciated members of headwater stream ecosystems, particularly at small spatial scales. However, this contribution varied substantially seasonally and spatially.

King, Joshua R., Robert J. Warren, and Mark A. Bradford. 2013. Social Insects Dominate Eastern US Temperate Hardwood Forest Macroinvertebrate Communities in Warmer Regions. PLOS ONE 8(10):e75843.

Abstract
Earthworms, termites, and ants are common macroinvertebrates in terrestrial environments, although for most ecosystems data on their abundance and biomass is sparse. Quantifying their areal abundance is a critical first step in understanding their functional importance. We intensively sampled dead wood, litter, and soil in eastern US temperate hardwood forests at four sites, which span much of the latitudinal range of this ecosystem, to estimate the abundance and biomass m22 of individuals in macroinvertebrate communities. Macroinvertebrates, other than ants and termites, differed only slightly among sites in total abundance and biomass and they were similar in ordinal composition. Termites and ants were the most abundant macroinvertebrates in dead wood, and ants were the most abundant in litter and soil. Ant abundance and biomass m22 in the southernmost site (Florida) were among the highest values recorded for ants in any ecosystem. Ant and termite biomass and abundance varied greatly across the range, from ,1% of the total macroinvertebrate abundance (in the northern sites) to .95% in the southern sites. Our data reveal a pronounced shift to eusocial insect dominance with decreasing latitude in a temperate ecosystem. The extraordinarily high social insect relative abundance outside of the tropics lends support to existing data suggesting that ants, along with termites, are globally the most abundant soil macroinvertebrates, and surpass the majority of other terrestrial animal (vertebrate and invertebrate) groups in biomass m22. Our results provide a foundation for improving our understanding of the functional role of social insects in regulating ecosystem processes in temperate forest.

Kuhman, T.R., Pearson, S.M. and Turner, M.G. 2013. Why does land-use history facilitate non-native plant invasion? A field experiment with Celastrus orbiculatus in the southern Appalachians. Biological Invasions. 15(3):613-626. (DOI: 10.1007/s10530-012-0313-y)

Abstract
Although historic land use is often implicated in non-native plant invasion of forests, little is known about how land-use legacies might actually facilitate invasion. We conducted a 2-year field seeding experiment in western North Carolina, USA, to compare germination and first-year seedling survival of Celastrus orbiculatus Thunb. in stands that had been cultivated and abandoned a century earlier and were dominated by tulip poplar (Liriodendron tulipifera L.), and in paired stands that had never been cultivated and were dominated by oaks (Quercus spp.). Experiments were conducted at five sites with paired tulip poplar and oak stands by varying litter mass (none, low, or high) and litter type (tulip poplar or oak). We also performed reciprocal soil translocations using pots seeded with C. orbiculatus. Soil moisture and temperature were measured throughout the growing season. Germination and survival were highest in the tulip poplar stands. Germination was also higher in plots with low litter mass. Seedling survival was highest in plots with low litter mass or no litter. Soil moisture was higher in tulip poplar stands and under low-mass litter. Differences in germination and survival among the potted plants were minimal, suggesting that soil type and ambient site conditions were less important than litter conditions for C. orbiculatus establishment. Our results suggest that the low litter mass and mesic soil conditions that are characteristic of tulip poplar stands may confer higher invasibility and explain the higher abundance of C. orbiculatus in areas with successional overstory communities associated with historically cultivated forests.

Lumpkin, H.A. and Pearson, S.M. 2013. Effects of Exurban Development and Temperature on Bird Species in the Southern Appalachians. Conservation Biology. (DOI: 10.1111/cobi.12085)

Abstract
Land-use dynamics and climatic gradients have large effects on many terrestrial systems. Exurban development, one of the fastest growing forms of land use in the United States, may affect wildlife throughhabitat fragmentation and building presence may alter habitat quality. We studied the effects of residential development and temperature gradients on bird species occurrence at 140 study sites in the southernAppalachian Mountains (North Carolina, U.S.A.) that varied with respect to building density and elevation. We used occupancy models to determine 36 bird species’ associations with building density, forest canopy cover, average daily mean temperature, and an interaction between building density and mean temperature. Responses varied with habitat requirement, breeding range, and migration distance. Building density and mean temperature were both included in the top occupancy models for 19 of 36 species and a building density by temperature interaction was included in models for 8 bird species. As exurban development expands in the southern Appalachians, interior forest species and Neotropical migrants are likely to decline, but shrubland or edge species are not likely to benefit. Overall, effects of building density were greater than those of forest canopy cover. Exurban development had a greater effect on birds at high elevations due to a greater abundance of sensitive forest-interior species and Neotropical migrants. A warming climate may exacerbate these negativeeffects.

Lynsey Long, S. and Rhett Jackson, C. (2014), Variation of stream temperature among mesoscale habitats within stream reaches: southern Appalachians. Hydrol. Process., 28: 3041-3052. doi: 10.1002/hyp.9818

Abstract
Stream mesoscale habitats have systematic topographic relationships to hyporheic flow patterns, which may create predictable temperature variation between mesoscale habitat types. We investigated whether systematic differences in temperature metrics occurred between mesoscale habitats within reaches of small streams tributary to the upper Little Tennessee River, southern Appalachians. Surface water temperature was recorded over three or four mid-summer days in four mesoscale habitat types: riffle, main riffle, pool and alcove in 44 stream segments (sites). Temperature metrics were calculated for each mesoscale habitat relative to the mean value of the metric over the stream: Δ maximum temperature, Δ average maximum temperature and Δ maximum daily variation and also for each site: standard deviation of the maximum temperature and average diurnal variation (ADV). Sites were categorized as fully or partially forested. Pool tailouts had statistically significantly lower Δ maximum temperature and Δ average maximum temperature than riffle tailouts in partially forested sites, although differences were small. This was the opposite of what was expected in the presence of hyporheic exchange, indicating hyporheic exchange is not a dominant driver of mesoscale habitat temperatures at these sites. Temperature differences between mesoscale habitat units were small and unlikely to have ecological significance. We also evaluated relationships between stream temperature and riparian condition, watershed % impervious surfaces, watershed % non-forested and elevation. ADV and standard deviation of the maximum temperature were significantly higher in partially forested sites, indicating that partially forested sites have greater temperature ranges and spatial variation of maximum temperatures. ADV decreased with elevation and increased with % impervious surfaces.

Mayfield, M.M., Dwyer, J.M., Chalamandrier, L., Wells, J.A., Bonser, S.B., Catterall, C.P., DeClerck, F., Ding, Y., Fraterrigo, J.M., Metcalfe, D.J., Queiroz, C., Vesk, P.A. and Morgan, J.W. 2013. Differences in forest plant functional trait distributions across land-use and productivity gradients. American Journal of Botany. 100(7):1356-1368. (DOI: 10.3732/ajb.1200461)

Abstract
Premise of study: Plant functional traits are commonly used as proxies for plant responses to environmental challenges, yet fewstudies have explored how functional trait distributions differ across gradients of land-use change. By comparing trait distributionsin intact forests with those across land-use change gradients, we can improve our understanding of the ways land-usechange alters the diversity and functioning of plant communities.• Methods: We examined how the variation and distribution of trait values for seven plant functional traits differ between referencenatural forest and three types of land-use conversion (pasture, old-fi eld, or “legacy” sites�”regrowth following logging),landscape productivity (NPP) and vegetation strata (tree or non-tree “understory”), in a meta-analysis of studies from 15 landscapesacross fi ve continents.• Key results: Although trait variation often differed between land-uses within a landscape, these patterns were rarely consistentacross landscapes. The variance and distribution of traits were more likely to differ consistently between natural forest andland-use conversion categories for understory (non-tree) plants than for trees. Landscape productivity did not signifi cantly alterthe difference in trait variance between natural forest and land-use conversion categories for any trait except dispersal.• Conclusions: Our results suggest that even for traits well linked to plant environmental response strategies, broad classes ofland-use change and landscape productivity are not generally useful indicators of the mechanisms driving compositionalchanges in human-modifi ed forest systems

McDonnell, T., Sullivan, T., Cosby, B., Jackson, W. and Elliott, K. (2013) Effects of climate, land management, and sulfur deposition on soil base cation supply in National Forests of the southern Appalachian mountains. Water Air Soil Pollution. 224(1733).

Abstract
Forest soils having low exchangeable calcium (Ca) and other nutrient base cation (BC) reserves may induce nutrient deficiencies in acid-sensitive plants and impact commercially important tree species. Past and future depletion of soil BC in response to acidic sulfur (S) deposition, forest management, and climate change alter the health and productivity of forest trees. This study used a process model (Model of Acidification of Groundwater in Catchments [MAGIC]) to address a number of questions related to soil BC status for a group of 65 streams and their watersheds in the southern Blue Ridge physiographicprovince of the southern Appalachian Mountains. Future S deposition to the study watersheds used for the Base Scenario was specified according to proposed reductions in S emissions at the time of this study, representing a reduction of 42 % of ambient S deposition by 2020. Twenty additional simulations were considered, reflecting four alternate S deposition scenarios (6 %, 58 %, 65 %, and 78 % reduction), and various changes in timber harvest, temperature, and precipitation. Base Scenario soil exchangeable Ca and % base saturation showed decreasing trends from 1860 to 2100. Changes in tree harvesting had the largest effect on stream sum of base cations (SBC) and soil BC supply. Each of the scenario projections indicated that median year 2100 soil exchangeable Ca will be at least 20 % lower than pre-industrial values. The simulations suggested that substantial mass loss of soil BC has already occurred since pre-industrial times. Nearly the same magnitude of BC loss is expected to occur over the next 145 years, even under relatively large additional future reductions in S deposition.

Milanovich, Joseph R., and John C. Maerz. Realistic Fasting Does Not Affect Stable Isotope Levels of a Metabolically Efficient Salamander. Journal of Herpetology 47.4 (2013): 544-548.

Abstract
Stable isotopes are commonly used to examine various aspects of animal ecology. The use of stable isotopes generally proceeds under the implicit assumption that resource use is the only factor driving variation in stable isotope levels; however, a wealth of studies demonstrate that a range of common ecological factors can affect the behavior of stable isotopes in animal tissues and potentially confound inferences. For example, studies of some invertebrates and endothermic vertebrates show that animals fasted for ecologically realistic time periods have higher nitrogen (d15N) or lower carbon (d13C). We examined whether realistic fasting would influence the stable isotope composition of one of the most metabolically efficient ectothermic vertebrates, the Eastern Red-backed Salamander, Plethodon cinereus. We fasted salamanders for 7, 14, 21, 28, or 35-day intervals and examined whether d15N or d13C levels of tissues changed between fasted and fed animals. We investigated whether body condition (body mass to length and C:N [an index of lipid levels]) declined in fasted animals and whether there was a relationship between C:N and d15N or d13C. Body mass to length index and C:N, d13C, and d15N of tail and liver tissues did not differ between fasted and fed animals between 7 and 35 days. Because of their extreme metabolic efficiency, vertebrate ectotherms such as lungless salamanders (Plethodontidae) may not show the effects of fasting on stable isotopes observed in endothermic vertebrates and some invertebrates. This difference should lead to simpler interpretation of stable isotope results from field studies of these animals

Northington, R.M., Webster, J.R., Benfield, E.F., Cheever, B.M. and Niederlehner, B. 2013. Ecosystem function in Appalachian headwater streams during an active invasion by the hemlock woolly adelgid. PLoS ONE. 8(4):e61171. (DOI: 10.1371/journal.pone.0061171)

Abstract
Forested ecosystems in the southeastern United States are currently undergoing an invasion by the hemlock woolly adelgid (HWA). Previous studies in this area have shown changes to forest structure, decreases in canopy cover, increases in organic matter, and changes to nutrient cycling on the forest floor and soil. Here, we were interested in how the effects of canopy loss and nutrient leakage from terrestrial areas would translate into functional changes in streams draining affected watersheds. We addressed these questions in HWA-infested watersheds at the Coweeta Hydrologic Laboratory in North Carolina. Specifically, we measured stream metabolism (gross primary production and ecosystem respiration) and nitrogen uptake from 2008 to 2011 in five streams across the Coweeta basin. Over the course of our study, we found no change to in- stream nutrient concentrations. While canopy cover decreased annually in these watersheds, this change in light penetration did not translate to higher rates of in-stream primary production during the summer months of our study. We found a trend towards greater heterotrophy within our watersheds, where in-stream respiration accounted for a much larger component of net ecosystem production than GPP. Additionally, increases in rhododendron cover may counteract changes in light and nutrient availability that occurred with hemlock loss. The variability in our metabolic and uptake parameters suggests an actively-infested ecosystem in transition between steady states.

Novick, K., Walker, J., Chan, W., Schmidt, A., Sobek, C. and Vose, J.M. 2013. Eddy covariance measurements with a new fast-response, enclosed-path analyzer: Spectral characteristics and cross-system comparisons. Agricultural and Forest Meterology. 181:17-32. (DOI: http://dx.doi.org/10.1016/j.agrformet.2013.06.020)

Abstract
A new class of enclosed path gas analyzers suitable for eddy covariance applications combines the advantages of traditional closed-path systems (small density corrections, good performance in poor weather) and open-path systems (good spectral response, low power requirements), and permits estimates of instantaneous gas mixing ratio. Here, the extent to which these advantages are realized in field deployment is assessed, with a focus on the suitability of such an analyzer (the EC155, manufactured by Campbell Scientific) for long-term flux measurements in a new flux monitoring site in the southern Appalachians (NC, USA). The scalar-vertical velocity co-spectra for CO2 fluxes measured with the EC155 were similar to those measured with a co-located open-path system. When humidity was high, attenuation of the EC155 water vapor fluxes for non-dimensional frequencies greater than ∼2 was noted, though results from an ogive analysis suggest that eddies operating on these time scales contributed <2% of the total turbulent flux in this tall forest ecosystem. Inertial sub-range decay of the vertical velocity-scalar co-spectra generally conformed to a -7/3 power law during near-neutral atmospheric stability conditions, supporting the use of an analytical spectral correction approach to the raw measured fluxes. The EC155 fluxes computed directly from instantaneous mixing ratio agreed with will those calculated from mass–density concentration measurements, provided density terms for temperature, water vapor, and pressure were applied. Biases were observed when the EC155 flux records were compared to those measured with the open-path system. These differences were related to wind angle of attack and to an estimate of apparent fluxes related to instrument self-heating, and the biases were minimized after the application of a friction velocity filter. Finally, the EC155 considerably outperformed open-path analyzers during adverse weather conditions favorable to fog development, which occur frequently in the study site.

Ogden, L. N. Heynen, P. West, U. Oslender, P. Robbins. 2013. Global Assemblages, Resilience, and Earth Stewardship in the Anthropocene. Frontiers in Ecology and the Environment. 11: 341-347.

Abstract
In this paper, we argue that the Anthropocene is an epoch characterized not only by the anthropogenic dom- inance of the Earth’s ecosystems but also by new forms of environmental governance and institutions. Echoing the literature in political ecology, we call these new forms of environmental governance “global assemblages”. Socioecological changes associated with global assemblages disproportionately impact poorer nations and communities along the development continuum, or the “Global South”, and others who depend on natural resources for subsistence. Although global assemblages are powerful mechanisms of socioecological change, we show how transnational networks of grassroots organizations are able to resist their negative social and environmental impacts, and thus foster socioecological resilience.

Rogers, James C.; Leigh, David S. 2013. Modeling stream-bank erosion in the Southern Blue Ridge Mountains. Physical Geography. 34: 4-5. 354-372.

Abstract
Deforestation, followed by soil erosion and subsequent deposition of alluvium in valleys, played a critical role in the formation of historical terraces in much of the Southern Blue Ridge Mountains. Such terraces add a significant amount of sediment to the tributaries of the region as streams laterally erode the terrace banks. This study examined the contribution of total sediment yield derived solely from eroded stream banks in small watersheds (<20 km²), using floodplain widths as proxies for long-term lateral erosion rates. The raw data were derived from watersheds with different land covers (Coweeta Creek and Skeenah Creek watersheds in the Upper Little Tennessee River basin). Bank-derived sediment yield estimates were modeled in a Geographic Information System, using linear regression to relate floodplain widths and erodible terrace bank heights. We found total stream length to be a good predictor of both lateral erosion rates and erodible bank heights. Land cover, basin/network morphometrics, and reach-scale stream conditions were not good predictors. Modeled lateral migration and sediment yield results compare favorably to empirical measurements from five independent watersheds in the region. Modeled estimates fall within ±50% or better of the observed values, at 16.33 to 25.02 t km-2 yr-1.

Shepherd, J. Marshall, L. Bounoua and C. Mitra. 2013. Urban Climate Archipelagos: A New Framework for Urban Impacts on Climate. Earthzine.

Abstract
Earth is increasingly an “urbanized” planet. The “World Population Clock” registered a Population of 7,175,309,538 at 8:30 pm (LST) on Oct. 6, 2013. Current and future trends suggest that this population will increasingly reside in cities. Currently, 52 percent of the world population is urban, which means we are a majority “urbanized” society. Figure 1 indicates this trend will continue, with particular growth in less developed regions. In terms of ecological impacts, urbanization is one of the more significant and long-lasting forms of land transformation, and its extent of increase is at least proportional to population growth and economic development. Urbanization exerts environmental and climatic pressures on surrounding lands that are not fully understood. Viewed from the perspective of the amount of space it currently occupies, urbanization appears to be a minor form of land transformation. It is estimated that urbanization in the U.S. occupies about 3 percent of the land surface (Imhoff et al. 2004). In terms of climate impacts, urbanization affects its environment through different physical mechanisms: 1) the reduction of the fraction of vegetation and the subsequent reduction in photosynthesis and plant’s water transpiration and interception, 2) the alteration of water infiltration and surface runoff and their impacts on soil moisture and the water table, 3) the alteration of surface albedo and its effect on the surface energy partitioning, and 4) the modification of the surface roughness and its implication for the turbulent exchanges of water, energy, and momentum fluxes, all of which affect climate. The urban heat island (UHI) is a fairly well-understood urban-climate interaction (Grimmond et al. 2010; Stone et al. 2010; Zhou and Shepherd 2010). Urban areas are known to create the so-called UHI effect. On the other hand, using satellite observations over 38 of the most populous cities in the continental U.S., Imhoff et al. (2010) have shown that on a yearly average, urban areas are substantially warmer than the non-urban fringe by 2.9 degrees Celsius (C), except for urban areas within arid climates which behave as an urban heat sink. They also show that the UHI amplitude is remarkably asymmetric with an average 4.3 degrees C in summer and only 1.3 degrees C in winter. Seto and Shepherd (2009), Mitra et al. (2011) and Shepherd (2013) described how the urban environment affects other major climate systems (e.g., the water cycle, biogeochemical cycles, and weather).

Shepherd, J.M. and Andersen, T. 2013. Floods in a changing climate. Geography Compass. 7:95-115. (DOI: 10.1111/gec3.12025)

Abstract
Atmospheric warming and associated hydrological changes have implications for regional flood intensity and frequency. Climate models and hydrological models have the ability to integrate various contributing factors and assess potential changes to hydrology at global to local scales through the century. This survey of floods in a changing climate reviews flood projections based on sources of precipitation, ice and snow melt, and coastal inundation. Topographic and anthro- pogenic influences that exacerbate or reduce flood risks by altering surface runoff, infiltration, storage, and precipitation development are also considered. Flood mitigation and adaptation strategies for infrastructure, agriculture, public health, and local communities are explored along with uncertainties and challenges in flood research. Recent and upcoming datasets to help with future flood monitoring and prediction include satellite missions, advanced radar, and in-situ networks.

Stodola, K.W., Linder, E.T. & Cooper, R.J. (2013) Indirect effects of an invasive exotic species on a long-distance migratory songbird, Biol Invasions, 15: 1947. https://doi.org/10.1007/s10530-013-0423-1

Abstract
The loss of foundational tree species to non-native pests can have far reaching consequences for forest composition and function, yet little is known about the impacts on other ecosystem components such as wildlife. We had the opportunity to observe how the loss of eastern hemlock (Tsuga canadensis), due to the invasive hemlock woolly adelgid (Adelges tsugae), influenced the population ecology of the Black-throated Blue Warbler (Setophaga caerulescens) over a 7 year period. We followed the process of adelgid infestation and subsequent hemlock loss, which allowed us to investigate the patterns and mechanisms of population change. We document a precipitous decline in breeding pairs at one site where hemlock was most abundant in the understory, but not at our other two sites. We observed no changes in reproductive output or apparent survival, yet territory size increased dramatically at the most affected site, suggesting that the decline was due to a lack of colonization by new breeders. Our results demonstrate how an invasive insect pest can indirectly influence wildlife species not believed to be vulnerable and in ways not typically investigated.

Warren, R.J. II, Bahn, V. and Bradford, M. 2013. Decoupling litter barrier and soil moisture influences on the establishment of an invasive grass. Plant and Soil. (DOI: 10.1007/s11104-012-1477-z)

Warren, R.J. II, Keiser, A., Ursell, T. and Bradford, M. 2013. Habitat, dispersal and propagule pressure control exotic plant infilling within an invaded range. Ecosphere. (DOI: 10.1890/ES12-00393.1)

Warren, Robert J. and Lacy Chick. 2013. Upward ant distribution shift corresponds with minimum, not maximum, temperature tolerance. Global Change Biology 19(7):2082-2088.

Abstract
Rapid climate change may prompt species distribution shifts upward and poleward, but species movement in itself is not sufficient to establish climate causation. Other dynamics, such as disturbance history, may prompt species distribution shifts resembling those expected from rapid climate change. Links between species distributions, regional climate trends and physiological mechanism are needed to convincingly establish climate-induced species shifts. We examine a 38-year shift (1974–2012) in an elevation ecotone between two closely related ant species, Aphaenogaster picea and A. rudis. Even though A. picea and A. rudis are closely related with North American distributions that sometimes overlap, they also exhibit local- and regional-scale differences in temperature requirements so that A. rudis is more southerly and inhabits lower elevations whereas A. picea is more northerly and inhabits high elevations. We find considerable movement by the warm-habitat species upward in elevation between 1974 and 2012 with A. rudis, replacing the cold-habitat species, A. picea, along the southern edge of the Appalachian Mountain chain in north Georgia, USA. Concomitant with the distribution shifts, regional mean and maximum temperatures remain steady (1974–2012), but minimum temperatures increase. We collect individuals from the study sites and subject them to thermal tolerance testing in a controlled setting and find that maximum and minimum temperature acclimatization occurs along the elevation gradient in both species, but A. rudis consistently becomes physiologically incapacitated at minimum and maximum temperatures 2 °C higher than A. picea. These results indicate that rising minimum temperatures allow A. rudis to move upward in elevation and displace A. picea. Given that Aphaenogaster ants are the dominant woodland seed dispersers in eastern deciduous forests, and that their thermal tolerances drive distinct differences in temperature-cued synchrony with early blooming plants, these climate responses not only impact ant-ant interactions, but might have wide implications for ant plant interactions.

Whitby, Timothy G. and Michael D. Madritch. 2013. Native temperature regime influences soil response to simulated warming. Soil Biology and Biochemistry. 60:202-209. doi:10.1016/j.soilbio.2013.01.014.

Abstract
Anthropogenic climate change is expected to increase global temperatures and potentially increase soil carbon (C) mineralization, which could lead to a positive feedback between global warming and soil respiration. However the magnitude and spatial variability of belowground responses to warming are not yet fully understood. Some of the variability may depend on the native temperature regimes of soils. Soils from low temperature climates may release more C than will soils from high temperature climates because soils in cold climates are often C-rich and may experience more warming. We investigated whether soils from low native temperatures respired more than did soils from high native temperatures. We collected intact soil cores from three elevational transects along a latitudinal gradient in the forests of southern Appalachian Mountains. Soil cores were incubated for 292 days at low, medium, and high temperatures (separated by 3 C each) with diurnal temperature and light regimes that simulated realistic temperature changes likely to occur within the next century. The native temperature regimes of soils negatively influenced soil respiration, such that soils from cold climates respired more in response to experimental warming than did soils from warm climates. Conversely, soils from warm climates mineralized the largest proportion of available soil C and available soil nitrogen in response to warming. Across all soils, modest experimental warming increased soil respiration, the proportion of available soil C that was being respired (respiration/soil C), and the proportion of soil nitrogen that was mineralized (N min/soil N). Taken together, these data suggest that soils from low native temperatures have a greater potential to release C in response to climate warming because the C stocks are larger and respiration rates will be higher than those in soils from high native temperatures.

Wolner, C.W., Moore, L.J., Young, D.R., Brantley, S.T., Bissett, S.N. and McBride, R.A. 2013. Ecomorphodynamic feedbacks and barrier island response to disturbance: Insights from the Virginia Barrier Islands, Mid-Atlantic Bight, USA. Geomorphology. 199:115-128.

Abstract
Ecomorphodynamic feedbacks play an important role in the susceptibility and response of barrier islands to disturbance by overwash. Dune-building grasses, like Ammophila breviligulata, can help to restore areas of high relief after overwash events (i.e., resist disturbance). If overwash recurs before dunes have reestablished, however, overwash-adapted “maintainer” species, like Spartina patens (upright variety), may preferentially survive. Maintainer species help to preserve low, flat topography, thereby increasing the likelihood of future overwash (i.e., reinforcing disturbance). Under frequent disturbance conditions, this positive feedback may lead to overwash persistence. We explore the potential influence of the maintainer feedback on two morphologically distinct barrier islands in the Virginia Coast Reserve (VCR), located in the Mid-Atlantic Bight of the U.S. East Coast. Combined topographic and vegetation surveys show that on Hog Island (high-relief, rotating), where dunes dominated by A. breviligulata are ubiquitous, overwash zones are currently limited in extent and related to beach width rather than dominance by S. patens. Historical aerial photos and stratigraphic evidence (ground-penetrating radar, cores) indicate that gradual recovery has taken place following overwash events on Hog Island, except where the beach is narrow and eroding. Conversely, on Metompkin Island (low-relief, transgressing), overwash is widespread and dominated by S. patens, particularly along the rapidly migrating northern half of the island, where shell armoring is also common. Overwash has generally been more prevalent and persistent here than on Hog Island. We present a new conceptual model of the response of barrier islands to disturbance incorporating ecological and physical processes. Our findings suggest that in barrier systems where both dune-building grasses and overwash-adapted maintainer species are common (like the VCR), the maintainer feedback is likely to be a more important dynamic on islands already susceptible to frequent disturbance because of physical factors. The maintainer feedback, therefore, has the potential to accelerate large-scale shifts from dune-dominated to overwash-dominated barrier morphologies as the effects of climate change (increased storm intensity, sea level rise) cause overwash to become more frequent.

Bain, D. J, Green, M. B, Campbell, J. L, Chamblee, J.F., Chaoka, S., Fraterrigo, J.M., Kaushal, S. S, Martin, S. L, Jordan, T. E, Parolari, A. J, Sobczak, W. V, Weller, D. E, Wolheim, W. W, Boose, E. R, Duncan, J., Gettel, G. M, Hall, B. R, Kumar, P., Thompson, J. R, Vose, J.M., Elliott, E. M and Leigh, D.S. 2012. Legacy Effects in Material Flux: Structural Catchment Changes Predate Long-Term Studies. Bioscience. 62(6):575-584.

Abstract
Legacy effects of past land use and disturbance are increasingly recognized, yet consistent definitions of and criteria for defining them do not exist. To address this gap in biological- and ecosystem-assessment frameworks, we propose a general metric for evaluating potential legacy effects, which are computed by normalizing altered system function persistence with duration of disturbance. We also propose two distinct legacy-effect categories: signal effects from lags in transport and structural effects from physical landscape changes. Using flux records for water, sediment, nitrogen, and carbon from long-term study sites in the eastern United States from 1500 to 2000, we identify gaps in our understanding of legacy effects and reveal that changes in basin sediment dynamics precede instrumented records. These sediment dynamics are not generally incorporated into interpretations of contemporary records, although their potential legacy effects are substantial. The identification of legacy effects may prove to be a fundamental component of landscape management and effective conservation and restoration practice.

Band, L.E., Hwang, T., Hales, T., Vose, J.M. and Miniat, C.F. 2012. Ecosystem processes at the watershed scale: Mapping and modeling ecohydrological controls of landslides. Geomorphology. 137(1):159-167.

Abstract
Mountain watersheds are sources of a set of valuable ecosystem services as well as potential hazards. The former include high quality freshwater, carbon sequestration, nutrient retention, and biodiversity, whereas the latter include flash floods, landslides and forest fires. Each of these ecosystem services and hazards represents different elements of the integrated and co-evolved ecological, hydrological and geomorphic subsystems of the watershed and should be approached analytically as a coupled land system. Forest structure and species are important influences on the partitioning of precipitation, the lateral redistribution of water, runoff and sediment production, weathering and soil development. Forest regulation of hydrologic dynamics contributes to the development of patterns of soil pore pressure and slope instability during storms or snowmelt. The spatial patterns of root depth, structure and strength, developed by the below ground allocation of carbon in the forest canopy in response to limiting resources of water and nutrients, contributes to slope stability and drainage, and the maintenance of stomatal conductance linking water and carbon cycling. This in turn provides the photosynthate required to build leaf area, stem and root biomass. The linked ecological, hydrologic and geomorphic systems are characterized by specific catenary patterns that should be captured in any coupled modeling approach. In this paper we extend an ecohydrological modeling approach to include hydrologic and canopy structural pattern impacts on slope stability, with explicit feedbacks between ecosystem water, carbon and nutrient cycling, and the transient development of landslide potential in steep forested catchments. Using measured distributions of canopy leaf area index, and empirically modeled soil depth and root cohesion, the integrated model is able to generate localized areas of past instability without specific calibration or training with mapped landslides. As the model has previously been shown to simulate space/time patterns of coupled water, carbon and nutrient cycling, the integration of slope stability as a function of hydrologic, ecosystem and geomorphic processes provides the ability to closely link multiple ecosystem services with a unified approach.

Belden, Lisa K., William E. Peterman, Stephen A. Smith, Lauren R. Brooks, E.F. Benfield, Wesley P. Black, Zhaomin Yang and Jeremy M. Wojdak. 2012. Metagonimoides oregonensis (Heterophyidae: Digenea) Infection In Pleurocerid Snails and Desmognathus quadramaculatus Salamander Larvae In Southern Appalachian Streams. Journal of Parasitology 98(4):760-767.

Abstract
Metagonimoides oregonensis (Heterophyidae) is a little-known digenetic trematode that uses raccoons and possibly mink as definitive hosts, and stream snails and amphibians as intermediate hosts. Some variation in the life cycle and adult morphology in western and eastern populations has been previously noted. In the southern Appalachians, Pleurocera snails and stream salamanders, e.g., Desmognathus spp., are used as intermediate hosts in the life cycle. We completed a series of studies in this system examining some aspects of larval trematode morphology and first and second intermediate host use. Molecular sequencing of the 28S rDNA of cercariae in our survey placed them clearly within the heterophyid family. However, light and scanning electron microscopy revealed both lateral and dorso-ventral finfolds on the cercariae in our region, whereas original descriptions of M. oregonensis cercariae from the west coast indicate only a dorso-ventral finfold, so further work on the systematics of this group may be warranted. A survey of first intermediate host, Pleurocera proxima, from 7 streams in the region identified only M. oregonensis, virgulate-type cercariae, and cotylomicrocercous-type cercariae in the streams, with M. oregonensis having the highest prevalence, and the only type present that use amphibians as second intermediate hosts. Based on clearing and staining of 6 Desmognathus quadramaculatus salamander larvae, we found that individual salamanders could have over 600 metacercariae, which form between muscle fibers throughout the body. Histological observations suggest that the metacercariae do not cause excessive tissue damage or inflammation, and likely persist through metamorphosis, thereby transmitting potentially large numbers of worms to definitive host raccoons foraging along streams.

Benstead, Jonathan P., and David S. Leigh, 2012, An Expanded Role for River Networks. Nature Geoscience 5:678-679.

Abstract
Estimates of stream and river area have relied on observations at coarse resolution. Consideration of the smallest and most dynamic streams could reveal a greater role for river networks in global biogeochemical cycling than previously thought.

Block, C., Knoepp, J.D., Elliott, K. and Fraterrigo, J.M. 2012. Impacts of Hemlock Loss on Nitrogen Retention Vary with Soil Nitrogen Availability in the Southern Appalachian Mountains. Ecosystems. 15(7):1108-1120. (DOI: 10.1007/s10021-012-9572-9)

Abstract
The impacts of exotic insects and pathogens on forest ecosystems are increasingly recognized, yet the factors influencing the magnitude of effects remain poorly understood. Eastern hemlock (Tsuga canadensis) exerts strong control on nitrogen (N) dynamics, and its loss due to infestation by the hemlock woolly adelgid (Adelges tsugae) is expected to decrease N retention in impacted stands. We evaluated the potential for site variation in N availability to influence the magnitude of effects of hemlock decline on N dynamics in mixed hardwood stands. We measured N pools and fluxes at three elevations (low,mid, high) subjected to increasing atmospheric N deposition where hemlock was declining or absent (as reference), inwestern North Carolina. Nitrogen pools and fluxes varied substantially with elevation and increasing N availability. Total forest floor and mineral soil N increased (P < 0.0001, P = 0.0017, resp.) and forest floor and soil carbon (C) to N ratio decreased with elevation (P < 0.0001, P = 0.0123, resp.), suggesting that these high elevation pools are accumulating available N. Contrary to expectations, subsurface leaching of inorganic N was minimal overall (<1 kg ha-1 9 months-1), and was not higher in stands with hemlock mortality. Mean subsurface flux was 0.16 ± 0.04 (SE) (kg N ha-1 100 days-1) in reference and 0.17 ± 0.05 (kg N ha-1 100 days-1) in declining hemlock stands. Moreover, although subsurface N flux increased with N availability in reference stands, there was no relationship between N availability and flux in stands experiencing hemlock decline. Higher foliar N and observed increases in the growth of hardwood species in high elevation stands suggest that hemlock decline has stimulated N uptake and growth by healthy vegetation within this mixed forest, and may contribute to decoupling the relationship between N deposition and ecosystem N flux.

Bradford, M.A., Strickland, M.S., Devore, J.L., Maerz, J.C. (2012) Root carbon flow from an invasive plant to belowground foodwebs. Plant and Soil. DOI: 10.1007/s11104-012-1210-y

Abstract
Aims Soil foodwebs are based on plant production. This production enters belowground foodwebs via numerous pathways, with root pathways likely dominating supply. Indeed, root exudation may fuel 30–50 % of belowground activity with photosynthate fixed only hours earlier. Yet we have limited knowledge of root fluxes of recent-photosynthate from invasive plants to belowground foodwebs. Methods Using stable isotopes, we quantify the proportion of recent-photosynthate transferred belowground from the invasive grass Microstegium vimineum A. Camus, a widespread invader of forest understory. Given its minimal root biomass (~8 % of individual mass), we expected exudation to contribute little to belowground foodwebs. Results Within 2 days of 13C-labeling, we recover ~15 % of photosynthate carbon in microbial biomass. Recovery in root and dissolved organic carbon pools is consistently low (<2 %), suggesting these pools operate as ‘pipelines’ for carbon transport to soil microbes. The recovery of the label in wolf spiders –forest floor predators that feed on soil animals – highlights that root inputs of recent photosynthate can propagate rapidly through belowground foodwebs. Conclusions Our results suggest that root carbonexudation,an unexplored process of invasive grass inputs to forest foodwebs, may be an important pathway through which invasive species affect the structure and function of recipient ecosystems.

Cheever, B.M., E.B. Kratzer, and J.R. Webster. 2012. Immobilization and mineralization of N and P by heterotrophic biofilms during leaf decomposition. Freshwater Science 31:133-147.

Abstract
According to theory, the rate and stoichiometry of microbial mineralization depend, in part, on nutrient availability. For microbes associated with leaves in streams, nutrients are available from both the water column and the leaf. Therefore, microbial nutrient cycling may change with nutrient availability and during leaf decomposition. We explored spatial and temporal patterns of mineralization by heterotrophic microbes by placing packs of red maple leaves at sites in 5 Appalachian streams spanning a range of N and P availability. We collected packs 4 times from each site. Leaf disks from these packs were incubated in microcosms, and uptake rates and steady-state concentrations of NH + and soluble reactive P (SRP) were used to calculate mineralization rates. N uptake peaked between 50 and 60 d, whereas P uptake peaked ,10 d later. Clear patterns were found for fungal biomass-specific uptake or mineralization fluxes of either nutrient over time or space, but the microbes grown in the site with the lowest nutrient availability had the highest fungal biomass-specific cycling. The ability of microbes to access nutrients from their substrate may prevent dissolved nutrient availability from being a strong driver of microbial nutrient cycling.

Clark, J.S. 2012. The coherence problem with the Unified Neutral Theory of Biodiversity. Trends in Ecology and Evolution, 27:198-202.

Abstract
The Unified Neutral Theory of Biodiversity (UNTB), proposed as an alternative to niche theory, has been viewed as a theory that species coexist without niche differences, without fitness differences, or with equal probability of success. Support is claimed when models lacking species differences predict highly aggregated metrics, such as species abundance distributions (SADs) or species area distributions (SARs). Here, I summarize why UNTB generates confusion, and is not actually relevant to niche theory (i.e. an explanation for why and how many species coexist). Equal probability is not a theory, but lack of one; it does not include or exclude any process relevant to coexistence of competitors. Models lacking explicit species can make useful predictions, but this does not support neutral theory. I provide s suggestions that could help reduce confusion generated by the debate.

Clark, J.S., B.D. Soltoff, A.S. Powell, and Q.D. Read. 2012. Evidence from individual inference for high-dimensional coexistence: long term experiments on recruitment response. PLoS One, 7 e30050. doi:10.1371/journal.pone.0030050.

Abstract
Background For competing species to coexist, individuals must compete more with others of the same species than with those of other species. Ecologists search for tradeoffs in how species might partition the environment. The negative correlations among competing species that would be indicative of tradeoffs are rarely observed. A recent analysis showed that evidence for partitioning the environment is available when responses are disaggregated to the individual scale, in terms of the covariance structure of responses to environmental variation. That study did not relate that variation to the variables to which individuals were responding. To understand how this pattern of variation is related to niche variables, we analyzed responses to canopy gaps, long viewed as a key variable responsible for species coexistence. Methodology/Principal Findings A longitudinal intervention analysis of individual responses to experimental canopy gaps with 12 yr of pre-treatment and 8 yr post-treatment responses showed that species-level responses are positively correlated – species that grow fast on average in the understory also grow fast on average in response to gap formation. In other words, there is no tradeoff. However, the joint distribution of individual responses to understory and gap showed a negative correlation – species having individuals that respond most to gaps when previously growing slowly also have individuals that respond least to gaps when previously growing rapidly (e.g., Morus rubra), and vice versa (e.g., Quercus prinus). Conclusions/Significance Because competition occurs at the individual scale, not the species scale, aggregated species-level parameters and correlations hide the species-level differences needed for coexistence. By disaggregating models to the scale at which the interaction occurs we show that individual variation provides insight for species differences.

Clark, J.S., D. M. Bell, M. Kwit, A. Powell, R. Roper, A. Stine, B. Vierra, and K. Zhu. 2012. Individual-scale inference to anticipate climate-change vulnerability of biodiversity. Philosophical Transactions of the Royal Society B, 367, 236-246.

Abstract
Anticipating how biodiversity will respond to climate change is challenged by the fact that climate variables affect individuals in competition with others, but interest lies at the scale of species and landscapes. By omitting the individual scale, models cannot accommodate the processes that determine future biodiversity. We demonstrate how individual-scale inference can be applied to the problem of anticipating vulnerability of species to climate. The approach places climate vulnerability in the context of competition for light and soil moisture. Sensitivities to climate and competition interactions aggregated from the individual tree scale provide estimates of which species are vulnerable to which variables in different habitats. Vulnerability is explored in terms of specific demographic responses (growth, fecundity and survival) and in terms of the synthetic response (the combination of demographic rates), termed climate tracking. These indices quantify risks for individuals in the context of their competitive environments. However, by aggregating in specific ways (over individuals, years, and other input variables), we provide ways to summarize and rank species in terms of their risks from climate change.

Clark, James S., David M. Bell, Matthew Kwit, A., Anne Stine, Ben Vierra, and Kai Zhu. 2012. Individual scale inference to anticipate climate change vulnerability of biodiversity. Philosophical Transactions of the Royal Society B 367:236-246.

Abstract
Anticipating how biodiversity will respond to climate change is challenged by the fact that climate variables affect individuals in competition with others, but interest lies at the scale of species and landscapes. By omitting the individual scale, models cannot accommodate the processes that determine future biodiversity. We demonstrate how individual-scale inference can be applied to the problem of anticipating vulnerability of species to climate. The approach places climate vulnerability in the context of competition for light and soil moisture. Sensitivities to climate and competition interactions aggregated from the individual tree scale provide estimates of which species are vulnerable to which variables in different habitats. Vulnerability is explored in terms of specific demographic responses (growth, fecundity and survival) and in terms of the synthetic response (the combination of demographic rates), termed climate tracking. These indices quantify risks for individuals in the context of their competitive environments. However, by aggregating in specific ways (over individuals, years, and other input variables), we provide ways to summarize and rank species in terms of their risks from climate change.

Cumming, G., Norwood, C., 2012. The Community Voice Method: Using participatory research and filmmaking to foster dialog about changing landscapes. Landscape and Urban Planning, Vol. 105:4, April 2012, p. 434-444

Abstract
The Community Voice Method is a stakeholder engagement approach designed to foster more inclusive, informed, and ongoing civic dialog in communities without a history of successful planning initiatives. The method begins with an iterative participatory research process, resulting in the creation of an original documentary film compiled from ethnographic interviews with a wide range of stakeholders. The film, which presents a research-based distillation of local civic discourse around the topic of interest, is used in combination with quantitative data presentations to stimulate deliberation during subsequent deliberative public meetings. Using findings from a Community Voice project in Macon County, North Carolina (USA), we argue that, by preceding public meetings with participatory research, the Community Voice Method was able to promote inclusive civic dialog; provide meeting participants with accessible, trustworthy information; and help build ongoing community capacity to address local land use issues.

Eggert, S.L., Wallace, J.B., Meyer, J.L. and Webster, J. 2012. Storage and export of organic matter in a headwater stream: responses to long-term detrital manipulations. Ecosphere. 3:75. (DOI: doi.org/10.1890/ES12-00061.1)

Abstract
Riparian habitats provide organic matter inputs that influence stream biota and ecosystem processes in forested watersheds. Over a 13-yr period, we examined the effects of litter exclusion, small- and large-wood removal, and the addition of leaf species of varying detrital quality on organic matter standing crop and export of organic and inorganic particles in a high-gradient headwater stream. Using eight pretreatment years of export data and two pretreatment years of particulate organic matter (POM) standing crop data, we report on 21 and 15 years of continuous export and POM standing crop results, respectively. Litter exclusion resulted in the elimination of leaf standing crop by the end of year three. Wood and fine benthic organic matter (FBOM) standing crops declined significantly during the exclusion and wood removal periods, but never completely disappeared. Following the introduction of artificial wood structures for retention, the addition of fast, slow, and mixed breakdown leaves in the treatment stream resulted in significantly increased mean annual leaf standing crops. After five years of leaf addition, FBOM standing crop and fine particulate organic matter (FPOM) export remained below pre-treatment levels. The reduction in leaf standing crop in the treatment stream resulted in significant increases in FPOM (2×), fine inorganic particulate (3×), and gravel export (10×). After small wood removal we observed significant increases in export of fine inorganic particulates (2×) and gravel (7×) from the treatment stream. A greater proportion of coarse and FBOM standing crop was exported from the treatment stream during the litter exclusion and small wood removal periods than from the reference stream. Following the addition of slow and mixed leaves this trend was reversed, demonstrating the importance of leaf standing crop in the retention of POM. Our long-term experiment demonstrates that the quantity and type of riparian inputs to forested headwater streams will affect POM standing crop and export of POM and sediments to downstream ecosystems, and that small wood is more critical to retaining sediments and POM in small streams than previously recognized.

Elliott, K.J., J.M. Vose, J.D. Knoepp, B.D. Clinton. 2012. Restoring shortleaf pine (Pinus echinata)-hardwood ecosystems severely impacted by the southern pine beetle (Dendroctonus frontalis Zimmerman). Forest Ecology and Management 274:181-200.

Abstract
In the Southern Appalachian Mountains of eastern USA, pine-hardwoodecosystems have been severelyimpacted by the interactions of past land use, fire exclusion, drought, and southernpinebeetle (SPB, Dendroctonusfrontalis). We examined the effects of restoration treatments: burn only (BURN); cut + burn on dry sites (DC + B); cut + burn on sub-mesic sites (MC + B); and reference sites (REF; no cutting or burning) on shortleafpine-hardwood forests. We also evaluated the effectiveness of seeding native bluestem grasses. Structural (down wood, live and dead standing trees, shrubs, herbaceous layer) and functional (forest floor mass, C, and N; soil C, N, P, and cations; and soil solution N and P) attributes were measured before and the first and second growing seasons after treatment. We used path analysis to test our conceptual model that restoration treatments will have direct and indirect effects on these ecosystems. Total aboveground mass loss ranged from 24.33 Mg ha-1 on the BURN to 74.44 Mg ha-1 on the DC + B treatment; whereas, REF gained 13.68 Mg ha-1 between pre-burn and post-burn. Only DC + B sites had increased soil NO3–N, NH4–N Ca, Mg, and PO4–P and soil solution NO3–N, NH4–N, O–PO4 for several months. We found a significant increase in the density of oak species (Quercus alba, Q. coccinea, Q. montana, Q. rubra, and Q. velutina) on all burn treatments. However, oaks accounted for a smaller proportion of the total stem density than red maple, other tree species, and shrubs. The high densities of woody species other than oaks, coupled with the fast growth rates of some of these species, suggests that oaks will continue to be at a competitive disadvantage in these pine-hardwood communities through time, without further intervention. Pine regeneration was not improved on any of our burned sites with little to no recruitment of pines into the understory after two years and the pine saplings that were present before the burns were killed by fire on all sites. We found an increase in herbaceous layer cover and richness on all fire treatments. DC + B had higher bluestem grass cover than the other treatments, and it was the only treatment with increased bluestem grass cover between the first (2.96%, SE = 0.29) and second (6.88%, SE = 0.70) growing seasons. Our path model showed that fire severity explained a large proportion of the variation in overstory response; and fire severity and overstory response partially explained soil NO3–N. These variables, directly and indirectly, explained 64% of the variation in soil solution NO3–N at 30 cm soil depth (within the rooting zone for most plants). We found a good-fit path model for herbaceous layer response in the second growing season, where fire severity had direct effects on overstory and herbaceous layer responses and indirect effects on herbaceous layer response mediated through overstory response. Our path model explained 46% and 42% of the variation in herbaceous layer cover and species richness, respectively.

Elliott, K.J., J.M. Vose. 2012. Age and distribution of an evergreen clonal shrub in the Coweeta Basin: Rhododendron maximum L. Journal of Torrey Botanical Society 139(2):149-166.

Abstract
Rhododendron maximum L. is an evergreen, clonal shrub that forms a dominant sub-canopy layer and is a key species in southern Appalachian forests. We investigated the age and distribution of R. maximum across the Coweeta Basin, a 1626 ha watershed in western North Carolina. We selected 16 perennial, second-order streams and used a Global Positioning System to establish site boundaries and map the coverage of R. maximum across the hillslopes from stream to ridge. In each site, three transects from stream edge to the ridge were used to measure diameters of overstory trees (= 2.5 cm dbh), tree saplings (< 2.5 cm dbh) and shrubs including R. maximum stems. Along each transect, we cut cross-sections of R. maximum ramets and extracted increment cores from nearest neighbor trees to determine ages. The 16 sites ranged in size from 0.3 to 1.9 ha depending on the distance from stream to ridge. Rhododendron maximum cover ranged from 25 to 100% and ages ranged from 6 to 120 years. Rhododendron maximum establishment year showed a skewed unimodal distribution with the peak establishment occurring between 1928 and 1940. Although the R. maximum age and distance-from-stream relationship was statistically significant, the relationship was not meaningful as distance-from-stream only explained 2.6% of the variation in R. maximum age (r2 = 0.026, P = 0.0003, n = 487). Distance from stream only explained 4.2% of the variation in overstory tree age (r2 = 0.042, P = 0.0015, n=237). It appears that R. maximum has not expanded upslope over the last 100 years; rather the ranges in sizes and ages suggest that ramets are recruiting under established R. maximum canopies particularly in the wetter, near stream locations. - See more at: http://www.srs.fs.usda.gov/pubs/41289#sthash.TXXDCA5s.dpuf

Ford, C.R., Elliott, K.J., Clinton, B.D., Kloeppel, B.D., Vose, J.M., 2012. Forest dynamics following eastern hemlock mortality in the southern Appalachians. Oikos 121:4, April 2012, p. 523-536, doi: 10.1111/j.1600-0706.2011.19622.x, Nordic Society Oikos

Abstract
Understanding changes in community composition caused by invasive species is critical for predicting effects on ecosystem function, particularly when the invasive threatens a foundation species. Here we focus on dynamics of forest structure, composition and microclimate, and how these interact in southern Appalachian riparian forests following invasion by hemlock woolly adelgid, HWA, Adelges tsugae. We measured and quantified changes in microclimate; canopy mortality; canopy and shrub growth; understory species composition; and the cover and diversity in riparian forests dominated by eastern hemlock Tsuga canadensis over a period of seven years. Treatments manipulated hemlock mortality either through invasion (HWA infested stands) or girdling (GDL) hemlock trees. Mortality was rapid, with 50% hemlock tree mortality occurring after six years of invasion, in contrast to more than 50% mortality in two years following girdling. Although 50% of hemlock trees were still alive five years after infestation, leaf area lost was similar to that of girdled trees. As such, overall responses over time (changes in light transmittance, growth, soil moisture) were identical to girdled stands with 100% mortality. Our results showed different growth responses of the canopy species, shrubs and ground layer, with the latter being substantially influenced by presence of the evergreen shrub, rhododendron Rhododendron maximum. Although ground layer richness in the infested and girdled stands increased by threefold, they did not approach levels recorded in hardwood forests without rhododendron. Increased growth of co-occurring canopy trees occurred in the first few years following hemlock decline, with similar responses in both treatments. In contrast, growth of rhododendron continued to increase over time. By the end of the study it had a 2.6-fold higher growth rate than expected, likely taking advantage of increased light available during leaf-off periods of the deciduous species. Increased growth and dominance of rhododendron may be a major determinant of future responses in southern Appalachian ecosystems; however, our results suggest hemlock will be replaced by a mix of Acer, Betula, Fagus and Quercus canopy genera where establishment is not limited by rhododendron.

Ghosh, S., A.E. Gelfand, K. Zhu, and J.S. Clark. 2012. The k-ZIG: flexible modeling for zero-inflated counts. Biometrics, on-line edition.

Abstract
Many applications involve count data from a process that yields an excess number of zeros. Zero-inflated count models, in particular, zero-inflated Poisson (ZIP) and zero-inflated negative binomial (ZINB) models, along with Poisson hurdle models, are commonly used to address this problem. However, these models struggle to explain extreme incidence of zeros (say more than 80%), especially to find important covariates. In fact, the ZIP may struggle even when the proportion is not extreme. To redress this problem we propose the class of k-ZIG models. These models allow more flexible modeling of both the zero-inflation and the nonzero counts, allowing interplay between these two components. We develop the properties of this new class of models, including reparameterization to a natural link function. The models are straightforwardly fitted within a Bayesian framework. The methodology is illustrated with simulated data examples as well as a forest seedling dataset obtained from the USDA Forest Service’s Forest Inventory and Analysis program.

Ghosh, S., Gelfand, A. and Clark, J.S. 2012. Inference for size demography from point pattern data using integral projection models. Journal of Agricultural, Biological and Environmental Statistics. (DOI: 10.1007/s13253-012-0121-y)

Abstract
Population dynamics with regard to evolution of traits has typically been studied using matrix projection models (MPMs). Recently, to work with continuous traits, in- tegral projection models (IPMs) have been proposed. Imitating the path with MPMs, IPMs are handled first with a fitting stage, then with a projection stage. Fitting these models has so far been done only with individual-level transition data. These data are used to estimate the demographic functions (survival, growth, fecundity) that comprise the kernel of the IPM specification. Then, the estimated kernel is iterated from an initial trait distribution to project steady state population behavior under this kernel. When trait distributions are observed over time, such an approach does not align projected distributions with these observed temporal benchmarks. The contribution here, focusing on size distributions, is to address this issue. Our concern is that the above approach introduces an inherent mismatch in scales. The re- distribution kernel in the IPM proposes a mechanistic description of population level redistribution. A kernel of the same functional form, fitted to data at the individual level, would provide a mechanistic model for individual-level processes. Resulting parameter estimates and the associated estimated kernel are at the wrong scale and do not allow population-level interpretation. Our approach views the observed size distribution at a given time as a point pattern over a bounded interval. We build a three-stage hierarchical model to infer about the dynamic intensities used to explain the observed point patterns. This model is driven by a latent deterministic IPM and we introduce uncertainty by having the operating IPM vary around this deterministic specification. Further uncertainty arises in the realiza- tion of the point pattern given the operating IPM. Fitted within a Bayesian framework, such modeling enables full inference about all features of the model. Such dynamic modeling, optimized by fitting to data observed over time, is better suited to projection. Exact Bayesian model fitting is very computationally challenging; we offer approx- imate strategies to facilitate computation. We illustrate with simulated data examples as well as well as a set of annual tree growth data from Duke Forest in North Carolina. A further example shows the benefit of our approach, in terms of projection, compared with the foregoing individual level fitting.

Hales, T.C., Scharer, K.M., Wooten, R.M., 2012. Southern Appalachian hillslope erosion rates measured by soil and detrital radiocarbon in hollows. Geomorphology 138:1, February 2012, p. 121–129, Elsevier

Abstract
Understanding the dynamics of sediment generation and transport on hillslopes provides important constraints on the rate of sediment output from orogenic systems. Hillslope sediment fluxes are recorded by organic material found in the deposits infilling unchanneled convergent topographic features called hollows. This study describes the first hollow infilling rates measured in the southern Appalachian Mountains. Infilling rates (and bedrock erosion rates) were calculated from the vertical distribution of radiocarbon ages at two sites in the Coweeta drainage basin, western North Carolina. At each site we dated paired charcoal and silt soil organic matter samples from five different horizons. Paired radiocarbon samples were used to bracket the age of the soil material in order to capture the range of complex soil forming processes and deposition within the hollows. These dates constrain hillslope erosion rates of between 0.051 and 0.111 mm yr-1. These rates are up to 4 times higher than spatially-averaged rates for the Southern Appalachian Mountains making creep processes one of the most efficient erosional mechanisms in this mountain range. Our hillslope erosion rates are consistent with those of forested mountain ranges in the western United States, suggesting that the mechanisms (dominantly tree throw) driving creep erosion in both the western United States and the Southern Appalachian Mountains are equally effective.

Hersh, M.H., J.S. Clark, and R. Vilgalys. 2012. Evaluating the impacts of fungal seedling pathogens on temperate forest seedling survival. Ecology, 93: 511-520.

Abstract
Host-specific mortality driven by natural enemies is a widely discussed mechanism for explaining plant diversity. In principle, populations of plant species can be regulated by distinct host-specific natural enemies that have weak or nonexistent effects on heterospecific competitors, preventing any single species from becoming dominant and thus promoting diversity. Two of the first steps in exploring the role of natural enemies in diversity regulation are to (1) identify potential enemies and (2) evaluate their levels of host specificity by determining if interactions between any one host and its enemy have equivalent survival impacts on co-occurring host species. We developed a bioinformatics framework to evaluate impacts of potential pathogens on seedling survival, for both single and multiple infections. Importantly, we consider scenarios not only if there are specialist pathogens for each plant, but also when generalist pathogens have differential effects on multiple host species, and when co-infection has species-specific effects. We then applied this analytical framework to a field experiment using molecular techniques to detect potential fungal pathogens on co-occurring tree seedling hosts. Combinatorial complexity created by 160 plant–fungus interactions was reduced to eight combinations that affect seedling survival. Potential fungal pathogens had broad host ranges, but seedling species were each regulated by different combinations of fungi or by generalist fungi that had differential effects on multiple plant species. Soil moisture can have the potential to shift the nature of the interactions in some plant–fungal combinations from neutral to detrimental. Reassessing the assumption of single-enemy–single-host interactions broadens the mechanisms through which natural enemies can influence plant diversity.

Hoffman, Ava (2012). Estimating Tree Transpiration Accurately Depends on Wood Type and Species: A Study of Four Southern Appalachian Tree Species. The Oculus: The Virginia Journal of Undergraduate Research 11:30-34. University of Virginia.

Abstract
The measurement of sap movement in trees is a valuable way to estimate forest evapotranspiration, or the return of water vapor to the atmosphere. The accuracy of these measurements is essential to determining forest evapotranspiration. Importantly, forest evapotranspiration is a major component of water budget, and subsequent water lost through this process affects other fluxes such as streamflow and surface water supply. Using a dual thermal dissipation probe system inserted into sapwood, the difference in temperature (AT) between the two probes can be related to sap flux density using an empirically derived equation. The universality of the power function coefficients proposed by Granier in this empirical equation has recently come into question regarding different tree species. Notably, Granier's coefficients may not be universal among different wood types and among trees with varying sapwood to heartwood ratios. It has been suggested that each specie* should be validated before using the universal coefficients. Using four tree species indigenous to the southern Appalachians (Betula lenta, Liriodendron tulipifera, Nyssa sylvatica, Rhododendron maximum), this study estimates sap flux through excised woody stems using two independent methods: gravimetric and thermal dissipation. This study evaluates whether the species differ significantly among each other by comparing aforementioned gravimetric measurements. Replicates of excised stems were selected from trees growing in the Coweeta basin. Our results indicated that three of the four species require coefficients that differ from Granier's (Betula, Nyssa, Rhododendron). Furthermore, there are significant differences between all but two of the species (Liriodendron and Rhododendron). Future studies will focus on testing other major tree species in the southern Appalachians to improve the accuracy of stand-level transpiration measurements.

Hwang, T., Band, L.E., Vose, J.M. and Tague, C. 2012. Ecosystem processes at the watershed scale: Hydrologic vegetation gradient as an indicator for lateral hydrologic connectivity of headwater catchments. Water Resources Research. 48. W06514. (DOI: 10.1029/2011WR011301)

Abstract
Lateral water flow in catchments can produce important patterns in water and nutrient fluxes and stores and also influences the long-term spatial development of forest ecosystems. Specifically, patterns of vegetation type and density along hydrologic flow paths can represent a signal of the redistribution of water and nitrogen mediated by lateral hydrologic flow. This study explores the use of emergent vegetation patterns to infer ecohydrologic processes and feedbacks in forested headwater catchments. We suggest a hydrologic gradient of vegetation density as an indicator of lateral connectivity within headwater catchments. We define the hydrologic vegetation gradient (HVG) as the increase of normalized difference vegetation index per unit increase of the topographic wetness index. HVG are estimated in different headwater catchments in the Coweeta Hydrologic Laboratory using summer IKONOS imagery. We use recession slope analysis with gauge data and a distributed ecohydrological model to characterize the patterns of seasonal flow regimes within the catchments. Correlations between HVG, catchment runoff, early recession parameters, and model parameters show the interactive role of vegetation and lateral hydrologic connectivity of systems in addition to climatic and geomorphic controls. This suggests that HVG effectively represents the level of partitioning between localized water use and lateral water flow along hydrologic flow paths, especially during the growing season. It also presents the potential to use simple remotely sensed hydrologic vegetation gradients as an indicator of lateral hydrologic connectivity to extrapolate recession behavior and key model parameters of distributed hydrological models for ungauged headwater catchments.

Jackson, M.M., Turner, M.G., Pearson, S.M. and Ives, A.R. 2012. Seeing the forest and the trees: multilevel models reveal both species and community patterns. Ecosphere. 3(9). (DOI: http://dx.doi.org/10.1890/ES12-00116.1)

Abstract
Studies designed to understand species distributions and community assemblages typically use separate analytical approaches (e.g., logistic regression and ordination) to model the distribution of individual species and to relate community composition to environmental variation. Multilevel models (MLMs) offer a promising strategy for integrating species and community-level analyses. Here, we demonstrate how MLMs can be used to analyze differences in species composition of communities across environmental gradients. We first use simulated data to show that MLMs can outperform three standard methods that researchers use to identify environmental drivers of the species composition of communities, redundancy analysis (RDA), canonical correspondence analysis (CCA), and nonmetric multidimensional scaling (NMDS). In particular, MLMs can separate the effects of collinearity among environmental drivers and factor out the effect of changes in overall species abundances or occurrences that do not involve changes in composition. We then apply MLMs to presence/absence data for 14 species of understory herbs and topographic, biotic, and edaphic variables measured in 54 forested plots in the Southern Appalachian Mountains. In addition to providing information about community composition, MLMs simultaneously identify the responses of individual species to the environmental variables. Thus, MLMs not only have potentially superior statistical properties in analyses of community composition compared to standard methods, but they simultaneously provide detailed information about species-specific responses underlying the changes in community composition.

Jones, J.A., Creed, I.F., Hatcher, K.L., Warren, R.J., Adams, M.B., Benson, M.H. Boose, E., Brown, W.A. Campbell, J.L., Covich, A., Clow, D.W., Dahm , C.N., Elder, K., Ford, C.R., Grimm , N.B., Henshaw, D.L., Larson, K.L., Miles, E.S., Miles, K.M., Sebestyen, S.D., Spargo, A.T., Stone, A.B., Vose, J.M., Williams, M.W., 2012. Ecosystem Processes and Human Influences Regulate Streamflow Response to Climate Change at LTER Sites. BioScience. Vol. 62:4, April 2012

Abstract
Analyses of long-term records at 35 headwater basins in the United States and Canada indicate that climate change effects on streamflow are not as clear as might be expected, perhaps because of ecosystem processes and human influences. Evapotranspiration was higher than was predicted by temperature in water-surplus ecosystems and lower than was predicted in water-deficit ecosystems. Streamflow was correlated with climate variability indices (e.g., the El Niño–Southern Oscillation, the Pacific Decadal Oscillation, the North Atlantic Oscillation), especially in seasons when vegetation influences are limited. Air temperature increased significantly at 17 of the 19 sites with 20- to 60-year records, but streamflow trends were directly related to climate trends (through changes in ice and snow) at only 7 sites. Past and present human and natural disturbance, vegetation succession, and human water use can mimic, exacerbate, counteract, or mask the effects of climate change on streamflow, even in reference basins. Long-term ecological research sites are ideal places to disentangle these processes.

Keitzer, S.C. and Reuben R. Goforth. 2012. Response of stream-breeding salamander larvae to sediment deposition in southern Appalachian (U.S.A.) headwater streams. Freshwater Biology 57(8):1535-1544.

Abstract
1. Increased fine sediment deposition is a prevalent threat to stream biodiversity and has been shown to impact stream-breeding salamanders negatively. However, their complex life histories make it difficult to determine which stage is affected. 2. We conducted field experiments from 26 August to 11 September 2010 and 11 October to 11 November 2010 in two southern Appalachian headwater streams (U.S.A.) to examine the response of larval salamanders to increased fine sediment deposition. Fine sediment was increased in artificial stream channels by 0, 33 and 67%. The number of larvae observed at the end of the experiments was used to determine whether larval microhabitat selection was influenced by fine sediment deposition. A concurrent survey of aquatic larvae in three nearby streams complemented this experiment. Stream substratum composition at survey sites was quantified to examine the effects of fine sediment on larval salamander abundance. 3. Increases in fine sediment deposition failed to explain the number of larval salamanders detected in stream channels. Similarly, a negligible effect of fine sediment was observed on abundance estimates. 4. These results suggest that fine sediment deposition has a minimal impact on aquatic salamander larvae. Therefore, the effects of increased fine sediment loads on stream-breeding salamanders may not be the result of deleterious effects on the aquatic larvae but instead may be the result of effects on other stages. Management efforts that consider these other stages are therefore needed to protect stream-breeding salamander communities.

Kirk, Ryan W., Bolstad, P.V., Manson, S.M., 2012, Spatio-temporal trend analysis of long-term development patterns (1900-2030) in a Southern Appalachian County, Landscape and Urban Planning 104(1):47-58

Abstract
Many mountainous areas in the U.S. have experienced significant changes in residential development patterns over the past century, in large part due to changing economies and in-migration from outsiders seeking the scenic resources of these areas. To evaluate changes in the Southern Appalachian mountain region, we reconstructed building and road locations in Macon County, North Carolina, since 1906 from historic maps, aerial photographs, county parcel records and emergency response program data. We used these data to analyze growth trends using spatio-temporal classification and quantile regression analysis. We also forecast future development patterns through 2030 using a multi-step model incorporating population growth projections, extrapolations of recent development density trends, and spatial logistic regression models. We characterize new development in the county as primarily rural from 1906 to 1960, exurban from 1960 to 1975 and increasingly suburban since 1975. While the rate of population growth and new building construction peaked in the 1980s, the total road length and rate of development in forested areas continued to increase from 1990 to 2009. We forecast that through 2030 approximately 75% of new buildings will be constructed at urban and suburban densities and that 67% of all new buildings will be constructed in forested areas. In addition to establishing the utility of using spatial analysis to draw together disparate data sources to understand urbanization over long time scales, this analysis identifies trends that have important implications for land-use planning, hydrology, forest management, and wildlife conservation.

Knapp, A.K., Smith, M.D., Hobbie, S.E., Collins, S.L., Fahey, T.J., Hansen, G.J.A., Landis, D.A., La Pierre, K.J., Melillo, J.M., Seastedt, T.R., Shaver, G.R., Webster, J.R., 2012. Past, Present, and Future Roles of Long-Term Experiments in the LTER Network. BioScience. Vol. 62:4, April 2012, p. 377-389, American Institute of Biological Sciences

Abstract
The US National Science Foundation–funded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have (a) provided unique insights into ecological patterns and processes, although such insight often became apparent only after many years of study; (b) influenced management and policy decisions; and (c) evolved into research platforms supporting studies and involving investigators who were not part of the original design. Furthermore, this suite of long-term experiments addresses, at the site level, all of the US National Research Council’s Grand Challenges in Environmental Sciences. Despite these contributions, we argue that the scale and scope of global environmental change requires a more-coordinated multisite approach to long-term experiments. Ideally, such an approach would include a network of spatially extensive multifactor experiments, designed in collaboration with ecological modelers that would build on and extend the unique context provided by the LTER Network.

Knoepp, Jennifer D., James M. Vose, Jerry L. Michael and Barbara C. Reynolds. 2012. Imidacloprid Movement in Soils and Impacts on Soil Microarthropods in Southern Appalachian Eastern Hemlock Stands in Journal of Environmental Quality 41:469-478.

Abstract
Imidacloprid is a systemic insecticide eff ective in controlling the exotic pest Adelges tsugae (hemlock woolly adelgid) in eastern hemlock (Tsuga canadensis) trees. Concerns over imidacloprid impacts on nontarget species have limited its application in southern Appalachian ecosystems. We quantifi ed the movement and adsorption of imidacloprid in forest soils after soil injection in two sites at Coweeta Hydrologic Laboratory in western North Carolina. Soils diff ered in profi le depth, total carbon and nitrogen content, and effective cation exchange capacity. We injected imidacloprid 5 cm into mineral soil, 1.5 m from infested trees, using a Kioritz soil injector. We tracked the horizontal and vertical movement of imidacloprid by collecting soil solution and soil samples at 1 m, 2 m, and at the drip line from each tree periodically for 1 yr. Soil solution was collected 20 cm below the surface and just above the saprolite, and acetonitrile-extractable imidacloprid was determined through the profile. Soil solution and extractable imidacloprid concentrations were determined by high-performance liquid chromatography. Soil solution and extractable imidacloprid concentrations were greater in the site with greater soil organic matter. Imidacloprid moved vertically and horizontally in both sites; concentrations generally declined downward in the soil profi le, but preferential fl ow paths allowed rapid vertical movement. Horizontal movement was limited, and imidacloprid did not move to the tree drip line. We found a negative relationship between adsorbed imidacloprid concentrations and soil microarthropod opulations largely in the low-organic-matter site; however, population counts were similar to other studies at Coweeta.

Kramer, Timothy D., Robert J. Warren II, Yaya Tang and Mark Bradford (2012) Grass Invasions Across a Regional Gradient are Associated with Declines in Belowground Carbon Pools (online document: http://www.springerlink.com/content/x70400184h168455/)

Abstract
The composition of plant communities everywhere now likely comprises alien as well as native species, and those aliens that become invasive have wide ranging impacts on the structure and function of recipient ecosystems. These impacts include perturbations to soil carbon (C) cycling, but the direction and magnitude of impacts are species and climate dependent, making it difficult to generalize whether a specific invader will promote losses or gains in soil C stocks. Generalizations of a specific invader’s impacts are necessary; however, because the range of an invader can encompass thousands of square kilometers, meaning their effects can have broad, regional consequences. To quantify broad-scale and context-dependent impacts of a specific invader, multi-site investigations that capture and measure local and regional environmental heterogeneity are necessary. Using this approach, we show that a widespread grass invader of forest understories is associated with declines in soil C during infilling (spreading within the invaded range). Across the 36 study sites, total soil C stocks declined (P = 0.113) by approximately 12% (estimated mean ± SD, uninvaded: 2,429 ± 512.9 vs. invaded: 2,140 ± 520.7 g C m-2). The decline in total soil C is driven by a significant (P = 0.047) reduction in the native-derived, mineral-associated soil C fraction. This fraction, whose mass and slow turnover makes it an important C store, is approximately 15% lower in invaded (estimated mean ± SD: 1,560 ± 400.4 g C m-2) than uninvaded plots (1,826 ± 398.1 g C m-2). Notably, declines in this C fraction are only apparent at 21 of the sites, reflecting how environmental heterogeneity in other variables (specifically pH, soil moisture, and clay content) are important to quantify to determine invader impacts across a region. The 26% decline in microbial biomass with invasion (P = 0.011; estimated mean ± SD, uninvaded: 10.05 ± 1.79 vs. invaded: 7.40 ± 1.80 g C m-2) is also dependent on site characteristics (pH), and reductions are greater where the invader occurs at higher densities. Reductions in microbial biomass and soil C with invasion suggest that grass invasion will alter soil C cycling and decrease forest-C stores across the study region, although invader effects at a specific-site will be dependent on environmental context.

Laseter, Stephanie H., Chelcy R. Ford, James M. Vose and Lloyd W. Swift Jr. 2012. Long-term temperature and precipitation trends at the Coweeta Hydrologic Laboratory, Otto, North Carolina, USA. Hydrology Research 43(6):890-901.

Abstract
Coweeta Hydrologic Laboratory, located in western North Carolina, USA, is a 2,185 ha basin wherein forest climate monitoring and watershed experimentation began in the early 1930s. An extensive climate and hydrologic network has facilitated research for over 75 years. Our objectives in this paper were to describe the monitoring network, present long-term air temperature and precipitation data, and analyze the temporal variation in the long-term temperature and precipitation record. We found that over the period of record: (1) air temperatures have been increasing significantly since the late 1970s, (2) drought severity and frequency have increased with time, and (3) the precipitation distribution has become more extreme over time. We discuss the implications of these trends within the context of regional and global climate change and forest health.

Li G., C.R. Jackson, and K.A. Kraseski. 2012. Published online. Modeled riparian stream shading: Agreement with field measurements and sensitivity to riparian conditions. Journal of Hydrology 428-429:142-151.

Abstract
Shading by riparian vegetation and streambanks reduces incident solar radiation on channels, and accurate estimation of riparian shading through the sun’s daily arc is a critical aspect of water temperature and dissolved oxygen modeling. However, riparian trees exhibit complex shapes, often leaning and growing branches preferentially over channels to utilize the light resource. As a result, riparian vegetation cast complex shadows with significant variability at the scale of meters. Water quality models necessarily simplify factors affecting shading at the expense of accuracy. All models must make simplifying assumptions about tree geometry. Reach-based models must average channel azimuth and riparian conditions over each reach, and GIS models must also accept errors in the channel-riparian relationships caused by the DEM grid detail. We detail minor improvements to existing shade models and create a model (SHADE2) that calculates shading ratio (%) by riparian canopy at any time and location for given stream characteristics including stream azimuth, stream width, canopy height, canopy overhang, and height of maximum canopy overhang. Sensitivity of simulated shade to these variables is explored. We also present a new field photographic technique for quantifying shade and use this technique to provide data to test the SHADE2 algorithm. Twenty-four independent shade measurements were made in eight channels with mature hardwood riparian trees at different times of the summer and at different times of the day. Agreement between measured and modeled shade was excellent, with r2 of 0.90.

Lin, L. and Webster, J.R. 2012. Sensitivity analysis of the pulse addition method for estimating nutrient uptake in large streams. Limnology and Oceanography: Methods. 10:718-727. (DOI: 10.4319/lom.2012.10.718)

Abstract
The constant nutrient addition technique has been used extensively to measure nutrient uptake in streams. However, this technique is impractical for large streams, and the pulse nutrient addition (PNA) has been suggested as an alternative. We developed a computer model to simulate Monod kinetics nutrient uptake in large rivers and used this model to evaluate the sensitivity of the PNA technique. We parameterize our model using the average hydrogeomorphological estimates from a pulse release study of ammonium in the Snake River, WY, and used this study to demonstrate how data from a field experiment can be effectively analyzed using a simulation model. To evaluate the sensitivity of the PNA technique, we manipulated the hydrogeomorphology and uptake kinetics of our stream model, simulated a pulse ammonium addition, and measured the downstream response in our model as if it were a field experiment, while ammonium areal uptake at ambient concentration was kept unchanged in the model. Ammonium uptake estimates by the PNA technique were different from the uptake in our model and these differences were nonrandom. The difference was greatest when velocity was high and there was little solute spread, either in the water column or from exchange with transient storage. The difference was also high when the half saturation coefficient for uptake was low. Our estimates of ammonium uptake under the assumption of Monod kinetics were higher than those under the assumption of first-order kinetics based on direct calculation from the experimental data.

Lumpkin, H., Pearson, S.M. and Turner, M.G. 2012. Climate and exurban development affect nest predation and nest predator presence in the Southern Appalachians. Conservation Biology. 26:679-688. (DOI: 10.1111/j.1523-1739.2012.01851.x)

Abstract
In the eastern United States, land-use and climate change have likely contributed to declines inthe abundance of Neotropical migrant birds that occupy forest interiors, but the mechanisms are not wellunderstood. We conducted a nest-predation experiment in southern Appalachian Mountain forests (NorthCarolina, U.S.A.) during the 2009 and 2010 breeding seasons to determine the effects of exurban developmentand temperature on predator presence and the average number of days until eggs in an artificial nest weredisturbed by predators. We baited artificial nests with quail ( Excalfactoria chinensi) eggs and monitoredthem for 18 days. We used clay eggs, track plates, and motion-triggered cameras to detect and identify nestpredators. The average number of days a nest was undisturbed decreased as mean temperature increasedand, to a lesser extent, as the density of buildings increased. Nests on the ground were more often depredatedthan those in trees, likely due to increased predation by opossum ( Didelphis virginiana) and other carnivores.Raccoons (Procyon lotor), opossums, corvids ( Corvus brachyrhynchos and Cyanocitta cristata), chipmunks( Tamias striatus), black bears ( Ursus americanus), and domestic cats ( Felis catus) were the most commonlydetected predators. Presence of these predators did not vary as a function of mean temperature. Domesticcats and corvids were detected more frequently in plots with high rather than low densities of buildings.Forest-interior specialists and Neotropical migrants often nest in cool, high-elevation areas with low housingdensity. These bird species, especially those that nest on the ground, may be most vulnerable to increased nestpredation if temperature and exurban development increase at higher elevations as anticipated

Moran, E. and Clark, J.S. 2012. Between-Site Differences in the Scale of Dispersal and Gene Flow in Red Oak. PLoS ONE. 7(5):e36492. (DOI: 10.1371/journal.pone.0036492)

Abstract
Background: Nut-bearing trees, including oaks (Quercus spp.), are considered to be highly dispersal limited, leading to concerns about their ability to colonize new sites or migrate in response to climate change. However, estimating seed dispersal is challenging in species that are secondarily dispersed by animals, and differences in disperser abundance or behavior could lead to large spatio-temporal variation in dispersal ability. Parentage and dispersal analyses combining genetic and ecological data provide accurate estimates of current dispersal, while spatial genetic structure (SGS) can shed light on past patterns of dispersal and establishment.Methodology and Principal Findings: In this study, we estimate seed and pollen dispersal and parentage for two mixed species red oak populations using a hierarchical Bayesian approach. We compare these results to those of a genetic ML parentage model. We also test whether observed patterns of SGS in three size cohorts are consistent with known site history and current dispersal patterns. We find that, while pollen dispersal is extensive at both sites, the scale of seed dispersal differs substantially. Parentage results differ between models due to additional data included in Bayesian model and differing genotyping error assumptions, but both indicate between-site dispersal differences. Patterns of SGS in large adults, small adults, and seedlings are consistent with known site history (farmed vs. selectively harvested), and with long-term differences in seed dispersal. This difference is consistent with predator/disperser satiation due to higher acorn production at the low-dispersal site. While this site-to-site variation results in substantial differences in asymptotic spread rates, dispersal for both sites is substantially lower than required to track latitudinal temperature shifts. Conclusions: Animal-dispersed trees can exhibit considerable spatial variation in seed dispersal, although patterns may be surprisingly constant over time. However, even under favorable conditions, migration in heavy-seeded species is likely to lag contemporary climate change.

Moran, E.V. and J.S. Clark. 2012. Causes and consequences of unequal seed production in forest trees: a case study in red oaks. Ecology. 93(5):1082-1094.

Abstract
Inequality in reproductive success has important implications for ecological and evolutionary dynamics, but lifetime reproductive success is challenging to measure in longlived species such as forest trees. While seed production is often used as a proxy for overall reproductive success, high mortality of seeds and the potential for trade-offs between seed number and quality draw this assumption into question. Parentage analyses of established seedlings can bring us one step closer to understanding the causes and consequences of variation in reproductive success. In this paper we demonstrate a new method for estimating individual seedling production and average percentage germination, using data from two mixed-species populations of red oaks (Quercus rubra, Q. velutina, Q. falcata, and Q. coccinea). We use these estimates to examine the distribution of female reproductive success and to test the relationship between seedling number and individual seed production, age, and growth rate. We show that both seed and seedling production are highly skewed, roughly conforming to zero-inflated lognormal distributions, rather than to the Poisson or negative-binomial distributions often assumed by population genetics analyses. While the number of established offspring is positively associated with mean annual seed production, a lower proportion of seeds from highly fecund individuals become seedlings. Our red oak populations also show evidence of trade-offs between growth rate and reproductive success. The high degree of inequality in seedling production shown here for red oaks, and by previous studies in other species, suggests that many trees may be more vulnerable to genetic drift than previously thought, if immigration in limited by fragmentation or other environmental changes.

Moran, E.V., J. Willis, and J.S. Clark. 2012. Genetic evidence for hybridization in red oaks. American Journal of Botany. 99(1):92-100.

Abstract
Premise of the study: Hybridization is pervasive in many plant taxa, with consequences for species taxonomy, local adaptation, and management. Oaks ( Quercus spp.) are thought to hybridize readily yet retain distinct traits, drawing into question the biological species concept for such taxa, but the true extent of gene fl ow is controversial. Genetic data are beginning to shed new light on this issue, but red oaks (section Lobatae ), an important component of North American forests, have largely been neglected. Moreover, gene fl ow estimates may be sensitive to the choice of life stage, marker type, or genetic structure statistic. Methods: We coupled genetic structure data with parentage analyses for two mixed-species stands in North Carolina. Genetic structure analyses of adults (including F ST , R ST , G ’ ST , and STRUCTURE ) refl ect long-term patterns of gene fl ow, while the percentage of seedlings with parents of two different species refl ect current levels of gene fl ow. Key results: Genetic structure analyses revealed low differentiation in microsatellite allele frequencies between co-occurring species, suggesting past gene fl ow. However, methods differed in their sensitivity to differentiation, indicating a need for caution when drawing conclusions from a single method. Parentage analyses identifed > 20% of seedlings as potential hybrids. The species examined exhibit distinct morphologies, suggesting selection against intermediate phenotypes. Conclusions: Our results suggest that hybridization between co-occurring red oaks occurs, but that selection may limit introgression, especially at functional loci. However, by providing a source of genetic variation, hybridization could infl uence the response of oaks and other hybridizing taxa to environmental change.

Norwood, C., Cumming. G., 2012. Making Maps That Matter: Situating GIS within Community Conversations about Changing Landscapes. Cartographica 47:1, 2012, University of Toronto Press, pp.2-17, doi:10.3138/carto.47.1.34

Abstract
Geospatial analysis and mapping has tremendous potential to inform community-scale deliberations about land use and growth management, but that potential is rarely realized. This article introduces an iterative, participatory research approach to generating maps about landscape change and development trends rooted in local experiences of place and therefore well positioned to contribute to civic dialogue and action. The research process involved collaboration with community partners; ethnographic interviews to identify salient local issues and perspectives; geospatial analysis, mapping, and visualizations of development trends; focus groups to refine information and imagery for local audiences; and deliberative meetings designed to encourage public discussion. Through a case study from a rapidly growing Southern Appalachian county, we show how this process aided the development of maps and visualizations that were relevant and accessible to local stakeholders, made visible local concerns about landscape change, and increased stakeholders’ awareness of landscape-scale processes. We argue that this interdisciplinary approach can help to bridge between critical and analytic GIS traditions, provide a mechanism for integrating research agendas with local policy deliberations, and help foster successful civic dialogues and collective action in communities with histories of contentious debate about land-use planning.

Robertson, G.P., Collins, S.L., Foster, D.R., Brokaw, N., Ducklow, H.W., Gragson, T.L., Gries, C., Hamilton, S.K., McGuire, A.D., Moore, J.C., Stanley, E.H., Waide, R.B., Williams, M.W., 2012. Long-Term Ecological Research in a Human-Dominated World. BioScience, Vol. 62:4, April 2012, p. 342-353, American Institute of Biological Sciences

Abstract
The US Long Term Ecological Research (LTER) Network enters its fourth decade with a distinguished record of achievement in ecological science. The value of long-term observations and experiments has never been more important for testing ecological theory and for addressing today’s most difficult environmental challenges. The network’s potential for tackling emergent continent-scale questions such as cryosphere loss and landscape change is becoming increasingly apparent on the basis of a capacity to combine long-term observations and experimental results with new observatory-based measurements, to study socioecological systems, to advance the use of environmental cyberinfrastructure, to promote environmental science literacy, and to engage with decisionmakers in framing major directions for research. The long-term context of network science, from understanding the past to forecasting the future, provides a valuable perspective for helping to solve many of the crucial environmental problems facing society today.

Serengil, Yusuf, Wayne T. Swank and James M. Vose. 2012. Alterations on flow variability due to converting hardwood forests to pine. iForest 5:44-49.

Abstract
Flow variability is a potential indicator of land use impacts on aquatic ecosystems and a dominating factor for lotic habitats. Vegetation management effects on the stream habitat conditions must be better understood to propose forest management activities that are compatible with general ecosystem management objectives (integrity, diversity, sustainability, etc.). In our study, we used long term flow data (1936-2004) from four gauged experimental watersheds (W1, W2, W17, W18) of Coweeta Hydrologic Laboratory in US to assess the impacts of pine conversion on flow characteristics by using paired watershed experimentation. In W1, all trees and shrubs were cut and burned in 1956-57 and white pine (Pinus strobus) was planted in 1957. In W17, white pine was planted in 1956. W2 and W18 have been kept untreated as reference watersheds for W1 and W17, respectively. After analyzing long-term daily flow series with flow duration curves and frequency analyzes, we found that the timing and magnitude of 7Q flows were changed significantly due to conversion but flow variability was not affected. Overall findings revealed that pine conversion has significantly influenced some flow characteristics but stream habitat conditions were not affected potentially.

Tang Yaya, Robert Warren III, Timothy Kramer, and Mark Bradford (2012) Plant invasion impacts on arthropod abundance, diversity and feeding consistent across environmental and geographic gradients. Biological Invasions:1-13. Online Version DOI: http://dx.doi.org/10.1007/s10530-012-0258-1.

Abstract
Exotic plant invasion not only changes native plant communities, it also alters associated arthropod community diversity and structure. These impacts often are contradictory and context-specific by study location. M. vimineum is an Asian grass currently invading the eastern United States that generally escapes herbivory. The invasion impacts on arthropod communities are mixed, and the effects on arthropod food webs are largely unknown. Because M. vimineum has a unique d13 C value, its carbon flow can be resolved from native plants in recipient food webs. We investigate arthropod communities at M. vimineum -invaded sites along a 100-km geographic and environmental gradient in the southeastern U.S. We investigate M. vimineum impacts on arthropod abundance and diversity, how M. vimineum -derived carbon contributes to arthropod biomass and how environmental variation modifies invasion effects on arthropod communities. We find that M. vimineum invasion corresponds with increased arthropod diversity and abundance, but reduced evenness. Herbivore damage to leaves is equivalent between native species and M. vimineum , but the type of herbivore damage is not the same between the native and invader plants. We also find that herbivores derive 37 % of their biomass-carbon from the exotic plant but predators almost none (4 %). Detritivores derive exotic carbon (9 %) proportional to M. vimineum in the litter layer. Whereas exotic plant impacts on arthropod communities often seem idiosyncratic by site, we find no context-dependent invasion effects of M. vimineum by study location. The consistency suggests that the impacts may be broadly generalizable, at least within well-established parts of the invasion range.

Tedela, N.H., McCutcheon, S.C., Campbell, J. L, Swank, W.T., Adams, M.B. and Rasmussen, T.C. 2012. Curve numbers for nine mountainous eastern United States watersheds: seasonal variation and forest cutting. Journal of Hydrologic Engineering. 17: 1199-1203. Journal of Hydrologic Engineering. 17:1199-1203.

Abstract
Many engineers and hydrologists use the curve number method to estimate runoff from ungaged watersheds; however, the method does not explicitly account for the influence of season or forest cutting on runoff. This study of observed rainfall and runoff for small, forested watersheds that span the Appalachian Mountains of the eastern United States showed that curve numbers calibrated for the growing season tended to be smaller than for the dormant season. Forest cutting tended to increase curve numbers. However, the increase in water yield following forest cutting on these watersheds only lasted 1 year to 11 years, thereby limiting the precision of the curve numbers estimated for these brief hydrologic effect periods. This study highlights the need to account for seasonal and forest cutting when estimating runoff from some forested watersheds.

Tran, T. and Elliott, K. 2012. Estimating Rhododendron maximum L. (Ericaceae) CanopyCover Using GPS/GIS Technology. Castanea. 77(4):303-317. (DOI: http://dx.doi.org/10.2179/12-014)

Abstract
In the southern Appalachians, Rhododendron maximum L. (Ericaceae) is a key evergreen understory species, often forming a subcanopy in forest stands. Little is known about the significance of R. maximum cover in relation to other forest structural variables. Only recently have studies used Global Positioning System (GPS) technology as a field-based method to map the perimeter of shrub patches as a means of estimating canopy cover. We assessed the viability of using GPS technology to accurately measure R. maximum canopy cover in mountainous terrain; and we compared canopy cover to other R. maximum abundance variables, forest structural attributes, and environmental factors. We selected forty 20 3 40 m permanent plots at Coweeta Hydrologic Laboratory in western North Carolina to employ a variety of methods (visual estimates, GPS, and x-y coordinate measurements) to estimate canopy cover of R. maximum within each plot. We found a positive relationship between the GPS method and the more accurate x-y coordinate measurements (r ¼ 0.967, p lt 0.001). We compared the GPS-derived estimates to other measures of R. maximum abundance and found positive relationships between cover and density (r2¼0.800, p lt 0.001), basal area (r2¼0.747, p lt 0.001), total biomass (r2¼0.761, p lt 0.001), and leaf area index (r2¼0.761, p lt 0.001). The GPS method is a reliable field-based technology to estimate evergreen canopy cover and it could be used to estimate more difficult to measure parameters of R. maximum, given the significant relationships found in this study.

Uriarte M., J. S. Clark, J. K. Zimmerman, L. S. Comita, J. Forero-Montaña, and J. Thompson. 2012. Multi-dimensional tradeoffs in species responses to disturbance: Implications for diversity in a subtropical forest. Ecology. 93(1):191-205

Abstract
Species employ diverse strategies to cope with natural disturbance, but the importance of these strategies for maintaining tree species diversity in forests has been debated. Mechanisms that have the potential to promote tree species coexistence in the context of repeated disturbance include life history trade-offs in colonization and competitive ability or in species' ability to survive at low resource conditions and exploit the temporary resource-rich conditions often generated in the wake of disturbance (successional niche). Quantifying these trade-offs requires long-term forest monitoring and modeling. We developed a hierarchical Bayes model to investigate the strategies tree species employ to withstand and recover from hurricane disturbance and the life history trade-offs that may facilitate species coexistence in forests subject to repeated hurricane disturbance. Unlike previous approaches, our model accommodates temporal variation in process error and observations from multiple sources. We parameterized the model using growth and mortality data from four censuses of a 16-ha plot taken every five years (1990–2005), together with damage data collected after two hurricanes and annual seed production data (1992–2005). Species' susceptibilities to hurricane damage as reflected by changes in diameter growth and fecundity immediately following a storm were weak, highly variable, and unpredictable using traditional life history groupings. The lower crowding conditions (e.g., high light) generated in the wake of storms, however, led to greater gains in growth and fecundity for pioneer and secondary-forest species than for shade-tolerant species, in accordance with expectation of life history. We found moderate trade-offs between survival in high crowding conditions, a metric of competitive ability, and long-distance colonization. We also uncovered a strong trade-off between mean species fecundity in low crowding conditions, a metric of recovery potential, and competitive ability. Trade-offs in competitive and colonization ability, in addition to successional niche processes, are likely to contribute to species persistence in these hurricane-impacted forests. The strategies species employ to cope with hurricane damage depend on the degree to which species rely on sprouting, repair of adult damage, changes in demographic rates in response to enhanced resource availability after storms, or long-distance dispersal as recovery mechanisms.

Wang, L. and Leigh, D.S. 2012. Late Holocene paleofloods in the Upper Little Tennessee River Valley, Southern Blue Ridge Mountains, USA. The Holocene, 22(9): 1061-1066. DOI: 10.1177/0959683612437863.

Abstract
We derive a paleoflood chronology for the past 2000 years from three stratigraphic sections of overbank sediments with dates from radiocarbon, luminescence, 137Cs techniques, and historical records. Particle sizes were measured in 6–15 year intervals in post-1870 sediments and in 45–170 year intervals in pre-1870 sediments using an automatic laser analyzer. The sedimentological characteristics of ad 1948–2009 deposits were compared with gaging records, demonstrating that fine sand content and sorting discern time intervals of large floods, but flood magnitudes are not well resolved. This modern analog was applied to pre-1870 sediments and revealed two periods in the last 2000 years with large floods during AD 650–850 and AD 1100–1350, which are times when the regional tree-ring record showed extreme wetness and no severe or extreme droughts. Our findings indicate flood-prone phases of transitional climate at the beginning and end of the ‘Medieval Warm Period’ (MWP), and relatively subdued flooding during the ‘Little Ice Age’ (LIA), possibly correlated with rearrangement of macro-scale atmospheric circulation patterns between the MWP and the LIA.

Warren, R.J, Giladi, I., Bradford, M.A. (2012) Environmental heterogeneity and interspecific interactions influence nest colonization by key seed-dispersing ants. Environmental Entomology, 41, 463-468.

Abstract
The complex interplay between species along environmental gradients ultimately shapes their distributions and additional community interactions. Ant-mediated seed dispersal fails in the wettest habitat of deciduous forest in eastern North America, and we examine whether this pattern corresponds with colony distributions for seed-dispersing ants and associated heterogeneity in abiotic and biotic variables. Specifically, we used spatial variation in soil moisture, temperature and diffuse light along natural habitat gradients and experimentally manipulated soil moisture gradients to examine ant habitat selection. We also examined niche segregation between effective (Aphaenogaster spp.) and ineffective (Lasius alienus Foerster) seed-dispersing ants across these environmental gradients. Whereas most research links ant foraging and nesting with temperature gradients, we find niche segregation between Aphaenogaster spp. and L. alienus by soil moisture along naturally occurring gradients and in experimentally irrigated upland habitat. The failure of Aphaenogaster spp. to occupy the wettest habitats, where L. alienus is present, is consistent with observed seed dispersal failure in these habitats. These results indicate that environmental heterogeneity drives niche segregation between effective (Aphaenogaster spp.) and ineffective (L. alienus) seed dispersers so each occupies distinct habitat. Most forest understory plants rely on ants for seed dispersal. Our research implies that climate-mediated interactions between effective and ineffective seed dispersing ant species may structure the microhabitat distributions for woodland herbs.

Warren, Robert J. and Jeffrey K. Lake. 2012. Trait plasticity, not values, best corresponds with woodland plant success in novel and manipulated habitats. Journal of Plant Ecology 1-12.

Abstract
Aims The clustering of plants with similar leaf traits along environmental gradients may arise from adaptation as well as acclimation to heterogeneous habitat conditions. Determining the forces that shape plant leaf traits requires both linking variation in trait morphology with abiotic gradients and linking that trait variation with plant performance under varying abiotic conditions. Across the spectrum of plant types, shade-tolerant evergreen herbs are relatively low in trait plasticity, compared to deciduous and sun-adapted species. These plants employ stress-tolerant strategies for survival, which coincide with relatively static trait morphologies, slow growth and hence a lower ability to adjust to changing environmental conditions. Methods We investigate how the survival of two ecologically similar understory evergreen species, Asarum arifolium and Hepatica nobilis, corresponds with variation in six commonly measured functional traits (leaf area, specific leaf area, plant height, leaf number, leaf length and shoot mass) along natural and experimental abiotic gradients. We examine temporal (the period 2007–9) and spatial (100 km) variations in these traits after (i) translocating 576 plants across a span from the southern Appalachian Mountains in NC, USA, to the Piedmont, GA, USA, which includes north- and south-facing slope habitats and (ii) the experimental manipulation of diffuse light and soil moisture. Important findings We find that when translocated into a novel habitats, with novel environmental conditions that often are more extreme than the source habitat, both species appear capable of considerable morphological acclimation and generally converge to similar trait values. Hepatica nobilis does not exhibit mean trait values particularly different from those of A. arifolium, but it demonstrates much greater phenotypic plasticity. These results indicate that relatively conservative plant species nonetheless acclimate and survive across heterogeneous environmental conditions.

Webster, J.R., K. Morkenski, C.A. Wojculewski, B.R. Niederlehner, E.F. Benefield and K.J. Elliott (2012). Effects of Hemlock Mortality on Streams in the Southern Appalachian Mountains. The Midland American Naturalist: An International Journal of Ecology, Evolution and Environment. 168:112-131.

Abstract
The death of eastern hemlock (Tsuga canadensis) trees in response to infestation by the introduced hemlock woolly adelgid (Adelges tsugae) may affect ecosystem processes and structure of streams. Prior to hemlock mortality, we documented the conditions of eight small streams and their associated riparian forests within the Appalachian Mountains of North Carolina, U.S.A. Hemlock was the dominant tree species on all riparian sites and was always associated with rhododendron (Rhododendron maximum). Significant trends of increasing canopy openness, increasing light to the streams and increasing annual temperature range were observed. Contributions of hemlock to litterfall, in-stream wood, and benthic organic matter were important at the beginning of the study, suggesting that the loss of hemlock may significantly modify the trophic dynamics and physical structure of southern Appalachian streams. Increased growth of rhododendron in response to hemlock mortality may compensate for the trophic influences of hemlock loss. However, because of rhododendron’s negative effect on growth of seedlings of other tree species, the greatest ecosystem impact of hemlock wooly adelgid may be more extensive rhododendron thickets within the riparian corridors of southern Appalachian streams.

Wu, W., Clark, J.S. and Vose, J.M. 2012. Application of a full hierarchical Bayesian model in assessing streamflow response to a climate change scenario at the Coweeta Basin, NC, USA. Journal of Resources and Ecology. 3(2):118-128. (DOI: http://dx.doi.org/10.5814/j.issn.1674-764x.2012.02.003)

Abstract
We have applied a full hierarchical Baysian (HB) model to simulate streamflow at the CoweetaBasin that drains western North Carolina, USA under a doubled CO2 climate scenario. The full HB modelcoherently assimilated multiple data sources and accounted for uncertainties from data, parameters andmodel structures. Full predictive distributions for streamflow from the Bayesian analysis indicate notonly increasing drought, with substantial decrease in fall and summer flows, and soil moisture content,but also increase in the frequency of flood events when they were fit with Generalized Extreme Value(GEV) distribution and Generalized Pareto Distribution (GPD) under this doubled CO2 climate scenariocompared to the current climate scenario. Full predictive distributions based on the hierarchical Bayesianmodel, compared to deterministic point estimates, is capable of providing richer information to facilitatedevelopment of adaptation strategy to changing climate for a sustainable water resource management.

Zhu, K., C.W. Woodall, and J.S. Clark. 2012. Failure to migrate: lack of tree range expansion in response to climate change. Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02571.x

Abstract
Tree species are expected to track warming climate by shifting their ranges to higher latitudes or elevations, but current evidence of latitudinal range shifts for suites of species is largely indirect. In response to global warming, offspring of trees are predicted to have ranges extend beyond adults at leading edges and the opposite relationship at trailing edges. Large-scale forest inventory data provide an opportunity to compare present latitudes of seedlings and adult trees at their range limits. Using the USDA Forest Service's Forest Inventory and Analysis data, we directly compared seedling and tree 5th and 95th percentile latitudes for 92 species in 30 longitudinal bands for 43 334 plots across the eastern United States. We further compared these latitudes with 20th century temperature and precipitation change and functional traits, including seed size and seed spread rate. Results suggest that 58.7% of the tree species examined show the pattern expected for a population undergoing range contraction, rather than expansion, at both northern and southern boundaries. Fewer species show a pattern consistent with a northward shift (20.7%) and fewer still with a southward shift (16.3%). Only 4.3% are consistent with expansion at both range limits. When compared with the 20th century climate changes that have occurred at the range boundaries themselves, there is no consistent evidence that population spread is greatest in areas where climate has changed most; nor are patterns related to seed size or dispersal characteristics. The fact that the majority of seedling extreme latitudes are less than those for adult trees may emphasize the lack of evidence for climate-mediated migration, and should increase concerns for the risks posed by climate change.

Bruce, R. 2011. COMMUNITY ASSEMBLY IN THE SALAMANDER GENUS DESMOGNATHUS. Herpetological Monographs, 25, 1-24. Retrieved from http://www.jstor.org/stable/41406828

Abstract
Abstract: In this paper, I present a model of community assembly in the salamander Desmognathus based on a survey of assemblage composition throughout the range of the genus. species of Desmognathus can be sorted into three life-history categories, namely, stream, streamside, forest, based on duration of the larval phase and a suite of other life-history and morphological traits correlated with habitat use of the several life-history stages. In most assemblages having all three life-categories, stream species are larger than streamside species, and the latter species are larger than species. An evaluation of the literature on interspecific competition and prédation (i.e., intraguild in Desmognathus indicates that these processes are important in structuring assemblages salamanders. Thus, niche assembly, as opposed to dispersal assembly (i.e., neutral model), seems to model of community assembly in Desmognathus. Only streamside species occur throughout the range genus, and these forms alone are found around the periphery of the range. One to three streamside form the base of extant assemblages of Desmognathus , with stream and forest species contributing more diverse assemblages of the southern Appalachian region. The maximum numbers are two streamside species, two or three stream species, and two forest species, although assemblages of more six species are undocumented. I suggest that the rapid evolutionary diversification in body size and life in Desmognathus that has generated the complex assemblages of this genus in the Appalachians has facilitated by a high level of life-history symmetry in these

Clark, J.S., D.M. Bell, M.H. Hersh, and L. Nichols. 2011. Climate change vulnerability of forest biodiversity: climate and resource tracking of demographic rates. Global Change Biology, 17, 1834-1849.

Abstract
Forest responses to climate change will depend on demographic impacts in the context of competition. Current models used to predict species responses, termed climate envelope models (CEMs), are controversial, because (i) calibration and prediction are based on correlations in space (CIS) between species abundance and climate, rather than responses to climate change over time (COT), and (ii) they omit competition. To determine the relative importance of COT, CIS, and competition for light, we applied a longitudinal analysis of 27 000 individual trees over 6–18 years subjected to experimental and natural variation in risk factors. Sensitivities and climate and resource tracking identify which species are vulnerable to these risk factors and in what ways. Results show that responses to COT differ from those predicted based on CIS. The most important impact is the effect of spring temperature on fecundity, rather than any input variable on growth or survival. Of secondary importance is growing season moisture. Species in the genera Pinus, Ulmus, Magnolia, and Fagus are particularly vulnerable to climate variation. However, the effect of competition on growth and mortality risk exceeds the effects of climate variation in space or time for most species. Because sensitivities to COT and competition are larger than CIS, current models miss the most important effects. By directly comparing sensitivity to climate in time and space, together with competition, the approach identifies which species are sensitive to climate change and why, including the heretofore overlooked impact on fecundity.

Clark, J.S., D.M. Bell, M.H. Hersh, M. Kwit, E. Moran, C. Salk, A. Stine, D. Valle, and K. Zhu. 2011. Individual-scale variation, species-scale differences: inference needed to understand diversity. Ecology Letters 14, 1273-1287.

Abstract
As ecological data are usually analysed at a scale different from the one at which the process of interest operates, interpretations can be confusing and controversial. For example, hypothesised differences between species do not operate at the species level, but concern individuals responding to environmental variation, including competition with neighbours. Aggregated data from many individuals subject to spatio-temporal variation are used to produce species-level averages, which marginalise away the relevant (process-level) scale. Paradoxically, the higher the dimensionality, the more ways there are to differ, yet the more species appear the same. The aggregate becomes increasingly irrelevant and misleading. Standard analyses can make species look the same, reverse species rankings along niche axes, make the surprising prediction that a species decreases in abundance when a competitor is removed from a model, or simply preclude parameter estimation. Aggregation explains why niche differences hidden at the species level become apparent upon disaggregation to the individual level, why models suggest that individual-level variation has a minor impact on diversity when disaggregation shows it to be important, and why literature-based synthesis can be unfruitful. We show how to identify when aggregation is the problem, where it has caused controversy, and propose three ways to address it.

Clark, J.S., P. Agarwal , D.M. Bell , P. Flikkema , A. Gelfand , X. Nguyen , E. Ward , and J. Yang. 2011. Inferential ecosystem models, from network data to prediction. Ecological Applications, 21,1523-1536.

Abstract
Recent developments suggest that predictive modeling could begin to play a larger role not only for data analysis, but also for data collection. We address the example of efficient wireless sensor networks, where inferential ecosystem models can be used to weigh the value of an observation against the cost of data collection. Transmission costs make observations “expensive”; networks will typically be deployed in remote locations without access to infrastructure (e.g., power). The capacity to sample intensively makes sensor networks valuable, but high-frequency data are informative only at specific times and locations. Sampling intervals will range from meters and seconds to landscapes and years, depending on the process, the current states of the system, the uncertainty about those states, and the perceived potential for rapid change. Given that intensive sampling is sometimes critical, but more often wasteful, how do we develop tools to control the measurement and transmission processes? We address the potential of data collection controlled and/or supplemented by inferential ecosystem models. In a given model, the value of an observation can be evaluated in terms of its contribution to estimates of state variables and important parameters. There will be more than one model applied to network data that will include as state variables water, carbon, energy balance, biogeochemistry, tree ecophysiology, and forest demographic processes. The value of an observation will depend on the application. Inference is needed to weigh the contributions against transmission cost. Network control must be dynamic and driven by models capable of learning about both the environment and the network. We discuss application of Bayesian inference to model data from a developing sensor network as a basis for controlling the measurement and transmission processes. Our examples involve soil moisture and sap flux, but we discuss broader application of the approach, including its implications for network design.

Clinton B, Maier C, Ford C, Mitchell R. 2011. Transient changes in transpiration, and stem and soil CO2 efflux in longleaf pine (Pinus palustris Mill.) following fire-induced leaf area reduction. Trees - Structure and Function1-11. doi:10.1007/s00468-011-0574-6

Abstract
In 20-year-old longleaf pine, we examined short-term effects of reduced live leaf area (AL) via canopy scorching on sap flow (Q; kg H2O h-1), transpiration per unit leaf area (EL; mm day-1), stem CO2 efflux (Rstem; lmol m-2 s-1) and soil CO2 efflux (Rsoil; lmol m-2 s-1) over a 2-week period during early summer. Rstem and Q were measured at two positions (1.3-m or BH, and base of live crown—BLC), and Rsoil was measured using 15 opensystem chambers on each plot. EL before and after treatment was estimated using Q measured at BLC with estimates of AL before and after scorching. We expected Q to decrease in scorched trees compared with controls resulting from reduced AL. We expected Rstem at BLC and BH and Rsoil to decrease following scorching due to reduced leaf area, which would decrease carbon supply to the stem and roots. Scorching reduced AL by 77%. Prior to scorching, Q at BH was similar between scorch and control trees. Following scorching, Q was not different between control and scorch trees; however, EL increased immediately following scorching by 3.5-fold compared to control trees. Changes in EL in scorched trees corresponded well with changes in VPD (D), whereas control trees appeared more decoupled

Davis J. M., Rosemond, A.D., Small, G.E., 2011. Increasing donor ecosystem productivity decreases terrestrial consumer reliance on a stream resource subsidy. Oecologia 167:3, Nov. 2011, p. 821-834 DOI 10.1007/s00442-011-2026-9

Abstract
Because nutrient enrichment can increase ecosystem productivity, it may enhance resource flows to adjacent ecosystems as organisms cross ecosystem boundaries and subsidize predators in recipient ecosystems. Here, we quantified the biomass and abundance of aquatic emergence and terrestrial spiders in a reference and treatment stream that had been continuously enriched with nitrogen and phosphorus for 5 years. Because we previously showed that enrichment increased secondary production of stream consumers, we predicted that aquatic emergence flux would be higher in the treatment stream, subsequently increasing the biomass and abundance of terrestrial spiders. Those increases were predicted to be greatest for spiders specializing on aquatic emergence subsidies (e.g., Tetragnathidae). By adding a 15Nstable isotope tracer to both streams, we also quantified nitrogen flow from the stream into the riparian community. Emergence biomass, but not abundance, was higher in the treatment stream. The average body size of emerging adult insects and the relative dominance of Trichoptera adults were also greater in the treatment stream. However, spider biomass did not differ between streams. Spiders also exhibited substantially lower reliance on aquatic emergence nitrogen in the treatment stream. This reduced reliance likely resulted from shifts in the body size distributions and community composition of insect emergence that may have altered predator consumption efficiency in the treatment stream. Despite nutrient enrichment approximately doubling stream productivity and associated cross ecosystem resource flows, the response of terrestrial predators depended more on the resource subsidy’s characteristics that affected the predator’s ability to capitalize on such increases.

Dehring, C.A., Chamblee, J.F., Colwell, P.F., Dehring, C. and Depken, C. 2011. The Effect of Conservation Activity on Surrounding Land Prices. Land Economics. 87(3):452-472.

Abstract
This paper presents an empirical analysis of the structure of land prices both before and after land conservation occurs. Using data describing 12 years of vacant land transactions in Buncombe County, North Carolina, we find that fee simple conservations, as opposed to conservation easements, occur in higher-priced areas, but that lower-valued parcels within these areas are selected for conservation. We find positive price effects from land conservation of 46%. This premium declines with distance from the conserved parcel but does so to a lesser extent with easements, perhaps suggesting the market�s perception that conservation easements are more permanent than parcels conserved in fee. (JEL H23, Q51)

Effects of water quality on Appalachian Elktoe mussels in the Little Tennessee River. 2011. Geological Society of America (GSA) : Boulder, CO, United States.

Abstract
Alasmidonta raveneliana, the Appalachian Elktoe, is a freshwater mussel currently listed as critically endangered. An effort to restore their populations began in the mid-1990s, when only two populations were known to exist. After hurricanes Ivan and Francis in 2004 both populations were reduced to critical numbers and have steadily declined; by 2006 populations in the Little Tennessee River decreased by 80%. A hypothesized reason for this decline is a reduction in sediment and/or water quality associated with a combination of sedimentation from land use changes, agricultural runoff, mining, and industrial discharges. Alterations in sediment and water quality, and their potential impact on biota, have been tested by examination of dissolved and particulate trace metal concentrations and water quality parameters indicating the suitability of habitat available for sufficient aquatic health. Over the 2010 water year, hydro labs were deployed at three monitoring sites along the Little Tennessee River to evaluate the aquatic habitat. Collection and analysis of water samples for total, particulate, and dissolved concentrations of selected trace metals through ion chromatography and ICP-MS analysis was accomplished and variations in total suspended and dissolved sediment loads were determined along with flood events from sediment sampling and water grab samples collected across the hydrograph. Mussel shell material collected between 1990-2010 was analyzed to determine threats and bioaccumulation during the time of population decline. Findings show levels of trace metals in the sediment well above probable effect thresholds, backed by diluted uptake in the shells, but with limited copper or ammonia currently found through pore-water investigations at bio-available levels. Sediment analysis coupled with cores taken from an impoundment along the water-course show trends suggesting an increasing source of sulfitic rich minerals. The deposition of newly eroded sediment exposed across the basin by recent development is believed to be contributing to the exposure of this aquatic environment to fresh sulfitic oxides compared with the highly eroded sulfides normally present in a naturally eroding environment.

Ford, C.R., Hubbard, R. M., and Vose, J.M. 2011. Quantifying structural and physiological controls on canopy transpiration of planted pine and hardwood stands in the southern Appalachians. Ecohydrology 4(2):183-195.

Abstract
Recent studies have shown that planted pine stands exhibit higher evapotranspiration (ET) and are more sensitive to climatic conditions compared with hardwood stands. Whether this is due to management and stand effects, biological effects or their interaction is poorly understood. We estimated growing season canopy- and sap flux scaled leaf-level transpiration (Ec and EL) in five major overstory species over 3 years. Four hardwood species, Liriodendron tulipifera, Carya spp., Quercus rubra and Quercus prinus, were measured in an unmanaged watershed. Pinus strobus was measured in an adjacent planted pine watershed. We hypothesized that (1) species would differ in EL and stomatal conductance (GS), and their relationship with vapour pressure deficit (D); and (2) differences in growing season ET between the stands would result primarily from the differences in interception (Ei). Growing season ET in the planted pine stand exceeded hardwood ET by twofold during all 3 years. Transpiration and Ei contributed similarly to the ET difference, suggesting that physiological differences were equally as important as structural factors to the overall difference in ET. Among species, mean EL and GS differed significantly, as did their relationship with D. EL and GS of oaks and hickories were least responsive to changing D, while L. tulipifera and P. strobus were most responsive. This species-level understanding of variation in EL and GS and their interactions with climatic driving variables has important implications for predicting watershed-level responses to stand management, species invasion and loss, and climate variability.

Ford, Chelcy R., Stephanie H. Laseter, Wayne T. Swank, and James M. Vose. 2011. Can forest management be used to sustain water-based ecosystem services in the face of climate change? Ecological Applications 21:2049-2067.

Abstract
Forested watersheds, an important provider of ecosystems services related to water supply, can have their structure, function, and resulting streamflow substantially altered by land use and land cover. Using a retrospective analysis and synthesis of long-term climate and streamflow data (75 years) from six watersheds differing in management histories we explored whether streamflow responded differently to variation in annual temperature and extreme precipitation than unmanaged watersheds. We show significant increases in temperature and the frequency of extreme wet and dry years since the 1980s. Response models explained almost all streamflow variability (adjusted R2 > 0.99). In all cases, changing land use altered streamflow. Observed watershed responses differed significantly in wet and dry extreme years in all but a stand managed as a coppice forest. Converting deciduous stands to pine altered the streamflow response to extreme annual precipitation the most; the apparent frequency of observed extreme wet years decreased on average by sevenfold. This increased soil water storage may reduce flood risk in wet years, but create conditions that could exacerbate drought. Forest management can potentially mitigate extreme annual precipitation associated with climate change; however, offsetting effects suggest the need for spatially explicit analyses of risk and vulnerability.

Fraterrigo, Jennifer M., Michael S. Strickland, Ashley D. Keiser, Mark A. Bradford. 2011. Nitrogen uptake and preference in a forest understory following invasion by an exotic grass. Oecologia. DOI:10.1007/s00442-011-2030-0

Abstract
Plant–soil interactions have been proposed as a causative mechanism explaining how invasive plant species impact ecosystem processes. We evaluate whether an invasive plant influences plant and soil-microbe acquisition of nitrogen to elucidate the mechanistic pathways by which invaders might alter N availability. Using a 15N tracer, we quantify diVerences in nitrogen uptake and allocation in communities with and without Microstegium vimineum, a shade-tolerant, C4 grass that is rapidly invading the understories of eastern US deciduous forests. We further investigate if plants or the microbial biomass exhibit preferences for certain nitrogen forms (glycine, nitrate, and ammonium) to gain insight into nitrogen partitioning in invaded communities. Understory native plants and M. vimineum took up similar amounts of added nitrogen but allocated it diVerently, with native plants allocating primarily to roots and M. vimineum allocating most nitrogen to shoots. Plant nitrogen uptake was higher in invaded communities due primarily to the increase in understory biomass when M. vimineum was present, but for the microbial biomass, nitrogen uptake did not vary with invasion status. This translated to a signiWcant reduction (P < 0.001) in the ratio of microbial biomass to plant biomass nitrogen uptake, which suggests that, although the demand for nitrogen has intensiWed, microbes continue to be eVective nitrogen competitors. The microbial biomass exhibited a strong preference for ammonium over glycine and nitrate, regardless of invasion status. By comparison, native plants showed no nitrogen preferences and M. vimineum preferred inorganic nitrogen species. We interpret our Wndings as evidence that invasion by M. vimineum leads to changes in the partitioning of nitrogen above and belowground in forest understories, and to decreases in the microbial biomass, but it does not aVect the outcome of plant–microbe–nitrogen interactions, possibly due to functional shifts in the microbial community as a result of invasion.

Hwang, T., C. Song, J.M. Vose, and L.E. Band. 2011. Topography-mediated controls on local vegetation phenology estimated from MODIS vegetation index. Landscape Ecology. DOI: 10.1007/s10980-011-9580-8.

Abstract
Forest canopy phenology is an important constraint on annual water and carbon budgets, and responds to regional interannual climate variation. In steep terrain, there are complex spatial variations in phenology due to topographic influences on microclimate, community composition, and available soil moisture. In this study, we investigate spatial patterns of phenology in humid temperate forest as a function of topography. Moderate-resolution imaging spectroradiometer (MODIS) vegetation indices are used to derive local patterns of topography-mediated vegetation phenology using a simple post-processing analysis and a non-linear model fitting. Elevation has the most explanatory power for all phenological variables with a strong linear relationship with mid-day of greenup period, following temperatures lapse rates. However, all other phenological variables show quadratic associations with elevation, reflecting an interaction between topoclimatic patterns of temperature and water availability. Radiation proxies also have significant explanatory power for all phenological variables. Though hillslope position cannot be adequately resolved at the MODIS spatial resolution (250 m) to discern impacts of local drainage conditions, extended periods of greenup/senescence are found to occur in wet years. These findings are strongly supported by previous field measurements at different topographic positions within the study area. The capability of detecting topography-mediated local phenology offers the potential to detect vegetation responses to climate change in mountainous terrain. In addition, the large, local variability of meteorological and edaphic conditions in steep terrain provides a unique opportunity to develop an understanding of canopy response to the interaction of climate and landscape conditions.

Hwang, Taehee, Conghe Song, Paul V. Bolstad, Lawrence E. Band. 2011. Downscaling real-time vegetation dynamics by fusing multi-temporal MODIS and Landsat NDVI in topographically complex terrain. Remote Sensing of Environment 115(10): 2499-2512. (DOI:10.1016/j.rse.2011.05.010)

Abstract
Canopy phenology is an important factor driving seasonal patterns of water and carbon exchange between land surface and atmosphere. Recent developments of real-time global satellite products (e.g., MODIS) provide the potential to assimilate dynamic canopy measurements with spatially distributed process-based ecohydrological models. However, global satellite products usually are provided with relatively coarse spatial resolutions, averaging out important spatial heterogeneity of both terrain and vegetation. Therefore, bias can result from lumped representation of ecological and hydrological processes especially in topographically complex terrain. Successful downscaling of canopy phenology to high spatial resolution would be indispensable for catchment-scale distributed ecohydrological modeling, aiming at understanding complex patterns of water, carbon and nutrient cycling in mountainous watersheds. Two downscaling approaches are developed in this study to overcome this issue by fusing multi-temporal MODIS and Landsat TM data in conjunction with topographic information to estimate high spatio-temporal resolution biophysical parameters over complex terrain. MODIS FPAR (fraction of absorbed photosynthetically active radiation) is used to provide medium spatial resolution phenology, while the variability of vegetation within a MODIS pixel is characterized by Landsat NDVI. The algorithms depend on the scale-invariant linear relationship between FPAR and NDVI, which is verified in this study. Downscaled vegetation dynamics are successfully validated both temporally and spatially with ground-based continuous FPAR and leaf area index measurements. Topographic correction during the downscaling process has a limited effect on downscaled FPAR products except for the period around the winter solstice in the study area.

Keiser, A.D., Strickland, M.S., Fierer, N., Bradford, M.A. (2011) The effect of resource history on the functioning of soil microbial communities is maintained across time. Biogeosciences, 8, 1477-1486 (Part of Special Feature – Biotic interactions and biogeochemical processes in the soil environment)

Abstract
Historical resource conditions appear to influence microbial community function. With time, historical influences might diminish as populations respond to the contemporary environment. Alternatively, they may persist given factors such as contrasting genetic 5 potentials for adaptation to a new environment. Using experimental microcosms, we test competing hypotheses that function of distinct soil microbial communities in common environments (H1a) converge or (H1b) remain dissimilar over time. Using a 6×2 (soil community inoculum×litter environment) full-factorial design, we compare decomposition rates in experimental microcosms containing grass or hardwood litter environments. After 100 days, communities that develop are inoculated into fresh litters and decomposition followed for another 100 days. We repeat this for a third, 100-day period. In each successive, 100-day period, we find higher decomposition rates (i.e. functioning) suggesting communities function better when they have an experimental history of the contemporary environment. Despite these functional gains, differences in decomposition rates among initially distinct communities persist, supporting the hypothesis that dissimilarity is maintained across time. In contrast to function, community composition is more similar following a common, experimental history. We also find that “specialization” on one experimental environment incurs a cost, with loss of function in the alternate environment. For example, experimental history of a grass-litter environment reduced decomposition when communities were inoculated into a hardwood-litter environment. Our work demonstrates experimentally that despite expectations of fast growth rates, physiological flexibility and rapid evolution, initial functional differences between microbial communities are maintained across time. These findings question whether microbial dynamics can be omitted from models of ecosystem processes if we 25 are to predict reliably global change effects on biogeochemical cycles.

Keitzer, S.C., Goforth, R., Pessier, A.P., Johnson, A.J., 2011. Survey for the Pathogenic Chytrid Fungus Batrachochytrium dendrobatidis in Southwestern North Carolina Salamander Populations, Journal of Wildlife Diseases, 47(2), 2011, pp. 455–458

Abstract
Batrachochytrium dendrobatidis is a fungal pathogen responsible for a potentially fatal disease of amphibians. We conducted a survey for B. dendrobatidis in the Appalachian Mountains of southwestern North Carolina, USA, from 10 June to 23 July 23 2009. Ventral skin swabs were collected from plethodontid salamanders (n5278) and real-time PCR was performed to test for the presence of B. dendrobatidis. We found no evidence of B. dendrobatidis, suggesting that B. dendrobatidis is absent or present in such low levels that it was undetected. If B. dendrobatidis was present at the time of our sampling, this survey supports evidence of low prevalence of B. dendrobatidis in North American headwater stream salamander populations.

Knoepp, J.D., Vose, J.M. and Clinton, B.D. 2011. Hemlock Infestation and Mortality: Impacts on Nutrient Pools and Cycling in Appalachian Forests. Soil Science Society of America Journal. 75(5):1-11. (DOI: 10.2136/sssaj2010.0409)

Abstract
Eastern hemlock [Tsuga canadensis (L.) Carri�re] trees serve an important ecological role in riparian ecosystemsin the southern Appalachians. Significant hemlock mortality is occurring due to infestation by the hemlock woollyadelgid (HWA) (Adelges tsugae Annand), a non-native invasive pest. Our objective was to quantify the impactsof HWA and hemlock mortality on nutrient cycling pools and processes. In 2004, we established eight researchplots in riparian areas with >50% basal area in hemlock and four reference plots in riparian areas without hemlock(hardwood). All hemlock plots were infested with HWA. In four of the hemlock plots, all hemlock trees weregirdled to induce defoliation and rapid mortality. By fall 2006, there was 90 and 10% mortality in the girdled andnongirdled hemlock plots, respectively. Measurements included soil temperature and moisture, nutrient pools,N transformations, litterfall and forest floor amount and chemistry, and throughfall and soil solution chemistry.From 2004 to 2008, litterfall composition changed, with an initial increase in the hemlock needle percentagefollowed by a decline. Hemlock plots had cooler spring soil temperatures than hardwood plots. Hemlock plotshad greater surface soil and forest floor total C than hardwood plots; soil C content did not change during the 4yr of measurement. There were no differences in N mineralization rates or soil solution N concentrations amongtreatments. Differences between litterfall and forest floor nutrient contents in hemlock and hardwood plots suggestthat as hemlocks are replaced by hardwood species, nutrient cycling rates and processes will be similar tohardwood reference plots.

Kuhman, T.R., Pearson, S.M. and Turner, M.G. 2011. Agricultural land-use history increases non-nativeplant invasion in a southern Appalachian forest acentury after abandonment. Canadian Journal of Forest Research. 41(5):920-929.

Abstract
Land-use history can play a significant role in shaping forest communities. We considered the effects of agricultural land-use legacies on the distribution of non-native invasive plants a century after abandonment in a watershed in western North Carolina, USA. Forest sites that were previously in cultivation and abandoned ca. 1905 were compared with nearby reference sites that were never cultivated. The most common invasive plants were Celastrus orbiculatus Thunb., Microstegium vimineum Trin., and Lonicera japonica Thunb. Formerly cultivated sites and plots positioned downslope from roads had the most invasives. Soil cation concentration and pH were positively correlated with invasive presence and abundance. Historic agricultural plots where the successional tree Liriodendron tulipifera L. was dominant had the highest soil cation concentrations and soil pH and the greatest abundance of invasive plants. Disentangling the cause�effect relationships between land-use history, the biotic community, and the abiotic template presents a challenge, but understanding the role of land-use legacies may provide important insights regarding the mechanisms underlying the establishment and spread of invasive plants in forest ecosystems. Our results suggest that land-use history at Bent Creek may be facilitating plant invasion indirectly by causing a shift in overstory community composition that in turn creates more suitable understory conditions for shade-tolerant invasive plants

Lumpkin, H., Pearson, S.M. and Turner, M.G. 2011. Effects of climate and exurban development on nest predation and predator presence in the southern Appalachian mountains (U.S.A.). Conservation Biology. 26(4):679-688. (DOI: 10.1111/j.1523-1739.2012.01851.x)

Abstract
In the eastern United States, land-use and climate change have likely contributed to declines in the abundance of Neotropical migrant birds that occupy forest interiors, but the mechanisms are not well understood. We conducted a nest-predation experiment in southern Appalachian Mountain forests (North Carolina, U.S.A.) during the 2009 and 2010 breeding seasons to determine the effects of exurban development and temperature on predator presence and the average number of days until eggs in an artificial nest were disturbed by predators. We baited artificial nests with quail ( Excalfactoria chinensi) eggs and monitored them for 18 days. We used clay eggs, track plates, and motion-triggered cameras to detect and identify nest predators. The average number of days a nest was undisturbed decreased as mean temperature increased and, to a lesser extent, as the density of buildings increased. Nests on the ground were more often depredated than those in trees, likely due to increased predation by opossum ( Didelphis virginiana) and other carnivores. Raccoons (Procyon lotor), opossums, corvids ( Corvus brachyrhynchos and Cyanocitta cristata), chipmunks ( Tamias striatus), black bears ( Ursus americanus), and domestic cats ( Felis catus) were the most commonly detected predators. Presence of these predators did not vary as a function of mean temperature. Domestic cats and corvids were detected more frequently in plots with high rather than low densities of buildings. Forest-interior specialists and Neotropical migrants often nest in cool, high-elevation areas with low housing density. These bird species, especially those that nest on the ground, may be most vulnerable to increased nest predation if temperature and exurban development increase at higher elevations as anticipated.

Luo,Y. K. Ogle, C. Tucker, S. Fei, C, Gao, S. Ladeau, J. S. Clark, and D. S. Schimel. 2011. Ecological forecasting and data assimilation in a data-rich era. Ecological Applications 21, 1429–1442.

Markwith, Scott ; Leigh, David 2011. Comparison of estimated and experimental subaqueous seed transport. Ecohydrology.

Abstract
We compare the estimates from the relative bed stability (RBS) equation that indicates incipient bed movement, and the inertial settling (‘Impact’) law and Wu and Wang (2006) settling velocity equations that indicate suspended particle movement, to flume and settling velocity observations to confirm the utility of the equations for subaqueous hydrochory analyses, and to calibrate our estimates by examining the method by which seed volume is obtained. Comparison of the observed measures with the estimates of the inertial settling (‘Impact’) law and RBS equations indicate that these two equations appear to provide reasonable approximations of the velocities required to achieve transport both in suspension and on the bed, respectively. The use of the water displacement method for volume measurement is a technologically simple method for improving the accuracy of the estimates.

McDonald, J.M., Leigh, D.S. 2011. Terminal Pleistocene through Holocene Evolution of Whiteoak Bottoms, a Southern Blue Ridge Mountains Peatland. Wetlands, 31 (4), 783-797

Abstract
Our primary objective was to develop an understanding of the geomorphic evolution of Whiteoak Bottoms (WOB), a peatland along the Nantahala River in the Southern Blue Ridge Mountains (SBRM) of western North Carolina. Radiocarbon dates directly above basal fluvial sediments returned ages of 14,000 to 15,000 cal yr BP. These ages indicate WOB is the oldest dated peatland in the SBRM and that such wetlands have persisted throughout the Holocene. Below the relatively flat surface of the wetland, paleochannels, similar to those of the modern channel, were found; suggesting a persistence of similar channel morphology since the terminal Pleistocene. The wetland’s stratigraphy reveals a consistent pattern with basal fluvial cobbles being overlain by sandy channel-fill grading up into peat. Two different distinct inorganic deposits separate the lower organic deposits from the sapric peat deposits at the surface. Interestingly, we estimate more than 56% of the organic matter preserved by the wetland accumulated during the first 6,000 years of development. Overall, WOB has accumulated approximately 424 Mg/ha of carbon during the past 15,000 years. Maintenance of this wetland initially depended on the Nantahala River; however, today it is ground water and beavers that allows for the persistence of this rare landscape

McManamay, R.A., J.R. Webster, H.M. Valett, and C.A. Dolloff. 2011. Does diet influence consumer nutrient cycling? Examining macroinvertebrate and fish excretion in streams. Journal of the North American Benthological Society 30(1):84-102.

Abstract
Consumer nutrient cycling supplies limiting elements to autotrophic and heterotrophic organisms in aquatic systems. However, the role of consumers in supplying nutrients may change depending on their diet and their own stoichiometry. We evaluated the stoichiometry, N and P excretion, and diets of the dominant macroinvertebrates and fish at 6 stream sites to determine if the nutritional composition of food alters nutrient excretion. We used Sterner’s (1990) nutrient homeostasis model as a reference to gauge whether consumer nutrient excretion is influenced by diet. Body stoichiometry explained 61% of the variation in N:P excretion by macroinvertebrates but only 11% of the variation for fish. In both cases, the relationship was driven by 2 P-rich end-members, crayfish and mottled sculpin. Results of Akaike Information Criterion (AIC) analysis showed that family alone explained 71% of the variation in N:P excretion in macroinvertebrates and 31% of the variation in fish. Diet explained only 8% of the variation in both cases. Most consumers (9 of 11) had N:P excretion values that were well below predictions of Sterner’s model. Two taxa, crayfish and sculpin, had N:P excretion that overlapped the model’s predictions. Our results suggest that crayfish and sculpin may display strict homeostasis with respect to N and P and that their growth might be P-limited. Other consumers may be more flexible in their stoichiometry and not P-limited. We speculate that the extremely low excretion N:P measured for many consumers might have been the result of semiflexible homeostasis, inaccuracies in our assessment of dietary nutrients, growth-limiting nutrients other than N or P, or lack of egestion data. Our results suggest that crayfish and sculpin may alter N and P dynamics in streams by excreting low amounts of P relative to N compared to what is generally available in the water column.

Moran, Emily V. and James S. Clark. 2011. Estimating seed and pollen movement in a monoecious plant: a hierarchical Bayesian approach integrating genetic and ecological data. Molecular Ecology 20:1248-1262.

Abstract
The scale of seed and pollen movement in plants has a critical influence on population dynamics and interspecific interactions, as well as on their capacity to respond to environmental change through migration or local adaptation. However, dispersal can be challenging to quantify. Here, we present a Bayesian model that integrates genetic and ecological data to simultaneously estimate effective seed and pollen dispersal parameters and the parentage of sampled seedlings. This model is the first developed for monoecious plants that accounts for genotyping error and treats dispersal from within and beyond a plot in a fully consistent manner. The flexible Bayesian framework allows the incorporation of a variety of ecological variables, including individual variation in seed production, as well as multiple sources of uncertainty. We illustrate the method using data from a mixed population of red oak (Quercus rubra, Q. velutina, Q. falcata) in the NC piedmont. For simulated test data sets, the model successfully recovered the simulated dispersal parameters and pedigrees. Pollen dispersal in the example population was extensive, with an average father–mother distance of 178 m. Estimated seed dispersal distances at the piedmont site were substantially longer than previous estimates based on seed-trap data (average 128 m vs. 9.3 m), suggesting that, under some circumstances, oaks may be less dispersal-limited than is commonly thought, with a greater potential for range shifts in response to climate change.

Negussie H. Tedela, Steven C. McCutcheon, Todd C. Rasmussen, Richard H. Hawkins, Wayne T. Swank, John L. Campbell, Mary Beth Adams, C. Rhett Jackson, and Ernest W. Tollner, 2011. Runoff Curve Numbers for Ten, Small Forested Watersheds in the Mountains of the Eastern U.S. Journal of Hydrologic Engineering. Published online May 21, 2011.

Abstract
Engineers and hydrologists use the curve number method to estimate runoff from rainfall for different land use and soil conditions; however, large uncertainties occur for estimates from forested watersheds. This investigation evaluates the accuracy and consistency of the method using rainfall-runoff series from ten small, forested-mountainous watersheds in the eastern U.S., eight annual maximum series from New Hampshire, West Virginia, and North Carolina, and two partial duration series from Georgia. These series are the basis to compare tabulated curve numbers with values estimated using five methods. For nine of ten watersheds, tabulated curve numbers do not accurately estimate runoff. One source of the large uncertainty is a consistent decrease in runoff with increasing rainfall when deriving a constant curve number for a watershed. A calibrated constant curve number is suitable for only two of ten watersheds; the others require a variable watershed curve number associated with different magnitude rainfalls or probabilities of occurrence. Paired watersheds provide consistent curve numbers, indicating that regional values for forested-mountainous watersheds (locally calibrated and adjusted for storm frequency) may be feasible.

Peterman, William E., Crawford, J.A., Semlitsch, R.D., 2011. Effects of even-aged timber harvest on stream salamanders: Support for the evacuation hypothesis, Forest Ecology and Management, August 2011, vol 262, p. 2344-2353

Abstract
Habitats worldwide are increasingly threatened by degradation and conversion. Critical to the process of habitat loss is the organismal response, which can have effects on immediate conservation measures or future restoration. Among the most threatened and underappreciated habitats are headwater streams, which are small but abundant features of montane forests. These habitats comprise a significant proportion of the total stream length, can harbor remarkable biodiversity, and are critical for numerous ecosystem processes. One of the most abundant organisms in montane headwater ecosystems are salamanders, and therefore what happens to salamanders when the forest habitats surrounding headwater streams are altered? Three main hypotheses exist: (1) mortality hypothesis; (2) retreat hypothesis; and (3) evacuation hypothesis. To examine these hypotheses we evaluated the impacts of even-aged riparian timber harvest on stream-breeding salamanders. Riparian forests along headwater streams were logged, leaving riparian buffers of 0 m, 9 m, and 30 m. Responses to each riparian alteration were measured in terms of salamander terrestrial habitat use and growth in the riparian habitat, as well as changes in population density within headwater streams. Adult and juvenile salamander densities measured in headwater streams were significantly greater in logged riparian treatments than in unaltered riparian treatments. In addition, salamanders significantly reduced their terrestrial habitat use following riparian logging with both the average distance from the stream and the relative abundance of salamanders decreasing. It is unlikely that salamanders will persist in highly modified riparian habitats, as we measured significantly reduced body conditions over short periods of time at these sites. We present corroborative evidence that salamanders evacuate the riparian habitat following intensive riparian logging, emigrating to adjacent headwater streams. Our results underscore the sensitivity of stream salamanders to riparian habitat alteration as well as the importance of riparian buffers in preserving amphibian assemblages.

Price K., C.R. Jackson, A.J. Parker, T. Reitan, J. Dowd, and M. Cyterski. 2011. Effects of watershed land use and geomorphology on stream low flows during severe drought conditions in the southern Blue Ridge Mountains, Georgia and North Carolina, USA. Water Resources Research, 47 (W02516).

Abstract
Land use and physiographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the influence of land use and watershed geomorphic characteristics on low flow variability in the southern Blue Ridge Mountains of North Carolina and Georgia. Ten-minute interval discharge data for 35 streams (in watersheds from 3 to 146 km2) were measured for two late-summer low flow seasons, coinciding with a severe drought period in the southeastern United States. Three low flow metrics were calculated (1-day and 7-day minimum flows, and 1-percentile flow) for each low flow season (August 5-November 12, 2007 and August 1 – November 12, 2008). A comprehensive suite of watershed characteristics, including factors of topography, channel network morphometry, soils, land use, and precipitation were used in multiple regression analysis of low flow variability among the 35 watersheds. Additionally, low flows in groups of lower- and higher-forest cover watersheds were compared. Drainage density, areal coverage of colluvium, topographic variability (as slope standard deviation), and percent of the channel network as first order stream emerged as the most important variables for explaining low flow variability. Watershed forest cover demonstrated a consistent, significant positive relationship with low flows, despite the higher evapotranspiration rates associated with forest compared with other land covers, and despite the relatively small range of disturbance in this study area. This highlights the importance of infiltration and recharge under undisturbed land cover in sustaining low flows, and bears noteworthy implications for environmental flows and water resource sustainability.

Price, K. 2011. Effects of watershed topography, soils, land use, and climate on baseflow hydrology in humid regions: A review. Progress in Physical Geography 35(4):465-492.

Abstract
Baseflow is the portion of streamflow that is sustained between precipitation events, fed to stream channels by delayed (usually subsurface) pathways. Understanding baseflow processes is critical to issues of water quality, supply, and habitat. This review synthesizes the body of global literature investigating relationships between baseflow and watershed characteristics of geomorphology, soil, and land use, as well as the potential effects of climate change, with an emphasis on humid, tropical and temperate (non-snowpackdominated) regions. Such factors are key controls on baseflow through their influence on infiltration, rates of water removal from the catchment, and subsurface storage properties. The literature shows that there is much that remains to be resolved in gaining a solid understanding of the influence of watershed characteristics on baseflow. While it is clear that watershed geomorphology influences baseflow, there is no consensus on which geomorphic parameters are most closely linked to subsurface storage and baseflow. Many studies associate higher watershed forest cover with lower baseflows, attributed to high evapotranspiration rates of forests, while other studies indicate increased baseflow with higher watershed forest cover due to higher infiltration and recharge of subsurface storage. The demonstrated effects of agriculture and urbanization are also inconsistent, due to varied additions of imported water and extremely variable background conditions. This review underscores the need for more research that addresses multiple aspects of the watershed system in explaining baseflows, and for methodological consistency to allow for more fruitful comparisons across case studies. These needs are of immediate demand, given scientific and management emphasis on environmental flows required for maintenance of key ecosystem services. [ABSTRACT FROM PUBLISHER]

Rao, L.Y., Sun, G., Ford, C.R., and Vose, J.M, 2011. Modeling potential evapotranspiration of two forested watersheds in the southern Appalachians. Transactions of the American Society of Agricultural and Biological Engineers, 54(6): 2067-2078.

Abstract
Global climate change has direct impacts on watershed hydrology through altering evapotranspiration (ET) processes at multiple scales. There are many methods to estimate forest ET with models, but the most practical and the most popular one is the potential ET (PET) based method. However, the choice of PET methods for AET estimation remains challenging. This study explored ways to identify appropriate PET models for two small forested watersheds, one dominated by conifer plantation and one dominated by native naturally regenerated deciduous hardwoods, by using long-term hydrometeorological data collected at the Coweeta Hydrologic Laboratory in the humid Appalachians in the southeastern U.S. Our specific objectives were to: (1) contrast three common PET models (FAO-56 grass reference ET, Hamon PET, and Priestley-Taylor PET) and compare these PET estimates with measured AET at monthly and annual temporal scales, and (2) derive correction factors for the FAO-56 grass reference ET and Hamon PET models at the monthly scale using the Priestley-Taylor equation as the standard method for estimating forest PET. We found that different PET models gave significantly different PET estimates. The Priestley-Taylor equation gave the most reasonable estimates of forest PET for both watersheds. We conclude that the uncorrected Hamon and FAO PET methods would cause large underestimates of forest PET. Annual PET rates of the conifer watershed were higher than those of the native deciduous watershed due to the lower albedo (thus higher net radiation) in the former compared to the latter. Monthly correction factors provided useful tools for forest PET estimation in those areas lacking climatic data (i.e., radiation, humidity, and wind speed).

Serengil, Yusuf, Wayne T. Swank, Mark S. Riedel and James M. Vose. 2011. Conversion to pine: Changes in timing and magnitude of high and low flows. Scandinavian Journal of Forest Research 26(6):568-575.

Abstract
Understanding watershed responses to extreme events is important for assessing potential impacts of floods, droughts, episodic pollution, and other external driving variables on watershed resources. In this study, we combine trend and frequency analyses with paired watershed techniques to evaluate the long-term high- and low-flow data from Coweeta Hydrologic Laboratory in North Carolina, USA in an attempt to quantify and interpret responses to extreme flow events in managed and unmanaged watersheds. Two experimental watersheds were converted from mixed deciduous forest cover to pine (Pinus strobus L.) in 1957 and 1956, respectively and two others were kept untreated to serve as control watersheds. Seventy years of annual streamflow (instantaneous maximum, minimum, and mean) time series data from watersheds 1, 2, 17, and 18 were analyzed with a Mann Whitney Pettitt test to identify and compare change points. Mean annual streamflow increased in both watersheds for 10 12 years after harvests, but the more effective factor on the flow series was the growth of pine plantations. Maximum flows of 2-, 5-, and 10-year return periods decreased after planting pine, but there was no difference for larger flow events compared to deciduous forest. For minimum flows, pine stands were more effective compared to maximum flows as minimum flows decreased for all return periods.

Sokol ER, Benfield EF, Belden LK, Valett HM (2011) The assembly of ecological communities inferred from taxonomic and functional composition. The American Naturalist 177(5): 630-644. doi:10.1086/659625

Abstract
Among-site variation in metacommunities (beta diversity) is typically correlated with the distance separating the sites (spatial lag). This distance decay in similarity pattern has been linked to both niche-based and dispersal-based community assembly hypotheses. Here we show that beta diversity patterns in community composition, when supplemented with functional-trait information, can be used to diagnose assembly processes. First, using simulated data, we show how the relationship between distance decay patterns in taxonomic and functional measures of community composition can be used to predict the influence of a given trait on community assembly. We then use the patterns generated by the simulation as a template to show that the sorting of benthic macroinvertebrate metacommunities in headwater streams is likely influenced by different sets of functional traits at regional and local scales. We suggest that functional-trait databases and spatially referenced taxonomic surveys can be used to predict the spatial scales at which different aspects of interspecific functional variation are involved in niche-based community assembly while accounting for the influence of dispersal-based community assembly processes.

Strickland, M.S., Devore, J.L., Maerz, J.C., Bradford, M.A. (2011) Loss of faster-cycling soil carbon pools following grass invasion across multiple forest sites. Soil Biology & Biochemistry, 43, 452-454.

Abstract
It is established that invasive plant species can alter soilcarboncycling, although data are rare for late successional ecosystems. We examined effects of a grass invader (Microstegium vimineum) on soilcarbonacross eight sites in southeastern U.S. forests to establish which factors are related to these effects, by coupling isotopic and soilcarbon fractionation approaches. Invasion was associated with declines in mass of faster-cycling, particulate organic matter (POM) carbonpools. This led to a significant decline (11% on average) in native-derived carbon in the surface 10 cm of the soil profile. Formation of soilcarbon from the invader-derived inputs partially mitigated these losses (total carbonloss 6% on average). Our data suggest that Microstegiuminvasion of forest understories may accelerate carboncycling and could result in a net loss of soilcarbon from eastern U.S. forests.

Sun, G., Alstad, K., Chen, J., Chen, S., Ford, C.R., Lin, G., Lu, N., McNulty, S.G., Noormets, A., Vose, J.M., Wilske, B., Zeppel, M., Zhang, Y., and Zhang, Z., 2011. Modeling monthly evapotranspiration of thirteen ecosystems across a climatic and management gradient. Ecohydrology 4(2):245-255.

Sun, G., K. Alstad, J. Chen, S. Chen, C. R. Ford, G. Lin, C. Liu, N. Lu, S. G. McNulty, H. Miao, A. Noormets, J. M. Vose, B. Wilske, M. Zeppel, Y. Zhang, Z. Zhang. 2011. A general predictive model for estimating monthly ecosystem evapotranspiration. Ecolohydrology, 4: 245-255.

Abstract
Accurately quantifying evapotranspiration (ET) is essential for modelling regional-scale ecosystem water balances. This study assembled an ET data set estimated from eddy flux and sapflow measurements for 13 ecosystems across a large climatic and management gradient from the United States, China, and Australia. Our objectives were to determine the relationships among monthly measured actual ET (ET), calculated FAO-56 grass reference ET (ETo), measured precipitation (P), and leaf area index (LAI)—one associated key parameter of ecosystem structure. Results showed that the growing season ET from wet forests was generally higher than ETo while those from grasslands or woodlands in the arid and semi-arid regions were lower than ETo. Second, growing season ET was found to be converged to within š10% of P for most of the ecosystems examined. Therefore, our study suggested that soil water storage in the nongrowing season was important in influencing ET and water yield during the growing season. Lastly, monthly LAI, P, and ETo together explained about 85% of the variability of monthly ET. We concluded that the three variables LAI, P, and ETo, which were increasingly available from remote sensing products and weather station networks, could be used for estimating monthly regional ET dynamics with a reasonable accuracy. Such an empirical model has the potential to project the effects of climate and land management on water resources and carbon sequestration when integrated with ecosystem models.

Vose, J. M., G. Sun, C. R. Ford, M. Bredemeier, K. Ostsuki, A. Wei, Z. Zhang, and L. Zhang. 2011. Forest ecohydrologial research in the 21st century: what are the critical needs?. Published online. Ecohydrology, DOI: 10.1002/eco.193.

Abstract
Modern ecohydrologic science will be critical for providing the best information to policy makers and society to address water resource challenges in the 21st century. Implicitly, ecohydrology involves understanding both the functional interactions among vegetation, soils, and hydrologic processes at multiple scales and the linkages among upland, riparian, and aquatic components. In this paper, we review historical and contemporary ecohydrologic science, focusing on watershed structure and function and the threats to watershed structure and function. Climate change, land use change, and invasive species are among the most critical contemporary issues that affect water quantity and quality, and a mechanistic understanding of watershed ecosystem structure and function is required to understand their impacts on water quantity and quality. Economic and social values of ecosystem services such as water supply from forested watersheds must be quantified in future research, as land use decisions that impact ecohydrologic function are driven by the interplay among economic, social, political, and biological constraints. Future forest ecohydrological research should focus on: (1) understanding watershed responses to climate change and variability, (2) understanding watershed responses to losses of native species or additions of non-native species, (3) developing integrated models that capitalize on long-term data, (4) linking ecohydrologic processes across scales, and (5) managing forested watersheds to adapt to climate change. We stress that this new ecohydrology research must also be integrated with socio-economic disciplines.

Warren II, R. J., V. Bahn, T. D. Kramer, Y. Tang, and M. A. Bradford. 2011. Performance and reproduction of an exotic invader across temperate forest gradients. Ecosphere 2(2):art14. doi:10.1890/ES10-00181.1

Abstract
Widespread colonization by invasive species often obscures their underlying niche requirements. A robust inference into habitat requirements demands direct measures of invasive species performance linked with associated environmental conditions. In the context of general ecological theory, we investigated the niche requirements of Microstegium vimineum, an invasive grass in the U.S. that overruns native vegetation in forest understories. We examined M. vimineum’s performance and reproduction as a function of environmental drivers across forested and unforested habitats along a 100-km regional and climatic gradient in the southeastern U.S. from the southern Appalachian Mountains to the Georgia piedmont. We then measured M. vimineum performance and reproduction in response to direct environmental drivers (diffuse light, litter cover, soil moisture, herbaceous cover, soil pH, clay content and temperature) in paired invaded and uninvaded plots. Lastly, we experimentally investigated recruitment in the context of experimental and natural disturbances. We find that all habitats are not equally suitable for M. vimineum—even those within which it occurs—and that the environmental conditions associated with roadsides and waterways are most suitable for M. vimineum persistence and spread. Microstegium vimineum’s soil moisture, light and leaf litter requirements may delineate the boundaries of suitable habitat for the exotic invader. Significant decreases in M. vimineum recruitment, performance and reproduction along these environmental gradients suggest its potential niche limitations. Nevertheless, we also find significant dispersal limits on M. vimineum populations not subject to conspicuous overland water flow. We discuss our findings in the context of spread, impact and management of invasive species.

Warren, R. J. II, V. Bahn, and M. A. Bradford. 2011. Temperature cues phenological synchrony in ant-mediated seed dispersal. Global Change Biology (Online First). doi: 10.1111/j.1365-2486.2010.02386.x.

Abstract
Species-specific climate responses within ecological communities may disrupt the synchrony of co-evolved mutualisms that are based on the shared timing of seasonal events, such as seed dispersal by ants (myrmecochory). The spring phenology of plants and ants coincides with marked changes in temperature, light and moisture. We investigate how these environmental drivers influence both seed release by early and late spring woodland herb species, and initiation of spring foraging by seed-dispersing ants. We pair experimental herbaceous transplants with artificial ant bait stations across north- and south-facing slopes at two contrasting geographic locations. This use of space enables robust identification of plant fruiting and ant foraging cues, and the use of transplants permits us to assess plasticity in plant phenology.We find that warming temperatures act as the primary phenological cue for plant fruiting and ant foraging. Moreover, the plasticity in plant response across locations, despite transplants being from the same source, suggests a high degree of portability in the seed-dispersing mutualism. However, we also find evidence for potential climate-driven facilitative failure that may lead to phenological asynchrony. Specifically, at the location where the early flowering species (Hepatica nobilis) is decreasing in abundance and distribution, we find far fewer seed-dispersing ants foraging during its fruit set than during that of the later flowering Hexastylis arifolia. Notably, the key seed disperser, Aphaenogaster rudis, fails to emerge during early fruit set at this location. At the second location, A. picea forages equally during early and late seed release. These results indicate that climate-driven changes might shift species-specific interactions in a plant–ant mutualism resulting in winners and losers within the myrmecochorous plant guild.

Warren, R. J., D. K. Skelly, O. J. Schmitz, and M. A. Bradford. 2011. Universal ecological patterns in college basketball communities. PLoS ONE, 6(3): e17342.

Abstract
The rank abundance of common and rare species within ecological communities is remarkably consistent from the tropics to the tundra. This invariant patterning provides one of ecology’s most enduring and unified tenets: most species rare and a few very common. Increasingly, attention is focused upon elucidating biological mechanisms that explain these species abundance distributions (SADs), but these evaluations remain controversial. We show that college basketball wins generate SADs just like those observed in ecological communities. Whereas college basketball wins are structured by competitive interactions, the result produces a SAD pattern indistinguishable from random wins. We also show that species abundance data for tropical trees exhibits a significant-digit pattern consistent with data derived from complex structuring forces. These results cast doubt upon the ability of SAD analysis to resolve ecological mechanism, and their patterning may reflect statistical artifact as much as biological processes.

Warren, R. J., II, Bradford, M.A., 2011, Ant colonization and coarse woody debris decomposition in temperate forests. Insectes Sociaux Vol 59:2, Nov. 19, 2011, DOI 10.1007/s00040-011-0208-4

Abstract
Ants are ubiquitous, abundant and have widespread impacts on ecological communities and ecosystem processes. However, ant effects on coarse woody debris decomposition are unexplored. Several ant species colonize coarse woody debris for nesting, and this puts them in contact with fauna and microbes that utilize coarse woody debris as habitat and food, potentially influencing nutrient cycling and, ultimately, forest productivity. We report results from afield experiment employing 138 artificial ant nests (routed pine blocks) across five locations in southeastern US deciduous forests. We examine the correspondence between ant, termite and wood-eating fungi colonization and variation in coarse woody debris decomposition. After 1 year, nests colonized by ants had 5% more mass than those not colonized. Ant colonization corresponded with significantly less termite- and fungal-mediated decomposition of the nests. Without ants, termites removed 11.5% and fungi removed 4% more wood biomass. Ants, termites and woodeating fungi all colonized pine nests where temperatures were highest, and ants also preferred higher soil moisture whereas termites and fungi responded negatively to high soil moisture when temperatures were higher. Ants reduce termite colonies through predation, and may inhibit fungi through the secretion of antimicrobial compounds. Our results indicate that interactions between forest understory ants, termites and fungi may influence the rate of coarse woody debris decomposition—biotic interactions that potentially influence forest structure and function.

Warren, Robert J., II, Bahn, V., and Bradford, M.A., 2011, The interaction between propagule pressure, habitat suitability and density-dependent reproduction in species invasion, Oikos: Synthesizing Ecology, November 2011, http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2011.20174.x/abstract

Abstract
Seedling recruitment limitations create a demographic bottleneck that largely determines the viability and structure of plant populations and communities, and pose a core restriction on the colonization of novel habitat. We use a shadetolerant, invasive grass, Microstegium vimineum, to examine the interplay between seed and establishment limitations – phenomena that together determine recruitment success but usually are investigated individually. We add increasing amounts of seed to microhabitats containing variable levels of leaf litter thickness – with reduced leaf litter simulating disturbance – to investigate whether reduced seed limitation overcomes the establishment limitation posed by litter cover. We do this across gradients in understory light, moisture and temperature, and quantify germination, survival, and then per capita adult biomass and reproduction in order to understand the implications for invasion across the landscape. We find that the combined effects of seed and establishment limitation influence recruitment; however, propagule pressure overwhelms the inhibitory effects of leaf litter thickness. Leaf litter reduces germination by 22–57% and seedling survival by 13–15% from that observed on bare soil. However, density-dependent reproduction compensates as 1–3 plants can produce far more seeds (approx. 525) than are required for persistence. As such, just a few plants may establish in understory forest habitat and subsequently overwhelm establishment barriers with copious propagule production. These results, for a widespread, invasive plant, are consistent with the emerging perspective for native plants that seed and establishment limitation jointly influence recruitment. The ability for an exotic plant species to compensate for low population densities with high per capita seed production, that then overrides establishment limitations, makes its invasive potential daunting. Further work is required to test if this is a common mechanism underlying plant invasions.

Warren, Robert J., Justin P. Wright, Mark A. Bradford. 2011. The Putative Niche Requirements and Landscape Dynamics of Microstegium vimineum: an Invasive Asian Grass. Biological Invasions 13: 471-483

Abstract
The theoretical foundations of population and community ecology stress the importance of identifying crucial niche requirements and life history stages of invasive species and, in doing so, give insight into research and management. We focus on Microstegium vimineum, an invasive grass which is causing marked changes in the structure and function of US forests. We describe M. vimineum’s life history and habitat characteristics, infer its niche requirements and synthesize this information in the context of population dynamics and management. Based on the results synthesized here, M. vimineum’s crucial niche requirements appear to be light (reproductive output), soil moisture (reproductive output, seedling recruitment) and aboveground coverage by leaf-litter and competing species (seedling recruitment and survival). These data suggest a source-sink dynamic might allow M. vimineum to disperse and thrive along sunny, and sometimes wet, edge habitats and, in turn, these populations might act as source populations for adjacent shady forest habitats. By evaluating M. vimineum in the context of its stage-specific requirements, we highlight potential weaknesses in its life history that provide strategies for effective management.

Wei, X., G. Sun, J. M. Vose, K. Otsuki, Z. Zhang, and K. Smetterm. 2011. Forest ecohydrological processes in a changing environment. Ecohydrology, 4: 143-145.

Abstract
The papers in this issue are a selection of the presentations made at the second International Conference on Forests and Water in a Changing Environment. This special issue ‘Forest Ecohydrological Processes in a Changing Environment’ covers the topics regarding the effects of forest, land use and climate changes on ecohydrological processes across forest stand, watershed and regional spatial scales.

Wu, W., J.S. Clark, and J. Vose. 2011. Assimilating multi-source uncertainties of a parsimonious conceptual hydrological model using hierarchical Bayesian modeling. Journal of Hydrology, 394, 436-446.

Abstract
HierarchicalBayesian (HB) modeling allows for multiple sources of uncertainty by factoring complex relationships into conditional distributions that can be used to draw inference and make predictions. We applied an HB model to estimate the parameters and state variables of aparsimonioushydrologicalmodel – GR4J – by coherently assimilating the uncertainties from the model, observations, and parameters at Coweeta Basin in western North Carolina. A state-space model was within the Bayesianhierarchical framework to estimate the daily soil moisture levels and their uncertainties. Results show that the posteriors of the parameters were updated from and relatively insensitive to priors, an indication that they were dominated by the data. The uncertainties of the simulated streamflow increased with streamflow increase. By assimilating soil moisture data, the model could estimate the maximum capacity of soil moisture accounting storage and predict storm events with higher precision compared to not assimilating soil moisture data. This study has shown that hierarchica lBayesianmodel is a useful tool in water resource planning and management by acknowledging stochasticity.

Wurzburger, N., Higgins, B.P. and Hendrick, R. 2011. Ericoid mycorrhizal root fungi and their multi-copper oxidases from a temperate forest shrub. (DOI: 10.1002/ece3.67)

Abstract
Ericoid mycorrhizal fungi (ERM) may specialize in capturing nutrients from theirhost’s litter as a strategy for regulating nutrient cycles in terrestrial ecosystems. Inspite of their potential significance,we knowlittle about the structure ofERMfungalcommunities and the genetic basis of their saprotrophic traits (e.g., genes encodingextracellular enzymes). Rhododendron maximumis amodel ERM understory shrubthat influences the nutrient cycles of montane hardwood forests in the southernAppalachians (North Carolina, USA).We sampled ERMroots of R. maximum fromorganic and mineral soil horizons and identified root fungi by amplifying and sequencinginternal transcribed spacer (ITS) ribosomal DNA (rDNA) collected fromcultures and clones. We observed 71 fungal taxa on ERM roots, including knownsymbionts Rhizoscyphus ericae and Oidiodendron maius, putative symbionts fromthe Helotiales, Chaetothyriales, and Sebacinales, ectomycorrhizal symbionts, andsaprotrophs. Supporting the idea that ERM fungi are adept saprotrophs, richness ofroot-fungi was greater in organic than in mineral soil horizons. To study the geneticdiversity of oxidative enzymes that contribute to decomposition, we amplified andsequenced a portion of genes encoding multicopper oxidases (MCOs) from ERMascomycetes. Most fungi possessed multiple copies of MCO sequences with strongsimilarities to known ferroxidases and laccases. Our findings indicate that R. maximumassociates with a taxonomically and ecologically diverse fungal community.The study of MCO gene diversity and expression may be useful for understandinghow ERM root fungi regulate the cycling of nutrients between the host plant andthe soil environment.

Yamashita, Youhei, Brian D. Kloeppel, Jennifer Knoepp, Gregory L. Zausen and Rudolf Jaffe. 2011. Effects of Watershed History on Dissolved Organic Matter Characteristics in Headwater Streams in Ecosystems 14:1110-1122.

Abstract
Dissolved organic matter (DOM) is recognized as a major component in the global carbon cycle and is an important driver in aquatic ecosystem function. Climate, land use, and forest cover changes all impact stream DOM and alter biogeochemical cycles in terrestrial environments. We determined the temporal variation in DOM quantity and quality in headwater streams at a reference watershed (REF), a watershed clear-cut 30 years ago (CC), and a watershed converted to a white pine plantation 50 years ago (WP) at the US Forest Service, Coweeta Hydrologic Laboratory, in the Nantahala Mountains of western North Carolina, USA. Average stream dissolved organic carbon (DOC) concentrations in CC or WP were 60 and 80% of those in REF, respectively. Stream DOM composition showed that the difference was mainly due to changes in humic-like components in chromophoric DOM. In addition, excitation–emission matrix fluorescence data with parallel factor analysis indicate that although the concentration of protein-like components did not differ significantly among watersheds, their relative abundance showed an enrichment in CC and WP compared to REF. The ratio of humic acid-type to fulvic acid-type components was highest and lowest at REF and WP, respectively. Our data suggest that forest ecosystem disturbance history affects the DOM quantity and quality in headwater streams over decades as a result of changes in watershed soil organic matter characteristics due to differences in organic matter inputs.

Bernot, M. J., D. J. Sobota, R. O. Hall, Jr, P. J. Mulholland, W. K. Dodds, J. R. Webster, J. L. Tank, L. R. Ashkenas, L. W. Cooper, C. N. Dahm, S. V. Gregory, N. B. Grimm, S. K. Hamilton, S. L. Johnson, W. H. McDowell, J. L. Meyer, B. Peterson, G. C. Poole, H. M. Valett, et al. 2010. Inter-regional comparison of land-use effects on stream metabolism. Freshwater Biology, 55: 1874-1890.

Abstract
1. Rates of whole-system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first-order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban-influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona /New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land-use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land-use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land-use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land-use categories showed reduced inter-regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.

Bradford, M.A., B. W. Watts, C. A. Davies. 2010. Thermal adaptation of heterotrophic soil respiration in laboratory microcosms. Global Change Biology, 16: 1576-1588.

Abstract
Respiration of heterotrophic microorganisms decomposing soil organic carbon releases carbon dioxide from soils to the atmosphere. In the short term, soil microbial respiration is strongly dependent on temperature. In the long term, the response of heterotrophic soil respiration to temperature is uncertain. However, following established evolutionary tradeoffs, mass-specific respiration (Rmass) rates of heterotrophic soil microbes should decrease in response to sustained increases in temperature (and vice-versa). Using a laboratory microcosm approach, we tested the potential for the Rmass of the microbial biomass in six different soils to adapt to three, experimentally imposed, thermal regimes (constant 10, 20 or 30 °C). To determine Rmass rates of the heterotrophic soil microbial biomass across the temperature range of the imposed thermal regimes, we periodically assayed soil subsamples using similar approaches to those used in plant, animal and microbial thermal adaptation studies. As would be expected given trade-offs between maximum catalytic rates and the stability of the binding structure of enzymes, after 77 days of incubation Rmass rates across the range of assay temperatures were greatest for the 10 °C experimentally incubated soils and lowest for the 30 1C soils, with the 20 °C incubated soils intermediate. The relative magnitude of the difference in Rmass rates between the different incubation temperature treatments was unaffected by assay temperature, suggesting that maximum activities and not Q10 were the characteristics involved in thermal adaptation. The time taken for changes in Rmass to manifest (77 days) suggests they likely resulted from population or species shifts during the experimental incubations; we discuss alternate mechanistic explanations for those results we observed. A future research priority is to evaluate the role that thermal adaptation plays in regulating heterotrophic respiration rates from field soils in response to changing temperature, whether seasonally or through climate change.

Brookshire, J., S. Gerber, J.R. Webster, J.M. Vose, and W.T. Swank. Direct effects of temperature on forest nitrogen cycling revealed through analysis of long term watershed records. Global Change Biology

Abstract
The microbial conversion of organic nitrogen (N) to plant available forms is a critical determinant of plant growth and carbon sequestration in forests worldwide. In temperate zones, microbial activity is coupled to variations in temperature, yet at the ecosystem level, microbial N mineralization seems to play a minor role in determining patterns of N loss. Rather, N losses often appear to vary with seasonality in hydrology and plant demand, while exports over longer periods are thought to be associated with increasing rates of anthropogenic N deposition. We analyzed long-term (21–32 years) time series of climate and stream and atmospheric chemistry from two temperate deciduous forest watersheds in the southeastern USA to understand the sensitivity of internal forest N cycles to climate variation and atmospheric deposition. We evaluated the time series with a simple analytical model that incorporates key biotic constraints and mechanisms of N limitation and cycling in plant–soil systems. Through maximum likelihood analysis, we derive biologically realistic estimates of N mineralization and its temperature sensitivity (Q10).We find that seasonality and long-term trends in stream nitrate (NO3) concentrations can in large part be explained by the dynamics of internal biological cycling responding to climate rather than external forcing from atmospheric chemistry. In particular, our model analysis suggests that much of the variation in N cycling in these forests results from the response of microbial activity to temperature, causing NO3 losses to peak in the growing season and to accelerate with recent warming. Extrapolation of current trends in temperature and N deposition suggests that the upturn in temperature may increase future N export by greater than threefold more than from increasing deposition, revealing a potential direct effect of anthropogenic warming on terrestrial N cycles.

Bruce, R. C. 2010. Proximate contributions to adult body size in two species of dusky salamanders (Plethodontidae: Desmognathus). Herpetologica, 66(4): 393-402.

Abstract
I used skeletochronological data to evaluate the contributions of propagule size, larval/juvenile growth, and age at first reproduction to differences in adult body size in two species of plethodontid salamanders of the genus Desmognathus. The traits in question were evaluated in populations of the larger D. quadramaculatus and smaller D. monticola in the southern Blue Ridge Mountains of North Carolina, USA. Gompertz and von Bertalanffy functions were fitted to the plots of standard length on skeletochronological age of each complete sample (larvae and/or juveniles, and adults) of earlier data sets; linear functions were fitted to data of immatures (larvae and/or juveniles). In order to examine the relationship of body mass and age, I conducted regressions of body mass on standard length in later samples of both species, calculated estimated body masses of the salamanders in the skeletochronological data sets, and then fitted a modified Gompertz function to each plot of body mass on age. The results showed that age at first reproduction is the principal factor contributing to differences between the species in size at first reproduction and adult size. Larger propagule sizes (i.e., hatching sizes) in D. quadramaculatus versus D. monticola may also be a factor; however, there is no evidence that a difference in larval/juvenile growth rate contributes to the adult size differential. Comparison of two populations of D. monticola suggested that small differences in adult body size result mainly from slight differences in age at first reproduction. Tradeoffs among propagule size, clutch size, growth, and age and size at first reproduction are discussed in the context of selective pressures that may have generated diversification in body size and life history in the genus.

Burt, T. P. and W. T. Swank. 2010. Classics in physical geography revisited: Hursh CR and Brater EF (1941) Separating storm-hydrographs from small drainage-areas into surface-and subsurface-flow. Transactions, American Geophysical Union 22: 863–871. Progress in Physical Geography, 1-8.

Clark, J.S., D. Bell, C. Chu, B. Courbaud, M. Dietze, M. Hersh, J. HilleRisLambers, I. Ibanez, S. L. LaDeau, S. M. McMahon, C.J.E. Metcalf, J. Mohan, E. Moran, L. Pangle, S. Pearson, C. Salk, Z. Shen, D. Valle, and P. Wyckoff. 2010. High dimensional coexistence based on individual variation: a synthesis of evidence. Ecological Monographs, 80:569-608

Abstract
High biodiversity of forests is not predicted by traditional models, and evidence for tradeoffs those models require is limited. High dimensional regulation (e.g., N factors to regulate N species) has long been recognized as a possible alternative explanation, but it has not be been seriously pursued, because only a few limiting resources are evident for trees, and analysis of multiple interactions is challenging. We develop a hierarchical model that allows us to synthesize data from long-term, experimental data sets with processes that control growth, maturation, fecundity, and survival. We allow for uncertainty at all stages and variation among 26,000 individuals and over time, including 268,000 tree years, for dozens of tree species. We estimate population level parameters that apply at the species level and the interactions among latent states, i.e., the demographic rates for each individual, every year. The former show that the traditional tradeoffs used to explain diversity are not present. Demographic rates overlap among species, and they do not show trends consistent with maintenance of diversity by simple mechanisms (negative correlations and limiting similarity). However, estimates of latent states at the level of individuals and years demonstrate that species partition environmental variation. Correlations between responses to variation in time are high for individuals of the same species, but not for individuals of different species. We demonstrate that these relationships are pervasive, providing strong evidence that high dimensional regulation is critical for biodiversity regulation.

Clark, James S. 2010. Individuals and the Variation Needed for High Species Diversity in Forest Trees. Science, 327: 1129-1132.

Abstract
In the past, explanations for high species diversity have been sought at the species level. Theory shows that coexistence requires substantial differences between species, but species-level data rarely provide evidence for such differences. Using data from forests in the southeastern United States, I show here that variation evident at the individual level provides for coexistence of large numbers of competitors. Variation among individuals within populations allows species to differ in their distributions of responses to the environment, despite the fact that the populations to which they belong do not differ, on average. Results are consistent with theory predicting that coexistence depends on competition being stronger within than between species, shown here by analysis of individual-level responses to environmental fluctuation.

Clinton, B. D., J. M. Vose, J. D. Knoepp, K. J. Elliott, B. C. Reynolds, and S. J. Zarnoch. 2010. Can structural and functional characteristics be used to identify riparian zone width in southern Appalachian headwater catchments?. Canadian Journal of Forest Research, 40: 235-353.

Abstract
We characterized structural and functional attributes along hillslope gradients in headwater catchments. We endeavored to identify parameters that described significant transitions along the hillslope. On each of four catchments, we installed eight 50 m transects perpendicular to the stream. Structural attributes included woody and herbaceous vegetation; woody debris and forest floor mass, nitrogen (N) and carbon (C); total soil C and N; litterfall amount and quality by species; and microclimatic conditions. Functional attributes included litter decomposition, soil microarthropods, soil CO2 evolution, soil solution chemistry, and soil extractable N. Forest floor mass, N and C, and soil depth increased with distance from the stream and transitioned between 10 and 20 m. In contrast, litterfall N rate (kilograms of nitrogen per hectare per day), downed woody debris, soil A-horizon C and N, and soil solution NO3 concentration all decreased with distance, and exhibited significant transitions. Certain overstory species were more adundant in the uplands than near the stream. Herbaceous diversity and richness were similar across the hillslope, but species distributions varied in response to hillslope moisture content. Taken together, these results suggest that at 10-20 m from the stream, transitions occur that separate riparian from upland conditions and may provide valuable insight into riparian zone definition.

Clinton, B.D, J.M. Vose, J.D. Knoepp, K.J. Elliott, and B. Reynolds. 2010. Riparian area structure and function in the southern Appalachian headwater streams. Canadian Journal of Forest Research 40(2): 235-253.

Abstract
We characterized structural and functional attributes along hillslope gradients in headwater catchments. We endeavored to identify parameters that described significant transitions along the hillslope. On each of four catchments, we installed eight 50 m transects perpendicular to the stream. Structural attributes included woody and herbaceous vegetation; woody debris and forest floor mass, nitrogen (N) and carbon (C); total soil C and N; litterfall amount and quality by speciesl and microclimate conditions. Functional attributes included litter decomposition, soil microarthropods, soil CO2 evolution, soil solution chemistry, and soil extractable N. Forest floor mass, N and C, and soil depth increased with distance from the stream and transitioned between 10 and 20 m. In contrast, litterfall N rate (kilograms of nitrogen per hectare per day), downed woody debris, soil A-horizon C and N, and soil solution N03 concentration all decreased with distance, and exhibited significant transactions. Certain overstory species were more abundant in the uplands than near the stream. Herbaceous diversity and richness were similar across the hillslope, but species distributions varied in response to hillslope moisture content. Taken together, these results suggest that at 10-20 m from the stream, transitions occur that separate riparian from upland conditions and may provide valuable insight into riparian zone definition.

Clinton, Barton D.; Vose, James M.; Fowler, Dick L. 2010. Flat Branch monitoring project: stream water temperature and sediment responses to forest cutting in the riparian zone. Res. Pap. SRS–51. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 8 p.

Abstract
Stream water protection during timber-harvesting activities is of primary interest to forest managers. In this study, we examine the potential impacts of riparian zone tree cutting on water temperature and total suspended solids. We monitored stream water temperature and total suspended solids before and after timber harvesting along a second-order tributary of the Coleman River in northeastern Georgia, where logging with rubber-tired skidders was conducted in the riparian area along alternating 60-m stream reaches on the east side of the stream. We monitored temperature above the management unit (reference), at a location within the cut area (within cut), and at a third site 150 m below the cut area (below cut). We measured total suspended solids during base flow and storm flow, taking weekly stream water grab samples above the site and above and below each riparian area, for a total of six sampling locations. We found that stream water temperature following harvest increased within the cut area relative to the reference but decreased at the below sample site back to reference conditions. Overall, total suspended solids responses were minimal or nonexistent during base and storm flows within the cut relative to the reference site, and temperature responses were minimal. Unusually warm and dry weather existed for most of the logging period, which may have minimized the potential for runoff, erosion, and sediment; however, low flows may have contributed to the small increases in water temperature. Hence, we observed only marginal effects of riparian zone cutting on water temperature and total suspended solids in this study.

Davis, Andrew K., Cecala, K. (2010) Intraerythrocytic rickettsial inclusions in Ocoee salamanders (Desmognathus ocoee): prevalence, morphology, and comparisons with inclusions of Plethodon cinereus. Parasitol Research, 107:363-367. DOI 10.1007/s00436-010-1869-z

Abstract
Reports of an unusual intraerythrocytic pathogen in amphibian blood have been made for decades; these pathogens appear as membrane-bound vacuoles within erythrocytes. It is now understood that the pathogen is a Rickettsia bacteria, which are obligate intracellular parasites, and most are transmitted by arthropod vectors. In an effort to further understand the host range and characteristics of this pathogen, we examined 20 Ocoee salamanders (Desmognathus ocoee) from a site in southwest North Carolina for the presence of rickettsial inclusions and report the general characteristics of infections. Seven individuals (35%) were infected, and this level of prevalence was consistent with all other members of this genus examined to date. In contrast, infections within the genus Plethodon tend to occur in less than 10% of individuals, based on review of the literature. The difference could be related to the semi-aquatic nature of Desmognathus salamanders versus the completely terrestrial Plethodon. It is also possible that both groups are hosts to different types of rickettsial bacteria, since the inclusions found here only vaguely resembled those found recently in red-backed salamanders (Plethodon cinereus). Inclusions in Ocoee salamanders measured 4 microm in diameter on average, and most cells (88%) only had one inclusion. Of all infected individuals, inclusions occurred in approximately 3% of erythrocytes. Similar to that found in red-backed salamanders, infected hosts were significantly larger than non-infected. Future investigations into the nature of this unusual parasite of amphibians would help to further our understanding of its life cycle and transmission.

Davis, J. M., A. D. Rosemond, S. L. Eggert, W. F. Cross, and J. B. Wallace. 2010. Nutrient enrichment differentially affects body sizes of primary consumers and predators in a detritus-based stream. Limnology and Oceangraphy, 55(6): 2305-2316.

Abstract
We assessed how a 5-yr nutrient enrichment affected the responses of different size classes of primary consumers and predators in a detritus-based headwater stream. We hypothesized that alterations in detritus availability because of enrichment would decrease the abundance and biomass of large-bodied consumers. In contrast, we found that 2 yr of enrichment increased the biomass and abundance of all consumers regardless of body size. Furthermore, during the fourth and fifth year of enrichment, the abundance and biomass of largebodied primary consumers continued to increase, while small-bodied primary consumers returned to pretreatment levels. The size structure of a dominant primary consumer (Pycnopsyche spp.) also shifted during the 5-yr enrichment: its average and maximum individual body size increased in the treatment stream compared with the reference stream. Positive enrichment effects also occurred on small-bodied predators, but not on large-bodied predators. Thus, enrichment increased prey body size, but these positive effects on large prey did not propagate up to higher trophic levels to affect large predators. Because consumer body size can be an important species-specific trait determining population dynamics and ecosystem processes, these observed shifts in consumer size distributions suggest a potentially important pathway for global increases in nutrient enrichment to alter stream structure and function.

Dehring, C. A., C. A. Depken II. 2010. Sharing the Burden of Water Supply Protection. Regulation: 36-40.

Abstract
A sufficient supply of freshwater is critical to human survivability and biodiversity. Much of the recent decline in freshwater biodiversity and overall freshwater ecosystem health is attributable to land use change. Land use practices that influence freshwater include agriculture, forestry, mining, industrialization, and urbanization. While agriculture has historically been viewed as the land use practice most likely to adversely affect water quality, urban development is now seen as the greatest threat to freshwater ecosystems in certain parts of the United States.

Elliott, K. J., J. M. Vose. 2010. The contribution of the Coweeta Hydrologic Laboratory to developing an understanding of long-term (1934-2008) changes in managed and unmanaged forests. Forest Ecology and Management.

Abstract
Long-term records from USDA Forest Service Experimental Forests and Ranges (EF&Rs) are exceptionally valuable scientific resources and common ground for research in natural resource management. Coweeta Hydrologic Laboratory, Southern Appalachian Mountains in western North Carolina, is one of 82 EF&Rs located throughout the United States and Puerto Rico. Since its establishment in 1934, the wealth and breadth of scientific knowledge gained from Coweeta Hydrologic Laboratory research has provided both public and private land managers information on forest land management and has added to the knowledge base of natural resource science. We described the early watershed research at Coweeta and used long-term measurements and inventories (from 1934 to 2008) to: (1) explore the influences of large-scale disturbances and vegetation responses on ecosystem processes and (2) assess the long-term and short-term impacts of an exotic, invasive species on a southern Appalachian deciduous forest. We focused on changes in vegetation patterns influenced by natural and managed disturbances and then described the linkages between long-term vegetation measurements and water yield and quality responses. For natural disturbances, we used a network of over 900 permanent vegetation plots established in reference watersheds and unmanaged areas; first measured in 1934 and a subset re-measured in 1969–1972, 1988–1993, and 2003–2008. For the managed disturbances, clearcuts and species conversion experiments, vegetation was measured in permanent plots within treated watersheds before and after treatment. By the time of the 1934 survey, the forest had only 10 years to recover from logging before chestnut blight (Cryphonectria parasitica) induced mortality of virtually all remaining Castanea dentata trees. With the loss of C. dentata as the dominant species, Acer rubrum and Quercus montana became the dominant species and Liriodendron tulipifera and Tsuga canadensis increased in coves and along riparian corridors. T. canadensis is currently threatened by another invasive species, hemlock woolly adelgid (HWA, Adelges tsugae), with 33% tree mortality between 2003 and 2008. Smaller-scale disturbances, such as drought and windthrow, have created canopy gaps and the disturbance agent, gap size, and species-specific demography (dispersal, survival, growth, and mortality) affected colonization and recruitment. In general, the composition of species recruiting into canopy gapswasa reflection of the vegetation already in place at the time of disturbance, because regeneration occurred primarily through saplings or sprouts. In managed forests, where gaps were much larger (9–59 ha), early successional species recruit and become established and the long-term vegetation patterns are different than in unmanaged forests. The vegetation data provide a description of changes in forest structure and composition through time and space, and they have been used to develop process-based models to scale-up to the catchment level. Long-term climatic, hydrologic, biogeochemical, and vegetation databases coupled with process-based ecohydrology and ecophysiology models are essential to understanding broader- and more complex environmental issues such as climate change, carbon cycling, atmospheric deposition, and water supply and quality.

Elliott, K. J., Vose, J. M. 2010. Short-term effects of prescribed fire on mixed oak forests in the southern Appalachians: vegetation response. Journal of the Torrey Botanical Society, 137(1): 49-66.

Abstract
We examined vegetation responses to prescribed fire on three mixed-oak sites located in the Blue Ridge Physiographic province of the southern Appalachian Mountains: Alarka Laurel Branch (AL), Robin Branch (RB), and Roach Mill Branch (RM). Each of the study sites was within a sub-watershed that drained a first order stream. Our objectives were to: 1) evaluate overstory mortality following prescribed fire treatments; and 2) assess changes in composition, abundance, and diversity of overstory (stems = cm dbh), understory (stems , < cm dbh, = 0.5 m height), and herbaceous layer (woody stems < 0.5 m height and all herbaceous plants) vegetation in mixed-oak ecosystems. Each site included a burned and unburned area (control). Before the prescribed fire treatments were applied, we established permanent plots (10 x 20 m) in the prescribed burn areas (12 plots in AL, 12 plots in RB, and 10 plots in RM) and adjacent unburned areas (5 plots in AL, 6 plots in RB, and 4 plots in RM), for a total of 49 plots. Within the plots, we sampled vegetation before and after the prescribed burns. All of the prescribed fires were low to moderate intensity; i.e., they had moderate flame temperatures and low flame heights. After the prescribed fires, overstory mortality was low for all sites, and there were no significant differences between mortality in burned areas and that in unburned areas. Understory density was lower on the burned than the unburned plots the first (t = -5.26, P < 0.0001) and second (t = -3.85, P = 0.0020) growing seasons after burning. There was either an increase (AL, RB) or no change (RM) in herbaceous layer cover depending on the site and no significant change in species diversity after burning for any site. Thus, we found no negative effects of prescribed fire on herbaceous flora.

Ely, D. T. and J. B. Wallace. 2010. Long-term functional group recovery of lotic macroinvertebrates from logging disturbance. Canadian Journal of Fisheries and Aquatic Sciences, 67: 1126-1134.

Abstract
Clear-cut logging rapidly affects stream macroinvertebrates through substantial alteration of terrestrial-aquatic resource linkages; however, lesser known are the long-term influences of forest succession on benthic macroinvertebrate assemblages, which play key roles in stream ecosystem function. We compared secondary production and standing crops of detritus in two mountain headwater streams within Coweeta Hydrologic Laboratory, North Carolina, USA, as part of a long-term, paired-watershed investigation of macroinvertebrate recovery from whole-carchment logging.

F. Thigpen, T & J. Humphries, W & Maerz, John. (2010). Effectiveness of using artificial shelters to sample arboreal green salamander populations in the Blue Ridge Mountains of Georgia and North Carolina. Herpetological Review. 41. 159-162.

Ford, C. R., E. S. Minor, G. A. Fox. 2010. Long-term effects of fire and fire-return interval on population structure and growth of longleaf pine (Pinus palustris). Canadian Journal of Forest Research, 40:1410-1420.

Abstract
We investigated the effect of fire and fire frequency on stand structure and longleaf pine (Pinus palustris P. Mill.) growth and population demography in an experimental research area in a southwest Florida sandhill community. Data were collected from replicated plots that had prescribed fire-return intervals of 1, 2, 5, or 7 years or were left unburned. Experimental treatment burns have been ongoing since 1976. Plots were sampled to estimate species distribution, stand structure, and longleaf pine density in four developmental stage classes: grass, bolting, small tree, and large tree. Tree-ring growth measurements in combination with burn history were used to evaluate the effects of fire and fire-return interval on basal area increment growth. Fire-return interval impacted stand structure and longleaf pine population structure. Our results suggest that recruitment from the bolting stage to later stages may become adversely affected with very frequent fires (e.g., every 1 or 2 years). Although adult tree productivity was negatively impacted during fire years, tree growth during years between fire events was resilient such that growth did not differ significantly among fire-return intervals. Our study shows that the longleaf pine population as a whole is strongly regulated by fire and fire-return interval plays a key role in structuring this population.

Grossman, Gary D., Robert E. Ratajczak, C. Michael Wagner and J. Todd Petty. 2010. Dynamics and Regulation of the southern brook trout (Salvelinus fontinalis) population in an Appalachian stream. Freshwater Biology 55:1494-1508.

Abstract
1. We used information theoretic statistics [Akaike’s Information Criterion (AIC)] and regression analysis in a multiple hypothesis testing approach to assess the processes capable of explaining long-term demographic variation in a lightly exploited brook trout population in Ball Creek, NC. We sampled a 100-m-long second-order site during both spring and autumn 1991–2004, using three-pass electrofishing. 2. Principle component analysis indicated that the site had lower average velocity, greater amounts of depositional substrata and lower amount of erosional substrata during the 1999–2002 drought than in non-drought years. In addition, drought years had lower flows, and lower variation in flows, than non-drought years. 3. Both young-of-the-year (YOY) and adult densities varied by an order of magnitude during the study. AIC analysis conducted on regressions of per capita rate of increase versus various population and habitat parameters for the population, adults and YOY, for both spring and autumn data sets, indicated that simple density dependence almost always was the only interpretable model with Akaike weights (wi) ranging from 0.262 to 0.836. 4. Growth analyses yielded more variable results, with simple density dependence being the only interpretable model for both adult spring data (wi = 0.999) and YOY autumn data (wi = 0.905), and positive density dependence (wi = 0.636) and simple density independence (wi = 0.241) representing interpretable models for spring YOY data. 5. We detected a significant stock–recruitment relationship between both spring and autumn densities of adults in year t and autumn YOY density in year t + 1. Finally, spring YOY density was positively correlated with both autumn YOY density and spring mean YOY standard length (SL), suggesting that processes affecting recruitment show residual effects at least in the first year of life. This population appears to be regulated primarily by density-dependent processes, although high flows also negatively affected mean SLs of YOY.

Hagen, Elizabeth M. Matthew E. McTammany, Jackson R. Webster, Ernest F. Benfield. 2010. Shifts in allochthonous input and autochthonous production in streams along an agricultural land-use gradient. Hydrobiologia. 655(1):61-77.

Abstract
Relative contributions of allochthonous inputs and autochthonous production vary depending on terrestrial land use and biome. Terrestrially derived organic matter and in-stream primary production were measured in 12 headwater streams along an agricultural land-use gradient. Streams were examined to see how carbon (C) supply shifts from forested streams receiving primarily terrestrially derived C to agricultural streams, which may rely primarily on C derived from algal productivity. We measured allochthonous input, chlorophyll a concentration, and periphyton biomass in each stream, and whole-stream metabolism in six streams. Our results suggest a threshold between moderate- and heavy-agriculture land uses in which terrestrially derived C is replaced by in-stream algal productivity as the primary C source for aquatic consumers. A shift from allochthonous to autochthonous production was not evident in all heavy-agriculture streams, and only occurred in heavy-agriculture streams not impacted by livestock grazing. We then compared our findings to rates of allochthonous input and GPP in streams with minimal human influences in multiple biomes to assess how land-use practices influence C sources to stream ecosystems. The proportion of C derived from allochthonous versus autochthonous sources to heavyagriculture streams was most similar to grassland and desert streams, while C sources to forested, light-, and moderate-agriculture streams were more similar to deciduous and montane coniferous forest streams. We show that C source to streams is dependent on land use, terrestrial biome, and degradation of in-stream conditions. Further, we suggest that within a biome there seems to be a compensation such that total C input is nearly equal whether it is from allochthonous or autochthonous sources.

Helton, A.M., G.C. Poole, J.L. Meyer, W.L. Wollheim, B.J. Peterson, P.J. Mulholland, E.S. B ernhardt, J.A. Stanford, C. Arango, L.R. Ashkenas, L.W. Cooper, W.K. Dodds, S.V. Gregory, R.O. Hall, S.K. Hamilton, S.L. Johnson, W.H. McDowell, J.D. Potter, J.L. Tank, S.M. Thomas, H.M. Valett, J.R. Webster, and L. Zeglin. 2010. Thinking outside the channel: Nitrogen cycling in networked river ecosystems. Frontiers in Ecology and the Environment 9(4):229-238.

Abstract
Agricultural and urban development alters nitrogen and other biogeochemical cycles in rivers worldwide. Because such biogeochemical processes cannot be measured empirically across whole river networks, simula- tion models are critical tools for understanding river-network biogeochemistry. However, limitations inherent in current models restrict our ability to simulate biogeochemical dynamics among diverse river networks. We illustrate these limitations using a river-network model to scale up in situ measures of nitrogen cycling in eight catchments spanning various geophysical and land-use conditions. Our model results provide evidence that catchment characteristics typically excluded from models may control river-network biogeochemistry. Based on our findings, we identify important components of a revised strategy for simulating biogeochemical dynamics in river networks, including approaches to modeling terrestrial–aquatic linkages, hydrologic exchanges between the channel, floodplain/riparian complex, and subsurface waters, and interactions between coupled biogeochemical cycles.

Jackson, C. R. and C. M. Pringle. Ecological Benefits of Reduced Hydrologic Connectivity in Intensively Developed Landscapes. BioScience, 60(1): 37-46

Abstract
A broad perspective on hydrologic connectivity is necessary when managing stream ecosystems and establishing conservation priorities. Hydrologic connectivity refers to the water-mediated transport of matter, energy, or organisms within or between elements of the hydrologic cycle. The potential negative consequences of enhancing hydrologic connectivity warrant careful consideration in human-modified landscapes that are increasingly characterized by hydrologic alteration, exotic species, high levels of nutrients and toxins, and disturbed sediment regimes. While connectivity is integral to the structure and function of aquatic ecosystems, it can also promote the distribution of undesirable components. Here we provide examples illustrating how reduced hydrologic connectivity can provide greater ecological benefits than enhanced connectivity does in highly developed, human-modified ecosystems; for example, in urban landscapes, “restoration” efforts can sometimes create population sinks for endangered biota.We conclude by emphasizing the importance of adaptivemanagement and balancing trade-offs associated with further alterations of hydrologic connectivity in human-modified landscapes.

Kuhman, T. R., S. M. Pearson and M. G. Turner. 2010. Effects of land-use history and the contemporary landscape on non-native plant invasion at local and regional scales in the forest-dominated southern Appalachians. Landscape Ecology. 25:1433–1445.

Abstract
The microbial conversion of organic nitrogen (N) to plant available forms is a critical determinant of plant growth and carbon sequestration in forests worldwide. In temperate zones, microbial activity is coupled to variations in temperature, yet at the ecosystem level, microbial N mineralization seems to play a minor role in determining patterns of N loss. Rather, N losses often appear to vary with seasonality in hydrology and plant demand, while exports over longer periods are thought to be associated with increasing rates of anthropogenic N deposition. We analyzed long-term (21–32 years) time series of climate and stream and atmospheric chemistry from two temperate deciduous forest watersheds in the southeastern USA to understand the sensitivity of internal forest N cycles to climate variation and atmospheric deposition. We evaluated the time series with a simple analytical model that incorporates key biotic constraints and mechanisms of N limitation and cycling in plant–soil systems. Through maximum likelihood analysis, we derive biologically realistic estimates of N mineralization and its temperature sensitivity (Q10).We find that seasonality and long-term trends in stream nitrate (NO3) concentrations can in large part be explained by the dynamics of internal biological cycling responding to climate rather than external forcing from atmospheric chemistry. In particular, our model analysis suggests that much of the variation in N cycling in these forests results from the response of microbial activity to temperature, causing NO3 losses to peak in the growing season and to accelerate with recent warming. Extrapolation of current trends in temperature and N deposition suggests that the upturn in temperature may increase future N export by greater than threefold more than from increasing deposition, revealing a potential direct effect of anthropogenic warming on terrestrial N cycles.

Laliberté, E., J. Wells, F. DeClerck, D. Metcalfe, C. Catterall, C. Queiroz, I. Aubin, S. Bonser, Y. Ding, J. M. Fraterrigo, J. Morgan, P. Vesk, and M. Mayfield. 2010. Land use intensification reduces response diversity in plant communities. Ecology Letters 13:76-86.

Abstract
Ecosystem resilience depends on functional redundancy (the number of species contributing similarly to an ecosystem function) and response diversity (how functionally similar species respond differently to disturbance). Here, we explore how land-use change impacts these attributes in plant communities, using data from 18 land-use intensity gradients that represent five biomes and > 2800 species. We identify functional groups using multivariate analysis of plant traits which influence ecosystem processes. Functional redundancy is calculated as the species richness within each group, and response diversity as the multivariate within-group dispersion in response trait space, using traits that influence responses to disturbances. Meta-analysis across all datasets showed that land-use intensification significantly reduced both functional redundancy and response diversity, although specific relationships varied considerably among the different land-use gradients. These results indicate that intensified management of ecosystems for resource extraction can increase their vulnerability to future disturbances.

Leigh, D.S., 2010. Morphology and channel evolution of small streams in the southern Blue Ridge Mountains of western North Carolina. Southeastern Geographer. 50:397-421.

Luo, Y., S. Niu, J. Melillo, C. Beier, J.S. Clark, A. Classen, E. Davidson, J. S. Dukes, D. Evans, C. Field, C. I. Czimczik, M. Keller, L. Kueppers, R. Norby, S. L. Pelini, E. Pendall, E. Rastetter, J. Six, M. Smith, M. Tjoelker, M. Torn. 2010. Coordinated approaches to quantify Long-Term Ecosystem dynamics in response to global change. Global Change Biology, in press.

Abstract
Many serious ecosystem consequences of climate change will take decades or even centuries to emerge. Long-term ecological responses to global change are strongly regulated by slow processes, such as changes in species composition, carbon dynamics in soil and by long-lived plants, and accumulation of nutrient capitals. Understanding and predicting these processes require experiments on decadal time scales. But decadal experiments by themselves may not be adequate becausemany of the slowprocesses have characteristic time scalesmuch longer than experiments can bemaintained. This article promotes a coordinated approach that combines long-term, large-scale global change experiments with process studies andmodeling. Long-term global change manipulative experiments, especially in high-priority ecosystems such as tropical forests and high-latitude regions, are essential to maximize information gain concerning future states of the earth system. The long-term experiments should be conducted in tandem with complementary process studies, such as those using model ecosystems, species replacements, laboratory incubations, isotope tracers, and greenhouse facilities. Models are essential to assimilate data from long-term experiments and process studies togetherwith information from long-term observations, surveys, and space-for-time studies along environmental and biological gradients. Future research programs with coordinated long-term experiments, process studies, and modeling have the potential to be the most effective strategy to gain the best information on long-term ecosystem dynamics in response to global change.

Milanovich, J. R, W. E. Peterman, N. P. Nibbelink, and J. C. Maerz. 2010. Projected loss of a salamander diversity hotspot as a consequence of projected global climate change. PLoS One, 5 (8): 1-10.

Abstract
Background: Significant shifts in climate are considered a threat to plants and animals with significant physiological limitations and limited dispersal abilities. The southern Appalachian Mountains are a global hotspot for plethodontid salamander diversity. Plethodontids are lungless ectotherms, so their ecology is strongly governed by temperature and precipitation. Many plethodontid species in southern Appalachia exist in high elevation habitats that may be at or near their thermal maxima, and may also have limited dispersal abilities across warmer valley bottoms. Methodology/Principal Findings: We used a maximum-entropy approach (program Maxent) to model the suitable climatic habitat of 41 plethodontid salamander species inhabiting the Appalachian Highlands region (33 individual species and eight species included within two species complexes). We evaluated the relative change in suitable climatic habitat for these species in the Appalachian Highlands from the current climate to the years 2020, 2050, and 2080, using both the HADCM3 and the CGCM3 models, each under low and high CO2 scenarios, and using two-model thresholds levels (relative suitability thresholds for determining suitable/unsuitable range), for a total of 8 scenarios per species. Conclusion/Significance: While models differed slightly, every scenario projected significant declines in suitable habitat within the Appalachian Highlands as early as 2020. Species with more southern ranges and with smaller ranges had larger projected habitat loss. Despite significant differences in projected precipitation changes to the region, projections did not differ significantly between global circulation models. CO2 emissions scenario and model threshold had small effects on projected habitat loss by 2020, but did not affect longer-term projections. Results of this study indicate that choice of model threshold and CO2 emissions scenario affect short-term projected shifts in climatic distributions of species; however, these factors and choice of global circulation model have relatively small affects on what is significant projected loss of habitat for many salamander species that currently occupy the Appalachian Highlands.

Mulholland, P.J., Webster, J.R. 2010. Nutrient dynamics in streams and the role of J-NABS. J. N. Am. Benthol. Soc., 29(1):100–117

Abstract
Nutrient dynamics in streams has been an important topic of research since the 1960s. Here we review this topic and the significant role played by J-NABS in its development. We limit this review almost exclusively to studies of N and P because these elements have been shown to limit productivity in streams. We use the expression nutrient dynamics for studies that included some measures of biological processes occurring within streams. Prior to the 1970s, instream biological processes were little studied, but through 1985 conceptual advances were made, and 4 types of studies made important contributions to our understanding of instream processes: 1) evidence of increased plant production and decomposition in response to nutrient addition, 2) studies showing a downstream decrease in nutrient concentrations, 3) studies using radioisotopes, and 4) budget studies. Beginning with the first paper printed in its first issue, J-NABS has been the outlet for key papers advancing our understanding of rates and controls of nutrient dynamics in streams. In the first few years, an important review and a conceptual model for conducting experiments to study nutrient dynamics in streams were published in J-NABS. In the 1990s, J-NABS published a number of papers on nutrient recycling within algal communities, the role of the hyporheic zone, the role of spawning fish, and the coupling of data from field 15N additions and a N-cycling model to provide a synoptic view of N dynamics in streams. Since 2000, J-NABS has published influential studies on nutrient criteria for streams, rates of and controls on nitrification and denitrification, uptake of stream nutrients by riparian vegetation, and nutrient dynamics in urban streams. Nutrient dynamics will certainly continue to be an important topic in J-NABS. Topics needing further study include techniques for studying nutrient dynamics, nutrient dynamics in larger streams and rivers, the ultimate fate of nutrients taken up by plants and microbes in streams, ecological stoichiometry, the effects of climate change, and the role of streams and rivers in nutrient transformation and retention at the landscape scale.

Narayanaraj, G., P. V. Bolstad, K. J. Elliott, J. M. Vose. 2010. Terrain and Landform Influence on Tsuga canadensis (L.) Carrie`re (Eastern Hemlock) Distribution in the Southern Appalachian Mountains. Castenea. 75(1):1-18.

Abstract
We examined the relationships between hemlock distribution and abundance and terrain attributes for the Coweeta Basin in the southern Appalachian Mountains. Field measurements were combined with GIS mapping methods to develop predictive models of abundance and distribution of Tsuga canadensis (L.) Carrie`re (eastern hemlock) and evaluate the co-occurrence of Rhododendron maximum L. (rosebay) and Kalmia latifolia L. (mountain laurel). Terrain variables were derived from USGS DEM 30-meter digital maps. Elevation, slope, aspect, terrain shape index, landform, and distance from stream were calculated from field measurements and the digital data. Terrain attributes such as elevation (r2 = 0.97, p < 0.0001), distance to stream (r2 = 0.94, p < 0.0001), and terrain shape index (r2 = 0.61, p = 0.0015) were good predictors of T. canadensis abundance. Terrain shape index explained 56% of the variation in R. maximum percent aerial cover (r2 = 0.56, p = 0.005). In the Coweeta Basin, T. canadensis was distributed as few, large trees mostly concentrated in near-stream locations, and it was closely associated with R. maximum. Tsuga canadensis mortality due to Adelges tsugae Annand (hemlock wooly adelgid) will result in a minor decrease in basin-wide basal area, but will substantially reduce near-stream basal area, and will also remove the largest trees in nearstream environments. In similar landscapes across the southern Appalachians, where T. canadensis co-occurs with R. maximum, riparian shading will likely remain unchanged.

Palmer, M. A., E. S. Bernhardt, W. H. Schlesinger, K. N. Eshleman, E. Foufoula-Georgiou, M. S. Hendryx, A. D. Lemly, G. E. Likens, O. L. Loucks, M. E. Power, P. S. White, and P. R. Wilcock. 2010. Mountaintop mining consequences. Science, 327: 148-149.

Price, K. Jackson, C.R. Parker, A.J. 2010. Variation of surficial soil hydraulic properties across land uses in the southern Blue Ridge Mountains, North Carolina, USA. Journal of Hydrology, 383: 256-268.

Abstract
A full understanding of hydrologic response to human impact requires assessment of land-use impacts on key soil physical properties such as saturated hydraulic conductivity, bulk density, and moisture retention. Such properties have been shown to affect watershed hydrology by influencing pathways and transmission rates of precipitation to stream networks. Human land use has been shown to influence these soil physical properties as a result of erosion, compaction, and pore structure evolution. Our objective was to characterize soil physical properties under three land-use classes (forest, pasture, and managed lawn) in the southern Blue Ridge Mountains of southwestern North Carolina. A total of 90 points were sampled (30 in each land-use class) throughout a 983 km2 study area. Saprolitic and alluvial soils were emphasized, and sites were selected that showed consistent land-use history over a period of at least 30 years. Particle size distribution, in situ saturated hydraulic conductivity (measured using an Amoozemeter compact constant head permeameter), bulk density, and volumetric moisture content at field capacity were measured at each point. Forest soils demonstrated markedly lower bulk densities and higher infiltration rates, and water holding capacities, than lawn and pasture soils. No soil property significantly differed between pasture and lawn. Mean values for each property were as follows (forest = F, lawn = L, pasture = P): saturated hydraulic conductivity (mm h1) – F = 63, L = 7, P = 8; bulk density (g cm3) – F = 0.8, L = 1.2, P = 1.2; volumetric moisture content (%) – F = 72%, L = 42%, P = 39%. Particle size distributions did not significantly differ among land-use classes or parent materials, and the differences between the hydraulic properties of forest vs. nonforest soils were attributed to compaction associated with land management practices. The magnitudes of differences between forest and nonforest infiltration rates suggest that widespread conversion of forest to other land uses in this region will be accompanied by decreased infiltration and increased overland flow, potentially significantly altering water budgets and leading to reduced baseflows and impaired water quality.

Romito, A. M., S. L. Eggert, J. M. Diez, and J. B. Wallace. 2010. Effects of seasonality and resource limitation on organic matter turnover by Chironomidae (Diptera) in southern Appalachian headwater streams. Limnology and Oceanography, 55(3): 1083-1092.

Abstract
Despite their high abundance, secondary production, and known reliance on detrital material, the role of chironomids (Diptera) in fine particulate organic matter (FPOM) dynamics has not been well quantified. We conducted field trials using fluorescent pigment markers to estimate seasonal rates of consumption, annual secondary production, assimilation efficiency (AE), and FPOM turnover for non-Tanypodinae chironomids in two similar, southern Appalachian, headwater streams. An ecosystem-level experimental manipulation of detrital inputs in one study stream allowed for a unique assessment of turnover in reference, resource-limited, and resource-recovery systems. Seasonality had a significant effect on larval gut-passage time (GPT), with faster GPT at higher temperatures. Mean GPT ranged from 39 min (summer) to 67 min (winter). Mean annual FPOM turnover was reduced in the resource-limited stream (5.5 kg ash-free dry weight per year; 12% of mean annual FPOM export) compared to the reference stream (46 kg yr21; 74% of mean export). Following 4 yr of resource recovery, FPOM turnover increased to 24 kg ash-free dry wt yr21 (16% of export) but remained lower than levels measured in the reference stream (53 kg ash-free dry wt yr21; 20% of export). Chironomid contribution to FPOM turnover was much higher in low vs. high discharge conditions (74% in low discharge vs. 20% in high discharge). Assimilation efficiency was estimated to be low in all systems (1.7–2.5%). Chironomids turned over a large portion of FPOM available to them, suggesting that turnover by the entire collector community in forested headwater systems may be much higher than expected.

Stodola, K. W., D. A. Buehler, D. H. Kim, K. E. Franzreb, and E. T. Linder. 2010. Biotic and abiotic factors governing nestling-period length in the ovenbird (Seiurus aurocapilla). The Auk, 127(1): 204-211.

Abstract
In many songbirds, the nesting period for a breeding attempt is extremely short, often lasting only a few weeks. Breeding adults can shorten this period by decreasing the number of eggs laid or reducing the length of the nestling period. Nestling-period length has received little attention in the literature but could have profound effects on annual fecundity, because each day represents a risk of nest depredation. Consequently, we were interested in assessing the biotic and abiotic factors that govern the nestling period in the Ovenbird (Seiurus aurocapilla). We provide evidence that food availability, more than predation pressure and climatic factors, influences nestling-period length, with increases in food availability decreasing the nestling period. We suggest that the nestling period is dictated by physiological constraints, which may be influenced by food availability and, thus, the ability to provision young. However, the greatest variation in nestling period was individual variation among breeding pairs. Thus, we believe that large-scale variation in ecological and environmental factors may determine the physiological constraints of the nestling period but parental behavior and quality within this framework dictate the actual length of the nestling period.

Stodola, K. W., E. T. Linder, D. A. Buehler, K. E. Franzreb, D. H. Kim, and R. J. Cooper. 2010. Relative influence of male and female care in determining nestling mass in a migratory songbird. Journal of Avian Biology, 41: 515-522.

Abstract
Biparental care is common in birds, with the allocation of effort being highly variable between the sexes. In most songbird species, the female typically provides the most care early in the breeding cycle with both parents providing care when provisioning young. Food provisioning should be directly related to offspring quality; however, the relative influence each parent has on offspring quality has rarely been assessed at the nest level. Consequently, we were interested in assessing the relative influence male and female provisioning has on one measurement of offspring quality, nestling mass, in the blackthroated blue warbler Dendroica caerulescens. Over a six year period, 2003-2008, we collected information on average nestling mass per brood on day 6 of the nestling cycle and parental provisioning rates on day 7 of the nestling cycle from 182 first brood nests on three different study plots. We found that average nestling mass was directly related to male provisioning rate, while it was not related to female provisioning rate. On the other hand, estimated biomass provisioned had little influence on average nestling mass, calling into question its utility in assessing parental quality. Finally, there was some indication that parental influence on average nestling mass was dependent on the other parent’s provisioning rate, suggesting that parents work in concert to influence nestling quality.

Strickland, M. S., J. L. Devore, J. C. Maerz, M. A. Bradford. 2010. Grass invasion of a hardwood forest is associated with declines in belowground carbon pools. Global Change Biology, 16: 1338-1350

Abstract
Invasive plant species affect a range of ecosystem processes but their impact on belowground carbon (C) pools is relatively unexplored. This is particularly true for grass invasions of forested ecosystems. Such invasions may alter both the quantity and quality of forest floor inputs. Dependent on both, two theories, ‘priming’ and ‘preferential substrate utilization’, suggest these changes may decrease, increase, or leave unchanged native plant-derived soil C. Decreases are expected under ‘priming’ theory due to increased soil microbial activity. Under ‘preferential substrate utilization’, either an increase or no change is expected because the invasive plant’s inputs are used by the microbial community instead of soil C. Here, we examine how Microstegium vimineum affects belowground C-cycling in a southeastern US forest. Following predictions of priming theory, M. vimineum’s presence is associated with decreases in native-derived, C pools. For example, in September 2006 M. vimineum is associated with 24%, 34%, 36%, and 72% declines in total organic, particulate organic matter, mineralizable (a measure of microbially-available C), and microbial biomass C, respectively. Soil C derived from M. vimineum does not compensate for these decreases, meaning that the sum of native- plus invasive-derived C pools is smaller than native-derived pools in uninvaded plots. Supporting our inferences that C-cycling accelerates under invasion, the microbial community is more active per unit biomass: added 13C-glucose is respired more rapidly in invaded plots. Our work suggests that this invader may accelerate C-cycling in forest soils and deplete C stocks. The paucity of studies investigating impacts of grass invasion on C-cycling in forests highlights the need to study further M. vimineum and other invasive grasses to assess their impacts on C sink strength and forest fertility.

Strickland, M.S., Callaham, M.A., Jr., Davies, C.A., Lauber, C.L., Ramirez, K., Richter, D.D., Jr., Fierer, N., Bradford, M.A., 2010. Rates of in situ carbon mineralization in relation to land-use, microbial community and edaphic characteristics. Soil Biology & Biochemistry v. 42:2, Feb. 2010, p. 260-269

Suberkropp, K., V. Gulis, A. D. Rosemond, J. P. Benstead. 2010. Ecosystem and physiological scales of microbial responses to nutrients in a detritus-based stream: Results of a 5-year continuous enrichment. Limnology and Oceanography, 55(1): 149-160

Abstract
Our study examined the response of leaf detritus–associated microorganisms (both bacteria and fungi) to a 5-yr continuous nutrient enrichment of a forested headwater stream. Leaf litter dominates detritus inputs to such streams and, on a system-wide scale, serves as the key substrate for microbial colonization. We determined physiological responses as microbial biomass and activity expressed per unit mass of leaves and system-level responses by quantifying leaf litter standing crop monthly and expressing responses per unit area of streambed. Physiological (mass-specific) trends differed from system-level (area-specific) trends. Physiological responses to enrichment were generally positive. With the exception of bacterial biomass, nutrients increased all metrics expressed per unit mass leaf litter in the treatment stream relative to the reference (fungal biomass and production, bacterial production, microbial respiration). This positive physiological response to nutrient enrichment was associated with lower leaf litter standing crop in the treatment stream, resulting in less substrate for microbial colonization. Consequently, during most years on a system-level scale, only fungal production and microbial respiration were positively affected by nutrients, whereas fungal biomass was negatively affected. Thus, from a whole-stream perspective, nutrients led to a lower quantity of leaf detritus with greater variation, resulting in net reductions of associated fungal biomass and greater intra-annual variability in both fungal biomass and respiration. Our results demonstrate profound effects of nutrients on heterotrophic pathways that mediate detritus processing in stream ecosystems. Similar effects on heterotrophic microbes and detrital resources may be a widespread consequence of anthropogenic nutrient enrichment.

Vieilledent, G., B. Courbaud, G. Kunstler, J.-F. Dhote, and J.S. Clark. 2010. Individual variability in tree allometry determines light resource allocation in forest ecosystems: a hierarchical Bayesian approach. Oecolgia, in press.

Abstract
Tree species differences in crown size and shape are often highlighted as key characteristics determining light interception strategies and successional dynamics. The phenotypic plasticity of species in response to light and space availability suggests that intraspecific variability can have potential consequences on light interception and community dynamics. Species crown size varies depending on site characteristics and other factors at the individual level which differ from competition for light and space. These factors, such as individual genetic characteristics, past disturbances or environmental micro-site effects, combine with competition- related phenotypic plasticity to determine the individual variability in crown size. Site and individual variability are typically ignored when considering crown size and light interception by trees, and residual variability is relegated to a residual error term, which is then ignored when studying ecological processes. In the present study, we structured and quantified variability at the species, site, and individual levels for three frequently used tree allometric relations using fixed and random effects in a hierarchical Bayesian framework.Wefocused on two species: Abies alba (silver fir) and Picea abies (Norway spruce) in nine forest stands of the western Alps.Wedemonstrated that species had different allometric relations from site to site and that individual variability accounted for a large part of the variation in allometric relations. Using a spatially explicit radiation transmission model on real stands, we showed that individual variability in tree allometry had a substantial impact on light resource allocation in the forest. Individual variability in tree allometry modulates species’ light-intercepting ability. It generates heterogeneous light conditions under the canopy, with high light micro-habitats that may promote the regeneration of light-demanding species and slow down successional dynamics.

Warren, R. J. and M. A. Bradford. 2010. The shape of things to come: woodland herb niche contraction begins during recruitment in mesic forest microhabitat. Proceedings of the Royal Society B, doi:10.1098/rspb.2010.1886.

Abstract
Natural abundance is shaped by the abiotic requirements and biotic interactions that shape a species’ niche, yet these influences are rarely decoupled. Moreover, most plant mortality occurs during early life stages, making seed recruitment critical in structuring plant populations. We find that natural abundance of two woodland herbs, Hexastylis arifolia and Hepatica nobilis, peaks at intermediate resource levels, a pattern probably formed by concurrent abiotic and biotic interactions. To determine how this abundance patterning reflects intrinsic physiological optima and extrinsic biotic interactions, we translocate adults and seeds to novel locations across experimentally extended abiotic gradients. These experiments indicate that the plant distributions probably reflect biotic interactions as much as physiological requirements, and that adult abundance provides a poor indication of the underlying niche requirements. The positive response exhibited by adult transplants in the wettest conditions is offset by increased fungal attack on buried seeds consistent with peak natural abundance where soil moisture is intermediate. This contraction of niche space is best described by Connell’s model—species are limited by physiological tolerances where resources are low and biotic interactions where resources are high.

Warren, R. J. II, E. Mordecai. 2010. Soil moisture mediated interaction between Polygonatum biflorum and leaf spot disease. Plant Ecology, 209: 1-9.

Abstract
Fungal pathogens can regulate the abundance and distribution of natural plant populations by inhibiting the growth, survival, and reproduction of their hosts. The abiotic environment is a crucial component in host–pathogen interactions in natural plant populations as favorable conditions drive pathogen development, reproduction, and persistence. Foliar plant pathogens, such as fungal lesions referred to generically as ‘‘leaf spot disease,’’ are particularly responsive to increased moisture levels, but the manner in which the abiotic environment drives disease dynamics, and how these diseases regulate natural plant populations, is not fully understood. We investigate (1) the impact of ambient soil moisture and diffuse light on the prevalence of a leaf spot pathogen (Phyllosticta sp.) in a natural population of Polygonatum biflorum, an understory herb native to deciduous forest understories in the eastern US, and (2) the effects of the fungal pathogen on the survival, growth, and abundance of the plants. We tracked six P. biflorum populations and disease incidence, as well as soil moisture and diffuse light, between 2003 and 2005 in the understory deciduous forest of the southern Appalachian Mountains, North Carolina, USA. Results show that both the occurrence of P. biflorum and the prevalence of P. biflorum leaf spot disease are highest where soil moisture is intermediate and diffuse light is lowest. Disease occurrence depends upon plant presence, but it also adversely impacts plant survival, abundance, and growth. These results suggest that leaf spot disease is likely to impact population dynamics, which in turn vary as a function of environmental drivers.

Warren, R.J, and M.A. Bradford. 2010. Seasonal climate trends, the North Atlantic Oscillation and salamander abundance in the southern Appalachian mountain region. Journal of Applied Meteorology and Climatology. 49:1597-1603.

Abstract
The North Atlantic Oscillation (NAO) is a large-scale climate teleconnection that coincides with worldwide changes in weather. Its impacts have been documented at large-scales, particularly in Europe, but not as much at regional scales. Furthermore, despite documented impacts on ecological dynamics in Europe, the NAO’s influence on North American biota has been somewhat overlooked. This paper examines long-term temperature and precipitation trends in the southern Appalachian Mountain region – a region well known for its biotic diversity, particularly in salamander species – and examines the connections between these trends and NAO cycles. In order to connect the NAO phase shifts with southern Appalachian ecology, trends in stream salamander abundance are also examined as a function of the NAO index. The results reported here indicate no substantial long-term warming or precipitation trends in the southern Appalachians, and a strong relationship between cool season (November-April) temperature and precipitation and the NAO. More importantly, trends in stream salamander abundance are best explained by variation in the NAO as salamanders are most plentiful during the warmer, wetter phases.

Zehnder, C. B., K. W. Stodola, R. J. Cooper, and M. D. Hunter. 2010. Spatial heterogeneity in the relative impacts of foliar quality and predation pressure on red oak, Quercus rubra, arthropod communities. Oecologia, 164: 1017-1027.

Abstract
Predation pressure and resource availability often interact in structuring herbivore communities, with their relative influence varying in space and time. The operation of multiple ecological pressures and guild-specific herbivore responses may combine to override simple predictions of how the roles of plant quality and predation pressure vary in space. For 2 years at the Coweeta LTER in the Southern Appalachian Mountains, we conducted a bird exclosure experiment on red oak (Quercus rubra) saplings to investigate the effects of bird predation on red oak arthropod communities. We established bird exclosures at six sites along an elevational gradient and estimated variation in foliar nitrogen and bird predation pressure along this gradient. Foliar nitrogen concentrations increased with elevation while our index of bird predation pressure was variable across sites. Greater arthropod densities were detected inside exclosures; however, this result was mainly driven by the response of phloem feeders which were much more prevalent inside exclosures than on control trees. There was little evidence for an effect of bird predation on the other arthropod guilds. Consequently, there was no evidence of a trophic cascade either in terms of leaf damage or tree growth. Finally, we found more variation in arthropod density among trees within sites than variation in arthropod density among sites, indicating the importance of micro-site variation in structuring arthropod communities.

Albright, T. P., D. P. Anderson. N. S. Keuler. S. M. Pearson. M. G. Turner. 2009. The spatial legacy of introduction: Celastrus orbiculatus in the southern Appalachians, USA. Journal of Applied Ecology, 46:1229-1238

Abstract
1. A variety of abiotic, biotic, human and historic variables related to environmental suitability and propagule pressure determine the distribution of invasive plants in a landscape. Understanding the role of these variables for invasive species is challenging because environmental variables are often correlated, many invaders have broad ecological niches, and invasive distributions are often highly dynamic. 2. We examined the role of environmental variables at multiple spatial scales on the distribution of an invasive vine Celastrus orbiculatus (Celastraceae) in the southern Appalachians, USA. Using existing and newly collected occurrence data, we constructed spatial generalized linear mixed models of C. orbiculatus occurrence in the whole region as well as the areas nearest (established zone) and farthest (pioneer zone) fromthe purported introduction locus. 3. For the entire study region, distance from the introduction locus and terrain slope were negatively related to the probability of occurrence of C. orbiculatus. The model was highly discriminatory, with an area under the receiver-operating characteristic curve of 0Æ91. 4. Distance from introduction locus and slope were also important in the models for the pioneer and established zones respectively. 5. The pioneer zone model also indicated a negative relationship with elevation and the established zone model indicated a positive relationship with local topographic position, but these models were less discriminatory. 6. Synthesis and applications. Distance from introduction locus was the most powerful variable examined, suggesting anenduringlegacyof introductionfor the currentdistributionofC. orbiculatus. The varying results in the three zones highlight the importance of accounting for both introduction history and uneven propagule pressure in studies of observed invasive species distributions. The observed relationships with distance and elevation suggest that land managers should prepare for C. orbiculatus to expandits distribution in the regionover timeandwith awarming climate.

Ball, B.A., Bradford, M.A. 2009. Nitrogen and Phosphorus Release from Mixed Litter Layers is Lower than Predicted from Single Species Decay. Ecosystems 12: 87-100

Abstract
Ecosystem-level nutrient dynamics during decomposition are often estimated from litter monocultures. If species effects are additive, we can statistically predict nutrient dynamics in multispecies systems from monoculture work, and potential consequences of species loss. However, if species effects are dependent on interactions with other litter species (that is, non-additive), predictions based on monoculture data will likely be inaccurate. We conducted a 3-year, full-factorial, mixed-litter decomposition study of four dominant tree species in a temperate forest and measured nitrogen and phosphorus dynamics to explore whether nutrient dynamics in mixtures were additive or non-additive. Following common approaches, we used litterfall data to predict nutrient dynamics at the ecosystem-level. In mixtures, we observed non-additive effects of litter mixing on nutrient dynamics: the presence of nutrient-rich species in mixture facilitated nutrient release, whereas nutrient-poor species facilitated nutrient retention. Fewer nutrients were released from mixtures containing high-quality litter, and more immobilized from mixtures containing low-quality litter, than predicted from monocultures, creating a difference in overall nutrient release between predicted and actual dynamics in litter mixtures. Nutrient release at the ecosystem-level was greatly overestimated when based on monocultures because the effect of species interactions on nutrient immobilization was not accounted for. Our data illustrate that the identity of species in mixtures is key to their role in non-additive interactions, with repercussions for mineral nutrient availability and storage. These results suggest that predictions of ecosystem-level nutrient dynamics using litter monoculture data likely do not accurately represent actual dynamics because the effects of litter species interactions are not incorporated.

Ball, B.A., Bradford, M.A., Coleman, D.C., Hunter, M.D. 2009. Linkages between below and aboveground communities: Decomposer responses to simulated tree species loss are largely additive. Soil Biology and Biochemistry. 40: 155-1163.

Abstract
Inputs of aboveground plant litter influence the abundance and activities of belowground decomposer biota. Litter-mixing studies have examined whether the diversity and heterogeneity of litter inputs affect decomposer communities inways that can be predicted from monocultures. They have mainly attempted to detect non-additive effects of litter mixing, although individual species effects (additivity) as well as species interactions (non-additivity) may alter decomposition rates. To determine potential impacts of plant species loss on aboveground-decomposer linkages, we assessed both additive and non-additive effects of litter mixing on decomposer communities. A full-factorial litterbag experiment with leaves from four deciduous tree species was conducted, to assess responses of bacteria, fungi, nematodes, and microarthropods. Data were analyzed using a statistical method that first looked for additive effects based on the presence or absence of species and then any significant species interactions. We observed almost exclusively additive effects of all four litter species on decomposer biota, with each species exerting effects on different aspects of the community. These results imply that the consequences of species loss for the decomposer community will be largely predictable from knowledge of single species litter dynamics. The two species at opposite ends of the quality spectrum exerted the most effects. Highquality Liriodendron tulipifera supported a more diverse arthropod community and drove bottom-up effects on the decomposer food web. Low-quality Rhododendron maximum had negative effects on most groups of biota. Litter of mid-quality species exerted fewer effects. The influence of litter species richness on the Tylenchidae (nematodes) was the only non-additive effect of litter mixing. Together, these data demonstrate an effect of plant community composition on decomposer biomass, abundance, and diversity, confirming a link between above and belowground communities. We were able to identify the species to which the decomposer community is most sensitive, aiding predictions of the consequences of the loss of these dominant species on the decomposer community, with potential feedbacks for organic matter and nutrient turnover.

Benstead, J., Rosemond, A., Cross, W., Wallace, J., Eggert, S., Suberkropp, K., Gulis, V., Greenwood, J., Tant, C. 2009. Nutrient enrichment alters storage and fluxes of detritus in a headwater stream ecosystem. Ecology, 90(9):2556-2566

Abstract
Responses of detrital pathways to nutrients may differ fundamentally from pathways involving living plants: basal carbon resources can potentially decrease rather than increase with nutrient enrichment. Despite the potential for nutrients to accelerate heterotrophic processes and fluxes of detritus, few studies have examined detritus–nutrient dynamics at whole-ecosystem scales. We quantified organic matter (OM) budgets over three consecutive years in two detritus-based Appalachian (USA) streams. After the first year, we began enriching one stream with low-level nitrogen and phosphorus inputs. Subsequent effects of nutrients on outputs of different OM compartments were determined using randomized intervention analysis. Nutrient addition did not affect dissolved or coarse particulate OM export but had dramatic effects on fine particulate OM (FPOM) export at all discharges relative to the reference stream. After two years of enrichment, FPOM export was 340% higher in the treatment stream but had decreased by 36% in the reference stream relative to pretreatment export. Ecosystem respiration, the dominant carbon output in these systems, also increased in the treatment stream relative to the reference, but these changes were smaller in magnitude than those in FPOM export. Nutrient enrichment accelerated rates of OM processing, transformation, and export, potentially altering food-web dynamics and ecosystem stability in the long term. The results of our large-scale manipulation of a detrital ecosystem parallel those from analogous studies of soils, in which net loss of organic carbon has often been shown to result from experimental nutrient addition at the plot scale. Streams are useful model systems in which to test the effects of nutrients on ecosystem-scale detrital dynamics because they allow both the tracking of OM conversion along longitudinal continua and the integrated measurement of fluxes of transformed material through downstream sites.

Bradford, M.A., DeVore, J.L., Maerz, J.C., McHugh, J.V., Smith, C.L., Strickland, M.S. 2009. Native, insect herbivore communities derive a significant proportion of their carbon from a widespread invader of forest understories. Biol Invasions.

Abstract
Research on natural enemies demonstrates the potential for exotic plants to be integrated into foodwebs through the activities of native herbivores. The quantitative importance of exotics as a food resource to herbivores is more difficult to ascertain. In addition, some widespread invaders appear to have minimal herbivore loads. Microstegium vimineum is one example. It is an annual, C4 grass that invades forest understories and is widespread across the eastern US. Its invasion alters the structure and composition of forests. We sampled invertebrates in a tree-canopy gap and under canopy area, and used the unique carbon isotope value of M. vimineum to estimate the quantitative importance of the invader as a food resource relative to native plants. Seven of the eight invertebrate species derived on average [35% of their biomass carbon from M. vimineum, and some individuals representing both ‘chewing’ and ‘sucking’ feeding guilds derived their biomass carbon exclusively from M. vimineum. Our results show that M. vimineum can be a significant food resource for a multi-species, multi-guild, assemblage of native, invertebrate herbivores. Future work is required to assess whether M. vimineum is acquiring herbivores in other parts of its introduced range, and if so what might be the ecological consequences.

Bradford, M.A., et al. 2009. Decreased mass specific respiration under experimental warming is robust to the microbial biomass method employed. Ecology Letters, 12: E15-E18.

Abstract
Hartley et al. question whether reduction in Rmass, under experimental warming, arises because of the biomass method. We show the method they treat as independent yields the same result. We describe why the substrate-depletion hypothesis may not solely explain observed responses, and urge caution in interpretation of the seasonal data.

Brookshite, E.N.J, Valett, H.M., Gerber, S. 2009. Maintenance of terrestrial nutrient loss signatures during in-stream transport. The Ecological Society of America, 90(2): 293-299

Abstract
Small streams account for the majority of channel length in river basins worldwide and are the primary conveyors of terrestrial nutrients to rivers and ultimately the oceans. The controls of stream nutrient fluxes, however, are debated. Classical models emphasize that nutrient transport in streams integrates nutrient cycling in the terrestrial watershed while others argue that in-stream processes control nutrient flux. Recent studies have shown that in-stream cycling can be important in determining downstream nutrient fluxes, but results have not been reconciled with mass–balance calculations at the small watershed scale. Here we use a simple analytical framework to assess nutrient cycling in streams and show that, under most conditions, longitudinally static nutrient concentrations reflect in-stream biotic balance between uptake and regeneration and groundwater inputs. Using measures of nutrient concentrations in small streams across four biomes, we provide evidence for generality of biogeochemical steady state (inputs¼outputs) in stream ecosystems: overall, longitudinal profiles were flat for nitrogen and phosphorus and were similar in concentration to soil and ground waters. Deviation from flat longitudinal profiles was associated with seasonal or successional biomass growth and small groundwater inputs relative to in-stream sink strength. We conclude that streams tend strongly toward nutrient balance, allowing use of their chemistry as an integrated measure of terrestrial nutrient losses.

Camp, C., Peterman, W., Milanovich, J., Lamb, T., Maerz, J., Wake, D. 2009. A new genus and species of lungless salamander (family Plethodontidae) from the Appalachian highlands of the south-eastern United States. Journal of Zoology, 279(1): 86-94

Abstract
We describe a striking new species of the lungless salamander family Plethodontidae from the Appalachian foothills of northern Georgia, USA. This miniature species, c. 25–26mm (adult standard length), is so distinctive genetically and morphologically that we erect a new genus, the first new genus of amphibian described from the US in nearly 50 years. It is unique among plethodontids from eastern North America in displaying sexual colour dimorphism. Although certain miniaturized plethodontids exhibit a reduced number (four) of digits on the pes, this species possesses a full complement of five toes. A plethodontid phylogeny derived from mitochondrial and nuclear DNA sequences places it in the tribe Spelerpini as the sister taxon to Eurycea. Genetic divergence between the new species and Eurycea for the nuclear gene Rag-1 (4.7%) is among the higher levels observed between long-established spelerpine genera (2.6–5.3%). This new form appears to be rare and is of immediate conservation concern.

Carter, T., C.R. Jackson, A. Rosemond, C. Pringle, D. Radcliffe, W. Tollner, J. Maerz, D. Leigh. A. Trice. 2009. Beyond the urban gradient: barriers and opportunities for timely studies of urbanization effects on aquatic ecosystems. Journal of the North American Benthological Society, 28(4):1038-1050

Abstract
Many studies have shown that streams degrade in response to urbanization in the watershed. These studies often are based on use of biotic and abiotic variables to measure stream health across a gradient of land cover/land use. The results of these studies can be applied to other urban systems, but often fail to provide a mechanistic understanding of the urban impact, in part, because of the nature of the experimental design. We analyzed the advantages and disadvantages of using environmental gradient studies to further understanding of urban stream systems. We also evaluated alternative experimental design approaches, including best management practice monitoring, long-term watershed studies, pairedwatershed studies, and before–after control–impact studies, which could be used to complement the gradient approach. We illustrate these theoretical discussions with an urban paired-watershed case study in the Etowah watershed in northern Georgia. Our goal is to move experimental designs in a direction that will further our mechanistic understanding of the effects of existing urbanization on aquatic ecosystems and will provide opportunities to evaluate stream responses to environmentally sensitive urban land cover.

Clark, J.S. and M. H. Hersh. 2009. Inference when multiple pathogens affect multiple hosts: Bayesian model selection. Bayesian Analysis 4:337 - 366

Abstract
A large literature concerns the epidemiology of single pathogens on single hosts. Yet in some environmental applications, such as fungal pathogens of forest tree seedlings, the \one host-one pathogen" paradigm may not be applicable. Multiple potential pathogens are often found in a single individual and/or multiple hosts share the same pathogens. Understanding diversity requires techniques to infer how multiple pathogens might regulate multiple hosts and to predict how im- pacts might vary with the environment. Here we present a hierarchical framework for the case where there is detection information based on multiple sources (cul- tures, gene sequencing, and survival observations), and the inference problem in- cludes not only parameters that describe environmental in°uences on pathogen in- cidence, infection, and host survival, but also on latent states themselves{pathogen incidence at a site and infection statuses of hosts. Due to the large size of the model space, we develop a reversible jump Markov chain Monte Carlo approach to select models, estimate posterior distributions, and predict environmental in°uences on host survival. We demonstrate with application to a data set involving fungal pathogens on tree hosts, where data include host survival and fungal detection using cultures and DNA sequencing.

Colchero, F., R. A. Medellin, J. S. Clark, R. Lee, and G. G. Katul. 2009. Predicting population survival under future climate change: density dependence, drought and extraction in an insular bighorn sheep. Journal of Animal Ecology, 78:666-673.

Abstract
1. Our understanding of the interplay between density dependence, climatic perturbations, and conservation practices on the dynamics of small populations is still limited. This can result in uninformed strategies that put endangered populations at risk. Moreover, the data available for a large number of populations in such circumstances are sparse and mined with missing data. Under the current climate change scenarios, it is essential to develop appropriate inferential methods that can make use of such data sets. 2. We studied a population of desert bighorn sheep introduced to Tiburon Island, Mexico in 1975 and subjected to irregular extractions for the last 10 years. The unique attributes of this population are absence of predation and disease, thereby permitting us to explore the combined effect of density dependence, environmental variability and extraction in a ‘controlled setting.’ Using a combination of nonlinear discrete models with long-term field data, we constructed three basic Bayesian state space models with increasing density dependence (DD), and the same three models with the addition of summer drought effects. 3. We subsequently used Monte Carlo simulations to evaluate the combined effect of drought, DD, and increasing extractions on the probability of population survival under two climate change scenarios (based on the Intergovernmental Panel on Climate Change predictions): (i) increase in drought variability; and (ii) increase in mean drought severity. 4. The population grew from 16 individuals introduced in 1975 to close to 700 by 1993. Our results show that the population’s growth was dominated by DD, with drought having a secondary but still relevant effect on its dynamics. 5. Our predictions suggest that under climate change scenario (i), extraction dominates the fate of the population, while for scenario (ii), an increase in mean drought affects the population’s probability of survival in an equivalent magnitude as extractions. Thus, for the long-term survival of the population, our results stress that a more variable environment is less threatening than one in which the mean conditions become harsher. Current climate change scenarios and their underlying uncertainty make studies such as this one crucial for understanding the dynamics of ungulate populations and their conservation.

Cressie, N., C. A. Calder, J. S. Clark, J. M. Ver Hoef, and C. K. Wikle. 2009. Accounting for uncertainty in ecological analysis: the strengths and limitations of hierarchical statistical modeling. Ecological Applications, 19:553-570.

Abstract
Analyses of ecological data should account for the uncertainty in the process(es) that generated the data. However, accounting for these uncertainties is a difficult task, since ecology is known for its complexity. Measurement and/or process errors are often the only sources of uncertainty modeled when addressing complex ecological problems, yet analyses should also account for uncertainty in sampling design, in model specification, in parameters governing the specified model, and in initial and boundary conditions. Only then can we be confident in the scientific inferences and forecasts made from an analysis. Probability and statistics provide a framework that accounts for multiple sources of uncertainty. Given the complexities of ecological studies, the hierarchical statistical model is an invaluable tool. This approach is not new in ecology, and there are many examples (both Bayesian and non-Bayesian) in the literature illustrating the benefits of this approach. In this article, we provide a baseline for concepts, notation, and methods, from which discussion on hierarchical statistical modeling in ecology can proceed. We have also planted some seeds for discussion and tried to show where the practical difficulties lie. Our thesis is that hierarchical statistical modeling is a powerful way of approaching ecological analysis in the presence of inevitable but quantifiable uncertainties, even if practical issues sometimes require pragmatic compromises.

Davis, J.M., Rosemond, A.D., Eggert, S.L., Crossa, W.F., Wallace, J.B. 2009. Long-term nutrient enrichment decouples predator and prey production. PNAS. 107(1): 121-126

Abstract
Increased nutrient mobilization by human activities represents one of the greatest threats to global ecosystems, but its effects on ecosystemproductivity can differ depending onfoodwebstructure. When this structure facilitates efficient energy transfers to higher trophic levels, evidence from previous large-scale enrichments suggests that nutrients can stimulate the production of multiple trophic levels. Here we report results from a 5-year continuous nutrient enrichment of a forested stream that increased primary consumer production, but not predator production. Because of strong positive correlations between predator and prey production (evidence of highly efficient trophic transfers) under reference conditions, we originally predicted that nutrient enrichment would stimulate energy flow to higher trophic levels. However, enrichment decoupled this strong positive correlation and produced a nonlinear relationship between predator and prey production. By increasing the dominance of large-bodied predator-resistant prey, nutrient enrichment truncated energy flow to predators and reduced food web efficiency. This unexpected decline in food web efficiency indicates that nutrient enrichment, a ubiquitous threat to aquatic ecosystems, may have unforeseen and unpredictable effects on ecosystem structure and productivity.

Dyer, J.M. 2009. Assessing topographic patterns in moisture use and stress using a water balance approach. Landscape Ecol 24:391-403.

Abstract
Through its control on soil moisture patterns, topography's role in influencing forest composition is widely recognized. This study addresses shortcomings in traditional moisture indices by employing a water balance approach, incorporating topographic and edaphic variability to assess fine-scale moisture demand and moisture availability. Using GIS and readily available data, evapotranspiration and moisture stress are modeled at a fine spatial scale at two study areas in the US (Ohio and North Carolina). Model results are compared to field-based soil moisture measurements throughout the growing season. A strong topographic pattern of moisture utilization and demand is uncovered, with highest rates of evapotranspiration found on south-facing slopes, followed by ridges, valleys, and north-facing slopes. Southfacing slopes and ridges also experience highest moisture deficit. Overall higher rates of evapotranspiration are observed at the Ohio site, though deficit is slightly lower. Based on a comparison between modeled and measured soil moisture, utilization and recharge trends were captured well in terms of both magnitude and timing. Topographically controlled drainage patterns appear to have little influence on soil moisture patterns during the growing season. In addition to its ability to accurately capture patterns of soil moisture in both high-relief and moderate-relief environments, a water balance approach offers numerous advantages over traditional moisture indices. It assesses moisture availability and utilization in absolute terms, using readily available data and widely used GIS software. Results are directly comparable across sites, and although output is created at a fine-scale, the method is applicable for larger geographic areas. Since it incorporates topography, available water capacity, and climatic variables, the model is able to directly assess the potential response of vegetation to climate change.

Elliott, K. J., J. M. Vose, and R. L. Hendrick. 2009. Long-term effects of high intensity prescribed fire on vegetation dynamics in the wine spring creek watershed, Western North Carolina, USA. Fire Ecology, 5(2): 66-85.

Abstract
We examined the long-term effects of a prescribed fire in a southern Appalachian watershed in Nantahala National Forest, western North Carolina, USA. Fire was prescribed in 1995 on this site by forest managers to restore a degraded pine (Pinus spp.)-hardwood community, specifically to stimulate forage production, promote pine and oak (Quercus spp.) regeneration, and increase plant diversity. Before and after the prescribed fire, permanent plots were sampled across a south-facing hillslope, which corresponded to three community types: mesic, near-stream cove (riparian); dry, mixed-oak (mid-slope); and xeric, pine-hardwood (ridge). In an earlier paper, we reported the first two years of post-burn vegetation response from this prescribed burn. In our current study, we compared the pre-burn (1994) forest condition with 10 years post-burn (2005) vegetation measurements to determine the effects of fire on the mortality and regeneration of overstory trees, understory shrubs, and herbaceous-layer species. Overstory mortality was high immediately after the burn at the ridge location and ten years after the fire. Mortality of pitch pine (Pinus rigida Miller) (91.8 %) and hickory (Carya spp.) (77.5 %) reduced overstory basal area from 26.97 m2 ha-1 pre-burn to 18.86 m2 ha-1 post-burn in 1995 and to 9.13 m2 ha-1 in 2005. At the mid-slope and riparian locations, no significant overstory mortality occurred over time. Understory density was significantly higher 10 years after the burn (2005) than pre-burn, and basal area had returned to pre-burn levels. Density of mountain laurel (Kalmia latifolia L.), black huckleberry (Gaylussacia baccata [Wang.] K. Koch), and blueberry (Vaccinium spp.) had increased due to prolific sprouting. The prescribed fire had varying effects on diversity across the hillslope gradient over time. On the ridge, overstory diversity declined following the fire (H’basal area = 1.14 in 1994, H’basal area = 0.75 in 1995, and H’basal area = 0.80 in 2005). Diversity significantly increased in the herbaceous layer and remained higher than pre-burn conditions through 2005 (H’cover = 1.02 in 1994, H’cover = 1.97 in 1995, and H’cover = 2.25 in 2005). For the mid-slope and riparian positions, no change in diversity was observed in the overstory, understory or herbaceous layer.

Fraterrigo, J.M., Pearson, S.M., Turner, M.G. 2009. Joint effects of habitat configuration and temporal stochasticity on population dynamics. Landscape Ecology 24(7): 863-877.

Abstract
Habitat configuration and temporal stochasticity in the environment are recognized as important drivers of population structure, yet few studies have examined the combined influence of these factors. We developed a spatially explicit simulation model to investigate how stochasticity in survival and reproduction influenced population dynamics on landscapes that differed in habitat configuration. Landscapes ranged from completely contiguous to highly fragmented, and simulated populations varied in mean survival probability (0.2, 0.4, 0.8) and dispersal capacity (1, 3, or 5 cells). Overall, habitat configuration had a large effect on populations, accounting for [80% of the variation in population size when mean survival and dispersal capacity were held constant. Stochasticity in survival and reproduction were much less influential, accounting for\1–14% of the variation in population size, but exacerbated the negative effects of habitat fragmentation by increasing the number of local extinctions in isolated patches. Stochasticity interacted strongly with both mean survival probability and habitat configuration. For example, survival stochasticity reduced population size when survival probability was high and habitat was fragmented, but had little effect on population size under other conditions. Reproductive stochasticity reduced population size irrespective of mean survival and habitat configuration, but had the largest effect when survival probability was intermediate and habitat was well connected. Stochasticity also enhanced the variability of population size in most cases. Contrary to expectations, increasing dispersal capacity did not increase population persistence, because the probability of finding suitable habitat within the dispersal neighborhood declined more for the same level of dispersal capacity when fragmentation was high compared to when it was low. These findings suggest that greater environmental variability, as might arise due to climate change, is likely to compound population losses due to habitat fragmentation and may directly reduce population size if reproductive output is compromised. It may also increase variability in population size.

Fraterrigo, J.M., Pearson, S.M., Turner, M.G. 2009. The response of understory herbaceous plants to nitrogen fertilization in forests of different land-use history. Forest Ecology and Management, 257: 2182-2188.

Abstract
Forests growing on former agricultural land often have reduced frequencies of many native forest herbs compared with forests that were never cleared for agriculture. A leading explanation for this pattern is thatmany forest herbs are dispersal limited, but environmental conditionsmay also hinder colonization. We examined the response of six forest herb taxa (Arisaema triphyllum, Cimicifuga racemosa, Disporum lanuginosum, Osmorhiza spp., Polygonatum spp., and Prenanthes altissima) to nitrogen (N) fertilization in forests with and without an agricultural history to investigate how N availability affects plant performance. The study was conducted in the southern Appalachian Mountains in western North Carolina, USA. There was a significant interaction between land-use history and N treatment for several species. In A. triphyllum and Osmorhiza spp., N fertilization increased aboveground biomass or leaf area more in the post-agriculture site than in the reference site. However, in the reference site, N fertilization depressed aboveground biomass or leaf area in the same taxa, as well as in C. racemosa. The foliar N concentration of these three taxa was elevated in fertilized plots regardless of land-use history, and there was no indication that the light environment differed among plots. These results suggest that some plants growing in post-agricultural stands may be N limited, whereas undisturbed stands in this region appear to be approaching N saturation. Thus, environmental conditions, and particularly N availability, may be an obstacle to the restoration of forest herb communities.

Hales, T., Ford, C., Hwang, T., Vose, J., Band, L. Topographic and ecologic controls on root reinforcement. Journal of Geophysical Research, 114: F03013

Abstract
Shallow landslides are a significant hazard in steep, soil-mantled landscapes. During intense rainfall events, the distribution of shallow landslides is controlled by variations in landscape gradient, the frictional and cohesive properties of soil and roots, and the subsurface hydrologic response. While gradients can be estimated from digital elevation models, information on soil and root properties remains sparse. We investigated whether geomorphically controlled variations in ecology affect the spatial distribution of root cohesion by measuring the distribution and tensile strength of roots from soil pits dug downslope of 15 native trees in the southern Appalachian Mountains, North Carolina, United States. Root tensile strengths from different hardwood tree species were similar and consistently higher than the only native shrub species measured (Rhododendron maximum). Roots were stronger in trees found on noses (areas of divergent topography) relative to those in hollows (unchanneled, convergent topography) coincident with the variability in cellulose content. This cellulose variability is likely related to topographic differences in soil water potential. For all species, roots were concentrated close to the soil surface, with roots in hollows being more evenly distributed in the soil column than those on noses. Trees located on noses had higher mean root cohesion than those in hollows because of a higher root tensile force. R. maximum had the shallowest, weakest roots suggesting that recent expansion of this species due to fire suppression has likely lowered the root cohesion of some hollows. Quantification of this feedback between physiologic controls on root growth and slope hydrology has allowed us to create a curvature-based model of root cohesion that is a significant improvement on current models that assume a spatially averaged value.

Hall, R.O., et all. 2009. Nitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake. Limnol. Oceanogr. 54(3): 653-665.

Abstract
We measured uptake length of 15NO{3 in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO{3 uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban–urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO{3 concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO{3 uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79% of the variation in log uptake length (SWtot). Uptake length increased with specific discharge (Q/w) and increasing NO{3 concentrations, showing a loss in removal efficiency in streams with high NO{3 concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO{3 removal. The fraction of catchment area as agriculture and suburban– urban land use weakly predicted NO{3 uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO{3 uptake lengths via directly increasing both gross primary production and NO{3 concentration. Gross primary production shortened SWtot, while increasing NO{3 lengthened SWtot resulting in no net effect of land use on NO{3 removal.

Hazelton, P.D., Grossman, G.D. 2009. The effects of turbidity and an invasive species on foraging success of rosyside dace (Clinostomus funduloides). Freshwater Biology, 54: 1977-1989

Abstract
1. Habitat degradation and biological invasions are important threats to fish diversity worldwide. We experimentally examined the effects of turbidity, velocity and intra- and interspecific competition on prey capture location, reactive distance and prey capture success of native rosyside dace (Clinostomus funduloides) and invasive yellowfin shiners (Notropis lutipinnis) in Coweeta Creek, North Carolina, U.S.A. 2. Increased turbidity and velocity produced significant decreases in the number of prey captured forward of the fish’s location. It is possible that this represents an increase in the amount of energy expended per prey captured. 3. We used Akaike’s Information Criterion (AIC) to evaluate competing explanatory models for reactive distance (10 generalised linear models, GLM) and prey capture success (9 generalised linear mixed models, GLMM). 4. Reactive distance decreased by 12% with an increase from 2 to 4 conspecifics, whereas a 10 NTU increase in turbidity reduced reactive distance by 9%. Capture success was affected by velocity, dominance and competition, and varied among species. A 6 cm s)1 increase in velocity produced a 28% decline in capture probability; however, dominant fish were 3.2 times more likely to capture a prey item than non-dominant fish. Yellowfin shiners only were 0.62 times as likely to capture a prey item as rosyside dace. Both intraand interspecific competition reduced capture probability, and fish in high density intraspecific or interspecific trials were 0.46 times and 0.44 times as likely to capture prey, respectively, as fish in two fish intraspecific trials. 5. These results suggest behavioural variables are as important as physical factors in determining reactive distance and capture probability by these minnows.

Hazelton, P.D., Grossman, G.D. 2009. Turbidity, velocity and interspecific interactions affect foraging behaviour of rosyside dace (Clinostomus funduloides) and yellowfin shiners (Notropis lutippinis). Ecology of Freshwater Fish, 18:427-436

Abstract
Fish diversity is strongly affected by habitat degradation (e.g., increased turbidity) and invasive species. We examined the effects of turbidity, velocity, length, dominance and intra- and interspecific competition on focal point depth, movement rate, dominance and aggression rate in native rosyside dace (Clinostomus funduloides) and invasive yellowfin shiners (Notropis lutipinnis) in a southern Appalachian stream (NC, USA). We compared results for intra- and interspecific groups of fishes at two densities (two and four fishes), three turbidity levels (10, 20 and 30 nephelometric turbidity units), and two velocities (12, 18 cms-1). Dominance was significantly correlated with length in intraspecific groups of both species, and dominant fish held more profitable foraging positions about 75% of the time. Yellowfin shiners were dominant more often than rosyside dace in interspecific trials. Akaike’s Information Criterion indicated that models containing turbidity, velocity, species and intraspecific competition, explained the greatest amount of information in focal point depth data. By contrast, movement and aggression rates were best explained by models based on dominance and velocity. Finally, aggression rate was best explained by models containing fish length and turbidity. These results indicate that habitat degradation, intra- and interspecific interactions influence the foraging behaviour and future success of these species in the Little Tennessee River drainage.

Horton, J. L., Barton D. Clinton, John F. Walker, Colin M. Beier, and Erik T. Nilsen 2009. Variation in Soil and Forest Floor Characteristics Along Gradients of Ericaceous, Evergreen Shrub Cover in the Southern Appalachians. Castanea 74(4): 340-252.

Abstract
Ericaceous shrubs can influence soil properties in many ecosystems. In this astudy, we examined how soil and forest floor properties vary among sites with different aericaceous evergreen shrub basal area in the southern Appalachian mountains. We randomly alocated plots along transects that included open understories and understories with varying aamounts of Rhododendron maximum (rosebay rhododendron) and Kalmia latifolia (mountain alaurel) at three sites. The three sites were a mid-elevation ridge, a low-elevation cove, and a ahigh-elevation southwest-facing slope. Basal area of R. maximum was more correlated with soil aproperties of the forest floor than was K. latifolia. Increasing R. maximum basal area was acorrelated with increasing mass of lower quality litter and humus as indicated by higher C:N aratios. Moreover, this correlation supports our prediction that understory evergreen shrubs may ahave considerable effect on forest floor resource heterogeneity in mature stands.

Hwang, T., Band, L., Hales, T. Ecosystem processes at the watershed scale: Extending optimality theory from plot to catchment. Water Resources Research, 45: W11425.

Abstract
The adjustment of local vegetation conditions to limiting soil water by either maximizing productivity or minimizing water stress has been an area of central interest in ecohydrology since Eagleson’s classic study. This work has typically been limited to consider one-dimensional exchange and cycling within patches and has not incorporated the effects of lateral redistribution of soil moisture, coupled ecosystem carbon and nitrogen cycling, and vegetation allocation processes along topographic gradients. We extend this theory to the hillslope and catchment scale, with in situ and downslope feedbacks between water, carbon and nutrient cycling within a fully transient, distributed model. We explore whether ecosystem patches linked along hydrologic flow paths as a catena evolve to form an emergent pattern optimized to local climate and topographic conditions. Lateral hydrologic connectivity of a small catchment is calibrated with streamflow data and further tested with measured soil moisture patterns. Then, the spatial gradient of vegetation density within a small catchment estimated with fine-resolution satellite imagery and field measurements is evaluated with simulated vegetation growth patterns from different root depth and allocation strategies as a function of hillslope position. This is also supported by the correspondence of modeled and field measured spatial patterns of root depths and catchmentlevel aboveground vegetation productivity.We test whether the simulated spatial pattern of vegetation corresponds to measured canopy patterns and an optimal state relative to a set of ecosystem processes, defined as maximizing ecosystem productivity and water use efficiency at the catchment scale. Optimal carbon uptake ranges show effective compromises between multiple resources (water, light, and nutrients), modulated by vegetation allocation dynamics along hillslope gradient.

Ibanez, I., Clark, J.S., Dietze, M.C. 2009. Estimating colonization potential of migrant tree species. Global Change Biology. 15: 1173-1188

Abstract
Plant populations migrating in response to climate change will have to colonize established communities. Even if a population disperses to a new region with a favorable climate, interactions with other species may prevent its establishment and further spread. The potential of these species to grow along with residents will be a critical factor controlling their response to climate change. To determine the capacity of migrating species to colonize established communities we conducted extensive long-term transplant experiments where potential tree migrant species, i.e. species within ‘migration range,’ were planted side by side with resident ones. Potential immigrants were selected to be representative species of their native communities. For both groups, residents and potential migrants (17 species), we compared their growth response along gradients in soil moisture and light availability. Rather than manipulate climate directly, we exploited natural microclimatic gradients and the fluctuations in climate that occurred during the 5-year experiment. Experimental results were used to estimate growth in the context of novel climate and relevant establishment factors. Results suggest that potential immigrant species had similar growth rates in the new environment than those from resident species ensuring their ability to establish in the area. However, contrary to our expectations, the soil moisture requirements for the immigrant group were similar to those of the resident species. These results could have major implications for vegetation changes under the predicted drier climate for the region. If it is the case that neither resident species nor potential migrants are able to maintain stable populations, the region may experience a decline in local biodiversity.

James S. Clark. 2009. Beyond Neutral Science. Trends in Ecology and Evolution, 24 (1): 8-15

Abstract
Biodiversity science is unusual in that an emerging paradigm is not based on a specific process, but rather depends largely on stochastic elements, perceived as neutral forces. Here I suggest that these forces, which have been justified, in part, by the concepts of symmetry and equalizing mechanisms, have application to the understanding of stochastic models but do not constitute forces that operate in nature. Another process now regularly classified as a neutral force, limited dispersal, represents a fundamental demographic process that is not neutral with respect to species differences, but rather differs among species in important ways. Finally, I suggest that the dramatic shift in ecological research to focus on neutrality could have a cost in terms of scientific understanding and relevance to real biodiversity threats.

Knoepp, J.D., Clinton, B.D. Riparian zones in southern Appalachian headwater catchments: Carbon and nitrogen responses to forest cutting. Forest Ecology and Management 258(10): 2282-2293.

Abstract
There is little understanding about the role eastern US forested headwater riparian areas play in protecting aquatic habitats and water quality from impacts of side slope forest harvest. To better understand this important riparian area function, we selected three sites frommanagement units with a 2-age regeneration silvicultural prescription located on the Nantahala National Forest, North Carolina, USA. Each site was harvested and a riparian buffer was left uncut along the stream. Buffer widths were 10 m and 30 m; we included a 0 m buffer to experimentally determine nutrient and riparian zone responses to forest cutting under extreme conditions. A fourth site was selected to serve as an uncut reference. Transects were established perpendicular to a 200 m stream reach, from streamside to 50 m upslope for intensive study. Forest cutting increased extractable NO3 - at both 0–10 cm and 10–30 cm soil depths compared to pre-treatment concentrations. Soil solution NO3 - concentrations increased only in harvested areas, on all sites; increases were greater in sites with narrowriparian buffers. Stream water NO3 - concentration increased significantly following site harvest only on the 0 m buffer site. Dissolved organic C and N did not respond to harvesting in either soil solution or stream samples. Our results suggest that riparian buffers are effective in removing NO3 - from soil solution prior to its entering the stream.

Knoepp, J.D., Elliott, K.J., Clinton, B.D., Vose, J.M. 2009. Effects of prescribed fire in mixed oak forests of the southern Appalachians: forest floor, soil, and soil solution nitrogen responses. Journal oj the Torrey Botanical Society, 136(3): 380-391

Abstract
We examined nutrient cycling responses to prescribed fire on three sub-mesic, mixed-oak sites located in the Blue Ridge Physiographic province of the southern Appalachian Mountains: Alarka Laurel Branch (AL), Robin Branch (RB), and Roach Mill Branch (RM). Each study site was located within a sub-watershed that drained a first order stream. Our objective was to quantify the effects of prescribed burning on forest floor mass, nitrogen and carbon pools; and soil and soil water available nitrogen. Each site included a burned and unburned control area; both burned and control areas were sampled before and after burning. Within each plot, we sampled forest floor mass, carbon and nitrogen, soil and soil solution nitrate (NO3-N) and ammonium (NH4-N) concentrations before and after the prescribed burns. All prescribed fires were conducted in the dormant season and were low to moderate intensity. All sites lost a significant amount of forest floor mass due to burning; 82 to 91% of the Oi layer and 26 to 46% of the Oe + Oa layer. Soil NH4-N concentrations increased in surface soils (0-5 cm) only, immediately after burning, but return to pre-burn levels by mid-summer. Burning had no measurable effect on soil solution inorganic nitrogen concentrations. Low levels of solution NO3-N and NH4-N after burning and no change in stream Noi-N concentrations indicated that no inorganic nitrogen was lost from these sites.

Kominoski, J.S., Hoellein, T.J., Kelly, J.J., Pringle, C.M. 2009. Does mixing litter of different qualities alter stream microbial diversity and functioning on individual litter species? Oikos. 118: 457 - 463

Abstract
We examined effects of leaf litter quality and species mixing on microbial community diversity and litter processing in a forested headwater stream. Single- and mixed-species litter from dominant tree species (Liriodendron tulipifera, Acer rubrum, Quercus prinus, Rhododendron maximum) were incubated in a southern Appalachian headwater stream. Litter carbon-to-nitrogen ratios (C:N), mass loss, microbial respiration, and microbial community diversity were analyzed on individual litter species after incubation. Initial C:N varied widely among individual litter species, and these differences persisted throughout the 50-day incubation period. Litter C:N of the recalcitrant species R. maximum remained higher than that of all other litter species, and C:N of R. maximum and L. tulipifera increased when both species were present together in a mixture. Although mass loss of individual species was generally unaffected by mixing, microbial respiration was greater on A. rubrum and Q. prinus litter incubated with R. maximum compared to either species alone. Enhanced resource heterogeneity, which was experimentally achieved by litter mixing low- and higher-quality litter species, resulted in apparent shifts in microbial community diversity on individual litter species. Responses of bacterial and fungal community diversity to litter mixing varied among individual litter species. Our results suggest that changes in tree species composition in riparian forests and subsequent changes in litter resource heterogeneity could alter stream microbial community diversity and function. As bacteria and fungi are important decomposers of plant litter in aquatic ecosystems, resource-dependent changes in microbial communities could alter detrital processing dynamics in streams.

Kominoski, J.S., Pringle, C.M. 2009. Resource-consumer diversity: testing the effects of leaf litter species diversity on stream macroinvertebrate communities. Freshwater Biology. 54: 1461-1473

Abstract
1. Understanding relationships between resource and consumer diversity is essential to predicting how changes in resource diversity might affect several trophic levels and overall ecosystem functioning. 2. We tested for the effects of leaf litter species diversity (i.e. litter mixing) on litter mass remaining and macroinvertebrate communities (taxon diversity, abundance and biomass) during breakdown in a detritus-based headwater stream (North Carolina, U.S.A.). We used full-factorial analyses of single- and mixed-species litter from dominant riparian tree species with distinct leaf chemistries [red maple (Acer rubrum), tulip poplar (Liriodendron tulipifera), chestnut oak (Quercus prinus) and rhododendron (Rhododendron maximum)] to test for additivity (single-species litter presence/absence effects) and non-additivity (emergent effects of litter species interactions). 3. Significant non-additive effects of litter mixing on litter mass remaining were explained by species composition, but not richness, and litter-mixing effects were variable throughout breakdown. Specifically, small differences in observed versus expected litter mass remaining were measured on day 14; whereas observed litter mass remaining in mixed-species leaf packs was significantly higher on day 70 and lower on day 118 than expected from data for single-species leaf packs. 4. Litter mixing had non-additive effects on macroinvertebrate community structure. The number of species in litter mixtures (two to four), but not litter species composition, was a significant predictor of the dominance of particular macroinvertebrates (i.e. indicator taxa) within mixed-species packs. 5. In addition, the presence/absence of high- (L. tulipifera) and low-quality (R. maximum) litter had additive effects on macroinvertebrate taxon richness, abundance and biomass. The presence of L. tulipifera litter had both positive (synergistic) and negative (antagonistic) effects on invertebrate taxon richness, that varied during breakdown but were not related to litter chemistry. In contrast, the presence/absence of L. tulipifera had a negative relationship with total macroinvertebrate biomass (due to low leaf mass remaining when L. tulipifera was present and higher condensed and hydrolysable tannins associated with leaf packs lacking L. tulipifera). Macroinvertebrate abundance was consistently lower when R. maximum was present, which was partially explained by litter chemistry [e.g., high concentrations of lignin, condensed tannins, hydrolysable tannins and total phenolics and high carbon to nutrient (N and P) ratios]. 6. The bottom-up effects of litter species diversity on stream macroinvertebrates and litter breakdown are different, which suggests that structural attributes of macroinvertebrate communities may only partially explain the effects of litter-mixing on organic matter processing in streams. In addition, stream macroinvertebrates colonising decomposing litter are influenced by resource diversity as well as resource availability. Broad-scale shifts in riparian tree species composition will alter litter inputs to streams, and our results suggest that changes in the diversity and availability of terrestrial litter may alter stream food webs and organic matter processing.

Kominoski, J.S., T.J. Hoellein, C.J. Leroy, C.M. Pringle, C.M. Swan. 2010. Beyond Species Richness: Expanding Biodiversity Ecosystem Functioning Theory In Detritus-Based Streams. River Research and Applications 26:67-75.

Abstract
Initial research informing biodiversity-ecosystem functioning (B-EF) theory focused largely on terrestrial plant species richness effects on productivity. Recent studies in stream ecosystems have further advanced understanding of B-EF beyond species richness by testing effects of species diversity (richness and composition) at multiple trophic levels. Recent meta-analyses of stream B-EF studies across multiple trophic levels found stronger evidence for composition- than richness-functioning relationships. Here, we further examine effects of resource and consumer diversity on stream organic matter processing (OMP) to identify general patterns and potential mechanisms of non-additivity across spatial and temporal heterogeneity. We also review multi-trophic consumer response patterns to resource diversity to assess how consumer diversity responses compare to independent resource and consumer effects on OMP in streams. Consistent emergent patterns include: (1) Top-down (i.e. consumer) diversity effects are common among vertebrate, invertebrate, and microbial trophic levels and are generally explained by species evenness; (2) Bottom-up (i.e. resource) diversity effects are mediated by species evenness and vary both spatially and temporally; (3) Consumer responses to resource diversity that best explain resource diversity effects are predominantly seen at the microbial level. Resource and consumer diversity effects are driven by dominance of functionally distinct taxa. However, responses of consumers to resource diversity only partially explain resource diversity effects, suggesting functional differences between how naturally colonizing and manipulated consumer assemblages use OM resources. The challenges facing general ecology and the advancement of B-EF theory include an improved understanding of how environmental heterogeneity and temporal and spatial variation influence B-EF patterns.

Lessard, J. P., R. R. Dunn, and N. J. Sanders. 2009. Temperature-mediated coexistence in temperate forest ant communities. Insectes Scoiaux, 56: 149-156.

Abstract
Patterns of ant species diversity are well documented and yet the mechanisms promoting species coexistence among communities are often elusive. Two emerging hypotheses that account for coexistence in ant communities are the discovery-dominance tradeoff and the dominance-thermal tolerance tradeoff. Here we used behavioural assays and community-level sampling from ant assemblages in the southern Appalachians, USA to test for the discovery-dominance and dominance-thermal tolerance tradeoffs. Species that were behaviorally dominant during interspecific interactions tended to forage in a narrow window of generally warmer temperatures, whereas subordinate species tended to forage in a wide range of temperatures, including colder temperatures. Species that foraged at lower temperature tended to be behaviourally subordinate, suggesting that a dominance-thermal tolerance tradeoff promotes coexistence in this system. Species richness was positively related to site average annual temperature and within-site variation in ground temperature, suggesting that temperature also shapes the structure of ant communities and regulates diversity. There was no relationship between the ability of a species to discover food resources and its behavioural dominance, contrary to the predictions of the discovery-dominance tradeoff hypothesis. In sum, our results show that temperature plays numerous roles in promoting regional coexistence in this system.

Marcelo Ardon, Catherine M. Pringle and Susan L. Eggert (2009) Does leaf chemistry differentially affect breakdown in tropical vs temperate streams? Importance of standardized analytical techniques to measure leaf chemistry. Journal of the North American Benthological Society: June 2009, Vol. 28, No. 2, pp. 440-453.

Abstract
Comparisons of the effects of leaf litter chemistry on leaf breakdown rates in tropical vs temperate streams are hindered by incompatibility among studies and across sites of analytical methods used to measure leaf chemistry. We used standardized analytical techniques to measure chemistry and breakdown rate of leaves from common riparian tree species at 2 sites, 1 tropical and 1 temperate, where a relatively large amount of information is available on litter chemistry and breakdown rates in streams (La Selva Biological Station, Costa Rica, and Coweeta Hydrologic Laboratory, North Carolina, USA). We selected 8 common riparian tree species from La Selva and 7 from Coweeta that spanned the range of chemistries of leaf litter naturally entering streams at each site. We predicted that concentrations of secondary compounds would be higher in the tropical species than in the temperate species and that high concentrations of condensed tannins would decrease breakdown rates in both sites. Contrary to our predictions, mean concentration of condensed tannins was significantly greater (2.6×, p < 0.001) for species at Coweeta than for species at La Selva. Concentration of condensed tannins was negatively correlated with breakdown rate among Coweeta species (r = -0.80), not among La Selva species, and negatively correlated when the 2 sites were combined (r = -0.53). Concentrations of structural compounds were strongly correlated with breakdown rate at both sites (Coweeta species, lignin r = -0.94, cellulose r = -0.77; La Selva species, cellulose r = -0.78, C r = -0.73). The chemistries of 8 riparian species from La Selva and 7 riparian species from Coweeta were not as different as expected. Our results underline the importance of standardized analytical techniques when making cross-site comparisons of leaf chemistry.

McMahon, S. M., M. C. Dietze, M. H. Hersh, E. V. Moran, and J. S. Clark. 2009. A predictive framework to understand forest responses to global change. Pages 221-236 in R. Ostfeld and W.H. Schlesinger (eds) Year in Ecology and Conservation Biology 2009.

Abstract
Forests are one of Earth’s critical biomes. They have been shown to respond strongly to many of the drivers that are predicted to change natural systems over this century, including climate, introduced species, and other anthropogenic influences. Predicting how different tree species might respond to this complex of forces remains a daunting challenge for forest ecologists. Yet shifts in species composition and abundance can radically influence hydrological and atmospheric systems, plant and animal ranges, and human populations, making this challenge an important one to address. Forest ecologists have gathered a great deal of data over the past decades and are now using novel quantitative and computational tools to translate those data into predictions about the fate of forests. Here, after a brief review of the threats to forests over the next century, one of the more promising approaches to making ecological predictions is described: using hierarchical Bayesian methods tomodel forest demography and simulating future forests from those models. This approach captures complex processes, such as seed dispersal and mortality, and incorporates uncertainty due to unknown mechanisms, data problems, and parameter uncertainty. After describing the approach, an example by simulating drought for a southeastern forest is offered. Finally, there is a discussion of how this approach and others need to be cast within a framework of prediction that strives to answer the important questions posed to environmental scientists, but does so with a respect for the challenges inherent in predicting the future of a complex biological system.

Metcalf, C.J.E., J. S. Clark, and D. A. Clark. 2009. Tree growth inference and prediction when the point of measurement changes: modelling around buttresses in tropical forests. Journal of Tropical Ecology, 25:1-12.

Abstract
Estimation of tree growth is generally based on repeated diameter measurements. A buttress at the height of measurement will lead to overestimates of tree diameter. Because buttresses grow up the trunk through time, it has become common practice to increase the height of measurement, to ensure that measurements remain above the buttress. However, tapering of the trunk means that increasing measurement height will bias estimates of diameter downward by up to 10% per m of height. This bias could affect inference concerning species differences and climate effects on tree demography and on biomass accumulation. Here we introduce a hierarchical state space method that allows formal integration of data on diameter taken at different heights and can include individual variation, temporal effects or other covariates.Weillustrate our approach using species from Barro Colorado Island, Panama, and La Selva, Costa Rica. Results include trends that are consistent with some of those previously reported for climate responses and changes over time, but differ in relativemagnitude. By including the full data-set and accounting for bias and variation among individuals and over time, our approach allows for quantification of climate responses and the uncertainty associated with measurements and the underlying growth process.

Metcalf, C.J.E., J. S. Clark, and S. M. McMahon. 2009. Overcoming data sparseness and parametric constraints in modeling of tree mortality: a new non-parametric Bayesian model. Canadian Journal of Forest Research, 39, 1677-1687.

Abstract
Accurately describing patterns of tree mortality is central to understanding forest dynamics and is important for both management and ecological inference. However, for many tree species, annual survival of most individuals is high, so that mortality is rare and, therefore, difficult to estimate. Furthermore, tree mortality models have potentially complex suites of covariates. Here, we extend traditional and recent approaches to modeling tree mortality and propose a new nonparametric Bayesian method. Our model is constrained to both reflect and distinguish known relationships between mortality and its two key covariates, diameter and diameter increment growth, but it remains sufficiently flexible to capture a wide variety of patterns of mortality across these covariates. Our model also allows incorporation of outside information in the form of priors, so that increased mortality of large trees can always be formally modeled even when data are sparse. We present results for our nonparametric Bayesian mortality model for maple (Acer spp.), holly (Ilex spp.), sweet gum (Liquidambar styraciflua L.), and tulip-poplar (Liriodendron tulipifera L.) populations from North Carolina, USA.

Mulholland, P.J. 2009. Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification. Limnol. Oceanogr., 54(3): 666–680

Abstract
We measured denitrification rates using a field 15N–NO{3 tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban–urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (Swden) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO{3 removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NHz 4 concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling Swden were specific discharge (discharge / width) and NO{3 concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO{3 concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis–Menten equation. Although Uden increased with increasing NO{3 concentration, the efficiency of NO{3 removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO{3 load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO{3 concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO{3 concentration.

Nedlo, J.E., Martin, T.A., Vose, J.M., Teskey, R.O. 2009. Growing season temperatures limit growth of loblolly pine (Pinus taeda L.) seedlings across a wide geographic transect. Trees-Structure and Function 23(4): 751-759.

Abstract
We grew potted loblolly pine (Pinus taeda L.) seedlings from a single provenance under well watered and fertilized conditions at four locations along a 610 km north–south transect that spanned most of the species range to examine how differences in the above-ground environment would affect growth rate, biomass partitioning and gas exchange characteristics. Across the transect there was an 8.7*C difference in average growing season temperature, and temperature proved to be the key environmental factor controlling growth rate. Biomass growth was strongly correlated with differences in mean growing season temperature (R^2 = 0.97) and temperature sum (R^2 = 0.92), but not with differences in mean daily photosynthetic photon flux density or mean daily vapor pressure deficit. Biomass partitioning between root and shoot was unchanged across sites. There was substantial thermal acclimation of leaf respiration, but not photosynthesis. In mid-summer, leaf respiration rates measured at 25*C ranged from 0.2 lmol m^-2 s^-1 in seedlings from the warmest location to 1.1 lmol m^-2 s^-1 in seedlings from the coolest site. The greatest biomass growth occurred near the middle of the range, indicating that temperatures were sub- and supra-optimal at the northern and southern ends on the range, respectively. However, in the middle of the range, there was an 18% decrease in biomass increment between two sites, corresponding to 1.4*C increase in mean growing season temperature. This suggests that thermal acclimation was insufficient to compensate for this relatively small increase in temperature.

Nilsen, E. T., T. T. Lei, and S. W. Semones. 2009. Presence of understory shrubs constrains carbon gain in sunflecks by advance-regeneration seedlings: evidence from quercus rubra seedlings growing in understory forest patches with or without evergreen shrubs present. International Journal of Plant Science, 170 (6): 735-747.

Abstract
We investigated whether dynamic photosynthesis of understory Quercus rubra L. (Fagaceae) seedlings can acclimate to the altered pattern of sunflecks in forest patches with Rhododendron maximum L. (Ericaceae), an understory evergreen shrub. Maximum photosynthesis (A) and total CO2 accumulated during lightflecks was greatest for 400-s lightflecks, intermediate for 150-s lightflecks, and lowest for 50- and 75-s lightflecks. For the 400-s lightflecks only, maximum A and total CO2 accumulated were significantly lower for seedlings in forest patches with shrubs present (SF) than for seedlings in forest patches without shrubs (F). These effects were found only when Awas calculated on a leaf-area basis because the specific leaf area of seedlings in F patches was 16% lower than it was for seedlings in SF patches. Photosynthesis reached 50% induction in 159 s for seedlings in F patches compared with 226 s for seedlings in SF patches. The faster induction of A for seedlings in F patches resulted in a significantly higher lightfleck use efficiency than for seedlings in SF patches. The inefficient use of lightflecks by Q. rubra seedlings in SF patches may be a primary mechanism by which Q. rubra seedlings are inhibited by subcanopy thickets of R. maximum.

Noel, C., Calder, C., Clark, J., Ver Hoef, J., Wikle, C. 2009. Accounting for uncertainty in ecological analysis: the strengths and limitations of hierarchical statistic modeling. Ecological Applications, 19(3): 553-570

Abstract
Analyses of ecological data should account for the uncertainty in the process(es) that generated the data. However, accounting for these uncertainties is a difficult task, since ecology is known for its complexity. Measurement and/or process errors are often the only sources of uncertainty modeled when addressing complex ecological problems, yet analyses should also account for uncertainty in sampling design, in model specification, in parameters governing the specified model, and in initial and boundary conditions. Only then can we be confident in the scientific inferences and forecasts made from an analysis. Probability and statistics provide a framework that accounts for multiple sources of uncertainty. Given the complexities of ecological studies, the hierarchical statistical model is an invaluable tool. This approach is not new in ecology, and there are many examples (both Bayesian and non-Bayesian) in the literature illustrating the benefits of this approach. In this article, we provide a baseline for concepts, notation, and methods, from which discussion on hierarchical statistical modeling in ecology can proceed. We have also planted some seeds for discussion and tried to show where the practical difficulties lie. Our thesis is that hierarchical statistical modeling is a powerful way of approaching ecological analysis in the presence of inevitable but quantifiable uncertainties, even if practical issues sometimes require pragmatic compromises.

Nuckolls, April E.; Wurzburger, Nina; Ford, Chelcy R.; Hendrick, Ronald L.; Vose, James M.; Kloeppel, Brian D. 2009. Hemlock declines rapidly with hemlock woolly adelgid infestation: impacts on the carbon cycle of southern Appalachian forests. Ecosystems 12(2): 179-190.

Abstract
The recent infestation of southern Appalachian eastern hemlock stands by hemlock woolly adelgid (HWA) is expected to have dramatic and lasting effects on forest structure and function. We studied the short-term changes to the carbon cycle in a mixed stand of hemlock and hardwoods, where hemlock was declining due to either girdling or HWA infestation. We expected that hemlock would decline more rapidly from girdling than from HWA infestation. Unexpectedly, in response to both girdling and HWA infestation, hemlock basal area increment (BAI) reduced substantially compared to reference hardwoods in 3 years. This decline was concurrent with moderate increases in the BAI of co-occurring hardwoods. Although the girdling treatment resulted in an initial pulse of hemlock needle inputs, cumulative litter inputs and O horizon mass did not differ between treatments over the study period. Following girdling and HWA infestation, very fine root biomass declined by 20–40% in 2 years, which suggests hemlock root mortality in the girdling treatment, and a reduction in hemlock root production in the HWA treatment. Soil CO2 efflux (E soil) declined by approximately 20% in 1 year after both girdling and HWA infestation, even after accounting for the intra-annual variability of soil temperature and moisture. The reduction in E soil and the concurrent declines in BAI and standing very fine root biomass suggest rapid declines in hemlock productivity from HWA infestation. The accelerated inputs of detritus resulting from hemlock mortality are likely to influence carbon and nutrient fluxes, and dictate future patterns of species regeneration in these forest ecosystems.

O'Keefe, J.M., Loeb, S.C., Lanham, J.D. Hill, H.S. 2009. Macrohabitat factors affect day roost selection by eastern red bats and eastern pipistrelles in the southern Appalachian Mountains, USA. Forest Ecology and Management, 257: 2868-1763.

Abstract
Although roost sites are critically important to bats,we have few data on macrohabitat factors that affect roost selection by foliage-roosting bats. Such data are needed so that forest managers can make informed decisions regarding conservation of bat roosts. Our objective was to examine roost selection by nonreproductive eastern pipistrelles (Perimyotis subflavus) and red bats (Lasiurus borealis) in a dense deciduous forest undergoing low-intensity timbermanagement in the southern Appalachian Mountains of western North Carolina, USA. During May to August 2004–2006, we radiotracked eight red bats and seven pipistrelles to roosts for 1–14 days (red bats, ¯ x=¼ 4:11 days, n = 19 roosts; pipistrelles, ¯ x = 7 days, n = 15 roosts). We compared roost and random trees or points using paired-sample t-tests for tree and microhabitat characters and logistic regression models of one to three variables for macrohabitat characters. Neither red bats nor pipistrelles selected roosts based on tree or microhabitat characteristics. Red bats used a wide range of stand ages and conditions and, based on our most plausible models for macrohabitat variables, roosted closer than expected ( ¯ x = 70:6m) to linear openings such as gated roads. Pipistrelles only used stands >=72 years in age and roosted closer than expected ( ¯ x = 185:6m) to nonlinear openings and at elevations lower than expected ( ¯ x ¼ 882m). Combined evidence of multiple variables indicated that pipistrelles preferred to roost close to streams. Our results indicate that land managers in the southern Appalachians should maintain a diversity of age classes to provide roosting habitat for both species, and that pipistrelles in particular may benefit from retention of mature stands or buffer zones near perennial streams. Furthermore, non-reproductive red bats and pipistrellesmay prefer to roost near openings to minimize commuting costs when openings comprise a small proportion of a densely forested landscape.

Pangle, L. Vose, J.M., Teskey, R.O. 2009. Radiation use efficiency in adjacent hardwood and pine forests in the southern Appalachians. Forest Ecology and Management, 257: 1034-1042

Abstract
The efficiency with which trees convert photosynthetically active radiation (PAR) to biomass has been shown to be consistent within stands of an individual species, which is useful for estimating biomass production and carbon accumulation. However, radiation use efficiency (e) has rarely been measured in mixed-species forests, and it is unclear how species diversitymay affect the consistency of e, particularly across environmental gradients. We compared aboveground net primary productivity (ANPP), intercepted photosynthetically active solar radiation (IPAR), and radiation use efficiency (e = ANPP/IPAR) between amixed deciduous forest and a 50-year-old white pine (Pinus strobus L.) plantation in the southern Appalachian Mountains. Average ANPP was similar in the deciduous forest (11.5 Mg ha-1 y-1) and pine plantation (10.2 Mg ha-1 y-1), while e was significantly greater in the deciduous fores (1.25 g MJ-1) than in the white pine plantation (0.63 g MJ-1). Our results demonstrate that latesecondary hardwood forests can attain similar ANPP as mature P. strobus plantations in the southern Appalachians, despite substantially less annual IPAR and mineral-nitrogen availability, suggesting greater resource-use efficiency and potential for long-term carbon accumulation in biomass. Along a 260 m elevation gradient within each forest there was not significant variation in e. Radiation use efficiency may be stable for specific forest types across a range of environmental conditions in the southern Appalachian Mountains, and thus useful for generating estimates of ANPP at the scale of individual watersheds.

Peterman, William E., Semlitsch, R.D., 2009. Efficacy of riparian buffers in mitigating local population declines and the effects of even-aged timber harvest on larval salamanders, Forest Ecology and Management, vol. 257, p. 8-14

Abstract
Headwater streams are an important and prevalent feature of the eastern North American landscape. These streams provide a wealth of ecosystem services and support tremendous biological diversity, which is predominated by salamanders in the Appalachian region. Salamanders are ubiquitous throughout the region, contributing a significant biomass that supports ecological and ecosystem processes. One of the greatest threats to salamanders is loss of headwater-riparian habitat through timber harvest. In this study, we measured larval salamander abundance at five headwater streams with different riparian buffer widths retained following logging. By sampling larval salamanders using leaf litter bags, we assessed the impacts of even-aged timber harvest on aquatic larval salamander abundances, where it was found that larvae are negatively impacted by increased stream sedimentation and a decrease in riparian buffer width. We found that retention of a 9-m buffer was effectively no different than complete removal of all riparian forest, and as such, current regulations to protect headwater streams are ineffectual. Furthermore, no significant differences were observed between the 30 mbuffer treatment and uncut control treatments suggesting that a 30 mor larger riparian buffer may assuage the in-stream effects of riparian timber harvest. Management guidelines for Appalachian forests should be revised to accommodate the biology of plethodontid salamanders.

Petty, J.D. Grossman, G.D. 2009. Giving-up densities and ideal pre-emptive patch use in a predatory benthic stream fish. Freshwater Biology.

Abstract
1. We used observational and experimental field studies together with an individual-based simulation model to demonstrate that behaviours of mottled sculpin (Cottus bairdi) were broadly consistent with the expectations of Giving-Up Density theory and an Ideal Pre-emptive Distribution habitat selection model. 2. Specifically we found that: (i) adult mottled sculpin established territories within patches characterised by significantly higher prey densities and prey renewal rates than patches occupied by juveniles or randomly selected patches; (ii) patches abandoned by adult sculpin possessed significantly lower prey densities than newly occupied patches, although this was not true for juveniles; (iii) the observed giving-up density (GUD) for adult sculpin (i.e. average prey density in patches recently abandoned) increased linearly with increasing fish size up to the average prey density measured in randomly selected patches (i.e. 350 prey items per 0.1 m2) and decreased with increasing sculpin density and (iv) juveniles rapidly shifted their distribution towards the highest quality patches following removal of competitively dominant adult sculpin. 3. These results provide the first evidence of the applicability of GUD theory to a streamdwelling organism, and they elucidate the underlying factors influencing juvenile and adult sculpin habitat selection and movement behaviours. Furthermore, optimal patch use, ideal pre-emptive habitat selection and juvenile ‘floating’ provide behavioural mechanisms linking environmental heterogeneity in the stream benthos to density-dependent regulation of mottled sculpin populations in this system.

Riscassi, A.L., Scanlon, T.M. 2009. Nitrate variability in hydrological flow paths for three mid-Appalachian forested watersheds following a large-scale defoliation. Journal of Geophysical Research, 114: G02009.

Abstract
Nitrate (NO3) leakage from forested watersheds due to disturbance is a well documented but not well understood process that can contribute to the degradation of receiving waters through eutrophication. Several studies have shown that large-scale defoliation and deforestation events in small forested watersheds in the eastern United States cause immediate and dramatic increases in NO3 flux to steams, with large differences in recovery time. Water quality and discharge data collected from 1992 to 2004 following a large-scale gypsy moth defoliation were used to investigate hydrological controls on long-term NO3 leakage from three forested watersheds in Shenandoah National Park, Virginia. During storm events, a conventional two-component hydrograph separation in conjunction with an inverse solution technique was employed to determine the concentrations of NO3 in groundwater and soil water. Following defoliation, groundwater NOJ concentrations declined exponentially with a distinct seasonal pattern. A rank-order relationship between the rate constants associated with the exponential declines in groundwater NO3 concentrations and groundwater recession constants indicates a hydrological control on long-term watershed recovery for these defoliated systems. Comparisons to deforested systems in Hubbard Brook, New Hampshire, and Coweeta, North Carolina, indicate hydrological controls are similarly present. Biogeochemical differences, however, need to be considered to account for the more attenuated recovery observed in defoliated systems. No long-term trend was found in the model-derived soil water NO3 concentrations, which suggests the presence of some form of rate limitation on the transformation of the nitrogen pool introduced during the disturbance and/or reduced nutrient uptake due to tree mortality.

Scott, C. H., M. Cashner, G. D. Grossman, and J. P. Wares. 2009. An awkward introduction: phylegeography of notropis lutipinnis in its 'native' range and the little tennessee river. Ecology of Freshwater Fish, 18: 538-549.

Abstract
We evaluate the putative introduction of the yellowfin shiner, Notropis lutipinnis, in the Little Tennessee river basin. This species has only been noted in the Little Tennessee in the past several decades and appears to be expanding its range, even though there have been many potential historical pathways for dispersal from native drainages in Georgia, South Carolina, and North Carolina. We use a phylogeographic approach, examining sequence data from one mitochondrial and one nuclear locus, to determine the likely source of the population in the Little Tennessee. Our results suggest a complex history and cannot reject the possibility that N. lutipinnis is native to the Little Tennessee. Our data also indicate that particular drainages, including populations in the Altamaha and Flint Rivers, may be subject to local adaptation at the nuclear transferrin locus.

Simon, K., Simon, M., Benfield, E. 2009. Variation in ecosystem function in Appalachian streams along an acidity gradient. The Ecological Society of America, 19(5): 1147-1160

Abstract
Acidification is a widespread phenomenon that damages aquatic systems, and it has been the focus of intensive management efforts. While most management has focused on community structure as an endpoint, ecosystem function is also sensitive to acidification and important in stream health. We examined how a key ecosystem function in streams, leaf breakdown, varied along a gradient of pH resulting from acid deposition, natural conditions, and liming. We also measured how invertebrate and microbial assemblage structure and microbial function were related to altered leaf breakdown rates. Leaf breakdown rates declined more than threefold along a gradient of stream acidity from pH 6.8 to 4.9. The diversity of leaf-shredding invertebrates, bacteria, and fungi showed little response to variation in pH. The abundance of one acid-sensitive caddisfly, Lepidostoma, declined with acidification, and Lepidostoma abundance explained 37% of the variation in leaf breakdown rates among sites. Microbial respiration was suppressed along the acidity gradient, although the pattern was weaker than that for breakdown rate. In short-term laboratory incubations, microbes at acidic and circumneutral sites demonstrated adaptation to ambient pH. The activity of microbial extracellular enzymes was strongly influenced by pH. In particular, the pattern of activity of phosphatase indicated increasing P limitation of microbes with increasing acidification. Our results show that leaf breakdown is a sensitive tool for examining the response of stream function to acidification and also for defining the mechanisms that drive functional response. Future management efforts should focus on key taxa that are particularly sensitive and effective at shredding leaves and also the role of shifting acidity in mediating the availability of phosphorus to microbial films that are important for stream function.

Skyfield, J.P., Grossman, G.D. 2009. Quantifying microhabitat availability: stratified random versus constrained focal-fish methods. Hydrobiologia 624: 235-240.

Abstract
During a study of microhabitat use by gilt darters (Percina evides), we compared two methods for quantifying microhabitat availability in a southern Appalachian stream (USA). The first method used stratified random sampling throughout the site and the second involved taking constrained random measurements within a 2-m radius of the focal fish. Darters were generally over-represented in microhabitats with higher average velocities, greater amounts of erosional substrata, and lower amounts of depositional and large substrata. The two methods generally yielded similar patterns of microhabitat use. Nonetheless, of the seven microhabitat categories in which differential microhabitat use occurred in summer, four were present in both data sets, but three differed between methods. We observed no differences between methods for autumn data. Finally, the standard deviations of the summer-stratified random data set were significantly greater (sign test, P\0.05) than those of the constrained data set. Our results suggest that either method for quantifying microhabitat availability can be used to quantify the general habitat use patterns of this species, but constrained analyses yielded a more restricted view of the total habitat available. Nonetheless, if the fishes range over a site, clearly stratified habitat availability analysis is preferred.

Stodola, K. W., E. T. Linder, D. A. Buehler, K. E. Franzreb, and R. J. Cooper. 2009. Parental care in the multi-brooded black-throated blue warbler. The Conder, 111(3): 497-502.

Abstract
Maximizing reproductive output often entails a trade-off between energy spent on current breeding attempts and that saved for future reproductive opportunities. For species with biparental care, energy spent on the current breeding attempt represents not only a trade-off with future breeding opportunities but also an interaction with the energetic effort of one’s mate. In most songbird species, the female typically invests the most in the early stages of breeding. Consequently, the male’s contribution to provisioning young may free the female from this energetically costly activity and aid her ability to attempt a second brood. We investigated parental provisioning in the Black-throated Blue Warbler (Dendroica caerulescens) to see if males and females altered their provisioning rates with respect to first and second broods. Using parental provisioning rates from 239 nests from three study sites over 6 years, we show that females provisioned young of first broods at a rate lower than that for second broods, while males’ provisioning rate did not differ. Males’ provisioning rate was inversely associated with that of females, with males increasing their provisioning when the number of young in a nest increased while females’ provisioning decreased. Consequently, we believe our results highlight both the trade-off in energy females spend on current and future reproduction and the role of males’ care in helping to maintain reproductive output through increased effort when conditions for feeding are difficult.

Strickland, M.S., Lauber C., Fierer, N, Bradford, M.A. 2009. Testing the functional significance of microbial community composition. Ecology, 90(2): 441-451.

Abstract
A critical assumption underlying terrestrial ecosystem models is that soil microbial communities, when placed in a common environment, will function in an identical manner regardless of the composition of that community. Given high species diversity in microbial communities and the ability of microbes to adapt rapidly to new conditions, this assumption of functional redundancy seems plausible. We test the assumption by comparing litter decomposition rates in experimental microcosms inoculated with distinct microbial communities. We find that rates of carbon dioxide production from litter decomposition were dependent upon the microbial inoculum, with differences in the microbial community alone accounting for substantial (;20%) variation in total carbon mineralized. Communities that shared a common history with a given foliar litter exhibited higher decomposition rates when compared to communities foreign to that habitat. Our results suggest that the implicit assumption in ecosystem models (i.e., microbial communities in the same environment are functionally equivalent) is incorrect. To predict accurately how biogeochemical processes will respond to global change may require consideration of the community composition and/or adaptation of microbial communities to past resource environments.

Strickland, M.S., Osburn, E., Lauber, C., Fierer, N., Bradford, M.A. 2009. Litter quality is in the eye of the beholder: initial decomposition rates as a function of inoculum characteristics. Functional Ecology 23(3) 627-636.

Abstract
1.The chemical composition of plant litter is commonly considered to indicate its quality as a resource for decomposer organisms. Litter quality, defined in this way, has been shown to be a major determinant of litter decomposition rates both within and across terrestrial ecosystems. Notably, the structure of the microbial community that is directly responsible for primary decomposition is rarely considered as an empirical predictor of litter decay rates. 2. Microbial communities are generally assumed to perceive litters of the same chemical composition to be of equivalent resource quality but evidence from field studies suggests that these same communities may adapt to the prevalent litter types at a given site. Here, we tested this assumption by assessing how microbial communities sourced from different forest- and herbaceous-dominated ecosystems perceive the quality of novel, foliar litters derived from a tree (Rhododendron maximum) and from a grass (Panicum virgatum) species. Based on chemical composition, we would expect R. maximum litter to be of lower quality than P. virgatum litter. 3. We used an experimental litter–soil system which employs a ‘common garden’ approach and measured rates of CO2 production across 50 days; higher rates of production were assumed to indicate higher quality (i.e. more easily degradable) litter. 4. We found that communities sourced from habitats under differing plant cover perceived litter quality differently. Those communities sourced from herbaceous habitats perceived the grass litter to be of higher quality than the tree litter, whereas communities from forest habitats decomposed both litter types similarly. Within a litter type, differences in both community composition and nutrient availability of the source habitat were related to decomposition rates. 5. Our results suggest that litter quality cannot necessarily be predicted solely from chemical characteristics; instead the perceived quality is dependent on the quality of past resource inputs a community has experienced and the structure of those microbial communities responsible for the initial stages of litter decomposition.

Swank, W.T., Vose, J.M. 2009. Long-Term Forest Ecosystem Research: A Programmatic View. Journal of Forestry: 355-356

Abstract
Long-term research provides the building blocks of knowledge needed to address natural resource and environmental issues. "Long-term" has frequently been considered to span decades with a time frame that usually encompasses at least one generation of scientists and frequently two or more generations. In the rich history of forest science, the origin of long-term studies can be found in many different forms, ranging from a dedicated lifetime of investigation by a single or small group of scientists on specific topics to large interdisciplinary studies of forest ecosystems comprised of collaborative partnerships between universities, federal and state agencies, and other institutions. Scientific advances in many specific disciplines of forest science (e.g., forest genetics, biometrics, etc.) are well established over time, but interdisciplinary forest ecosystem studies are of more recent origin (20-40 years). The ushering in of the 21 st century coincides with the centennial celebration of the US Forest Service Experimental Forests and Ranges (EFRs). The current network of 81 EFRs has provided a significant core of information on long-term patterns and processes for a diverse array of forest and grassland ecosystems. Lugo et al. (2006) provide an overview of long-term research at EFRs and highlights some of the past, present, and potential future contributions of EFRs to address environmental and natural resource issues. Celebrations commemorating milestones of existence have been initiated at many EFRs along with vignettes that feature select sites and success stories both at the national (USFS 2009) and station level (Southern Research Station 2009). Site-specific activities are also planned; for example, in Nov. 2009 the Coweeta Hydrologic Laboratory in North Carolina will host a Science Symposium celebrating 75 years of research. This event will complement research findings documented for the first 50 years of research at the Laboratory (Swank and Crossley 1988).

Vieilledent, G., B. Courbaud, G. Kunstler, J.-F. Dhôte, and J. S. Clark. 2009. Biases in the estimation of size dependent mortality models: advantages of a semi-parametric approach. Canadian Journal of Forest Research, 39, 1430-1443.

Abstract
Mortality rate is thought to show a U-shape relationship to tree size. This shape could result from a decrease of competition-related mortality as diameter increases, followed by an increase of senescence and disturbance-related mortality for large trees. Modeling mortality rate as a function of diameter is nevertheless difficult, first because this relationship is strongly nonlinear, and second because data can be unbalanced, with few observations for large trees. Parametric functions, which are inflexible and sensitive to the distribution of observations, tend to introduce biases in mortality rate estimates. In this study we use mortality data for Abies alba Mill. and Picea abies (L.) Karst. to demonstrate that mortality rate estimates for extreme diameters were biased when using classical parametric functions. We then propose a semiparametric approach allowing a more flexible relationship between mortality and diameter. We show that the relatively shade-tolerant A.alba has a lower annual mortality rate (2.75%) than P. abies (3.78%) for small trees (DBH <15cm). Picea abies, supposedly more sensitive to bark beetle attacks and windthrows, had a higher mortality rate (up to 0.46%) than A.alba (up to 0.30%) for large trees (DBH =50cm).

Walker, J.T., Vose, J.M., Knoepp, J., Geron, C.D. 2009. Recovery of Nitrogen Pools and Processes in Degraded Riparian Zones in the Southern Appalachians. Journal of Environmental Quality, 38:1391-1399.

Abstract
Establishment of riparian buff ers is an eff ective method for reducing nutrient input to streams. However, the underlying biogeochemical processes are not fully understood. The objective of this 4-yr study was to examine the eff ects of riparian zone restoration on soil N cycling mechanisms in a mountain pasture previously degraded by cattle. Soil inorganic N pools, fl uxes, and transformation mechanisms were compared across the following experimental treatments: (i) a restored area with vegetation regrowth; (ii) a degraded riparian area with simulated eff ects of continued grazing by compaction, vegetation removal, and nutrient addition (+N); and (iii) a degraded riparian area with simulated compaction and vegetation removal only (-N). Soil solution NO3– concentrations and fl uxes of inorganic N in overland fl ow were >90% lower in the restored treatment relative to the degraded (+N) treatment. Soil solution NO3– concentrations decreased more rapidly in the restored treatment relative to the degraded (-N) following cattle (Bos taurus) exclusion. Mineralization and nitrifi cation rates in the restored treatment were similar to the degraded (-N) treatment and, on average, 75% lower than in the degraded (+N) treatment. Nitrogen trace gas fl uxes indicated that restoration increased the relative importance of denitrifi cation, relative to nitrifi cation, as a pathway by which N is diverted from the receiving stream to the atmosphere. Changes in soil nutrient cycling mechanisms following restoration of the degraded riparian zone were primarily driven by cessation of N inputs. The recovery rate, however, was infl uenced by the rate of vegetation regrowth.

Wallace, J., Eggert, S. 2009. Benthic Invertebrate Fauna, Small Streams. Encyclopedia of Inland Waters, 2: 173-190

Abstract
Small streams (first- through third-order streams) make up >98% of the total number of stream segments and >86% of stream length in many drainage networks. Small streams occur over a wide array of climates, geology, and biomes, which influence temperature, hydrologic regimes, water chemistry, light, substrate, stream permanence, a basin’s terrestrial plant cover, and food base of a given stream. Small streams are generally most abundant in the upper reaches of a basin, but they can also be found throughout the basin and may enter directly into larger rivers. They have maximum interface with the terrestrial environment, and in most temperate and tropical climates they may receive large inputs of terrestrial, or allochthonous, organic matter (e.g., leaves, wood) from the surrounding plant communities. In locations with open canopies such as grasslands and deserts, autochthonous or primary production in the form of algae, or higher aquatic plants, may serve as the main food base. Hence, headwater streams display a diverse fauna, which is often adapted to physical, chemical, and biotic conditions of the region.

Wallace, J.B. and S.L. Eggert. 2009. Terrestrial and longitudinal linkages of headwater streams. In Canaan Valley and its Environs: A Landscape Heritage Celebration. Canaan Valley Institute, Davis, West Virginia. http://www.canaanvi.org/canaanvi_web/uploa

Abstract
Headwater streams are important habitats for aquatic invertebrates, amphibians and fish. Within forested regions, headwater streams combined with adjacent forests and riparian zones are sites of organic matter deposition, storage, processing, and subsequent transport. In most streams draining deciduous forest, this organic matter from the surrounding forest provides the major fuel for the ecosystem. In addition to serving as habitat, these streams perform many valuable ecosystem services such as nutrient retention and transformation, hydraulic retention, sediment retention, thermal refuges, moderation of thermal regimes, and are important sites of secondary production for higher animals, including fish and birds. Unfortunately, headwater streams are being subjected to a diverse array of insults, which includes dams, urbanization (including residential, commercial and industrial use), agriculture, forestry, and mining interests, from man without fully considering the long-term consequences of our actions. Ecologists need to promote the importance of headwater streams as well devote more research to examining entire stream networks rather than individual, or simple longitudinal linkages along one system.

Walls, S.C. 2009. The role of climate in the dynamics of a hybrid zone in Appalachian salamanders. Global Change Biology, 15: 1903-1910.

Abstract
I examined the potential influence of climate change on the dynamics of a previously studied hybrid zone between a pair of terrestrial salamanders at the Coweeta Hydrologic Laboratory, U.S. Forest Service, in the Nantahala Mountains of North Carolina, USA. A 16-year study led by Nelson G. Hairston, Sr. revealed that Plethodon teyahalee and Plethodon shermani hybridized at intermediate elevations, forming a cline between ‘pure’ parental P. teyahalee at lower elevations and ‘pure’ parental P. shermani at higher elevations. From 1974 to 1990 the proportion of salamanders at the higher elevation scored as ‘pure’ P. shermani declined significantly, indicating that the hybrid zone was spreading upward. To date there have been no rigorous tests of hypotheses for the movement of this hybrid zone. Using temperature and precipitation data from Coweeta, I re-analyzed Hairston’s data to examine whether the observed elevational shift was correlated with variation in either air temperature or precipitation from the same time period. For temperature, my analysis tracked the results of the original study: the proportion of ‘pure’ P. shermani at the higher elevation declined significantly with increasing mean annual temperature, whereas the proportion of ‘pure’ P. teyahalee at lower elevations did not. There was no discernable relationship between proportions of ‘pure’ individuals of either species with variation in precipitation. From 1974 to 1990, low-elevation air temperatures at the Coweeta Laboratory ranged from annual means of 11.8 to 14.2 1C, compared with a 55-year average (1936–1990) of 12.6 1C. My re-analyses indicate that the upward spread of the hybrid zone is correlated with increasing air temperatures, but not precipitation, and provide an empirical test of a hypothesis for one factor that may have influenced this movement. My results aid in understanding the potential impact that climate change may have on the ecology and evolution of terrestrial salamanders in montane regions.

Walters, D.M., Roy, A.H., Leigh, D.S. 2009. Environmental indicators of macroinvertebrate and fish assemblage integrity in urbanizing watersheds. Ecological Indicators, 9: 1222-12333

Abstract
Urbanization compromises the biotic integrity and health of streams, and indicators of integrity loss are needed to improve assessment programs and identify mechanisms of urban effects. We investigated linkages between landscapes and assemblages in 31 wadeable Piedmont streams in the Etowah River basin in northern Georgia (USA). Our objectives were to identify the indicators of macroinvertebrate and fish integrity from a large set of best land cover (n = 45), geomorphology (n = 115), and water quality (n = 12) variables, and to evaluate the potential for variables measured with minimal cost and effort to effectively predict biotic integrity. Macroinvertebrate descriptors were better predicted by land cover whereas fish descriptors were better predicted by geomorphology. Water quality variables demonstrated moderate levels of predictive power for biotic descriptors. Macroinvertebrate descriptors were best predicted by urban cover (-), conductivity (-), fines in riffles (-), and local relief (+). Fish descriptors were best predicted by embeddedness (-), turbidity (-), slope (+), and forest cover (+). We used multiple linear regression modeling to predict descriptors using three independent variable sets that varied in difficulty of data collection. ‘‘Full’’ models included a full range of geomorphic, water quality and landscape variables regardless of the intensity of data collection efforts. ‘‘Reduced’’ models included GIS-derived variables describing catchment morphometry and land use as well as variables easily collected in the field with minimal cost and effort. ‘‘Simple’’ models only included GIS-derived variables. Full models explained 63–81% of the variation among descriptors, indicating strong relationships between landscape properties and biotic assemblages across our sites. Reduced and simple models were weaker, explaining 48–79% and 42–79%, respectively, of the variance among descriptors. Considering the difference in predictive power among these model sets, we recommend a tiered approach to variable selection and model development depending upon management goals. GIS variables are simple and inexpensive to collect, and a GIS-based modeling approach would be appropriate for goals such as site screening (e.g., identification of reference streams). As management goals become more complex (e.g., long-term monitoring programs), additional, easily collected field variables (e.g., embeddedness) should be included. Finally, labor-intensive variables (e.g., nutrients and fines in sediments) could be added to meet complex management goals such as restoration of impaired streams or mechanistic studies of land use effects on stream ecosystems.

Warren, R.J. 2009. An experimental test of well-described vegetation patterns across slope aspects using woodland herb transplants and manipulated abiotic drivers. New Phytologist, 185: 1038-1049

Abstract
• The ubiquitous transition of plant communities across slope aspects is a welldescribed, but rarely tested, ecological dynamic. Aspect position is often used as a proxy for microclimate changes in moisture, light and temperature, but these abiotic drivers are seldom decoupled and very rarely manipulated across slope aspects. • To investigate the mechanisms and demographic stages driving the observed distribution patterns of two woodland herbs in the southeastern USA, seeds and adults were transplanted across north- and south-facing slopes, and moisture and light were experimentally manipulated. • Stage- and species-specific abiotic responses resulted in similar landscape-level patterning for Hexastylis arifolia and Hepatica nobilis, but the underlying abiotic drivers were unique. Adult rather than seed survival best explained the natural distributions across slope aspects, and Hexastylis arifolia was limited by higher temperature, whereas Hepatica nobilis was limited by lower soil moisture. • The stage- and species-specific responses indicated that the use of slope aspect to explain plant distributions not only obfuscates explanatory mechanisms, but probably undermines the portability of results. As abiotic drivers, not topographical proxies, are projected to shift with global climate change, distribution research requires direct abiotic data in association with key demographic stages rather than topographical proxies.

Webster, J., Newbold, J., Thomas, S., Valett, H., Mulholland, P. 2009. Nutrient Uptake and Mineralization during Leaf Decay in Streams – a Model Simulation. International Review of Hydrobiology, 97(4): 372-390

Abstract
We developed a stoichiometrically explicit computer model to examine how heterotrophic uptake of nutrients and microbial mineralization occurring during the decay of leaves in streams may be important in modifying nutrient concentrations. The simulations showed that microbial uptake can substantially decrease stream nutrient concentrations during the initial phases of decomposition, while mineralization may produce increases in concentrations during later stages of decomposition. The simulations also showed that initial nutrient content of the leaves can affect the stream nutrient concentration dynamics and determine whether nitrogen or phosphorus is the limiting nutrient. Finally, the simulations suggest a net retention (uptake > mineralization) of nutrients in headwater streams, which is balanced by export of particulate organic nutrients to downstream reaches. Published studies support the conclusion that uptake can substantially change stream nutrient concentrations. On the other hand, there is little published evidence that mineralization also affects nutrient concentrations. Also, there is little information on direct microbial utilization of nutrients contained in the decaying leaves themselves. Our results suggest several directions for research that will improve our understanding of the complex relationship between leaf decay and nutrient dynamics in streams.

Wenger, S.J., A.H. Roy, C.R. Jackson, E.S. Bernhardt, T.L. Carter, S. Filoso, C.A. Gibson, N.B. Grimm, W.C. Hession, S.S. Kaushal, E. Marti, J.L. Meyer, M.A. Palmer, M.J. Paul, A.H. Purcell, A. Ramirez, A.D. Rosemond, K.A. Schofield, T.R. Schueler, E.B. Sudduth, and C.J. Walsh. 2009. Twenty-six key research questions in urban stream ecology: an assessment of the state of the science. Journal of the North American Benthological Society 28(4):1080-1098.

Abstract
Urban streams have been the focus of much research in recent years, but many questions about the mechanisms driving the urban stream syndrome remain unanswered. Identification of key research questions is an important step toward effective, efficient management of urban streams to meet societal goals. We developed a list of priority research questions by: 1) soliciting input from interested scientists via a listserv and online survey, 2) holding an open discussion on the questions at the Second Symposium on Urbanization and Stream Ecology, and 3) reviewing the literature in the preparation of this paper. We present the resulting list of 26 questions in the context of a review and summary of the present understanding of urban effects on streams. The key questions address major gaps in our understanding of ecosystem structure and function responses (e.g., what are the sublethal impacts of urbanization on biota?), characteristics of urban stream stressors (e.g., can we identify clusters of covarying stressors?), and management strategies (e.g., what are appropriate indicators of ecosystem structure and function to use as management targets?). The identified research needs highlight our limited understanding of mechanisms driving the urban stream syndrome and the variability in characteristics of the effects of urbanization across different biogeoclimatic conditions, stages of development, government policies, and cultural norms. We discuss how to proceed with appropriate management activities given our current incomplete understanding of the urban stream syndrome.

Wurzburger, N. Hendrick, R.L. 2009. Plant litter chemistry and mycorrhizal roots promote a nitrogen feedback in a temperate forest. Journal of Ecology, 97: 528-536

Abstract
1.Relationships between mycorrhizal plants and soil nitrogen (N) have led to the speculation that the chemistry of plant litter and the saprotrophy of mycorrhizal symbionts can function together to closely couple the N cycle between plants and soils. We hypothesized that a tannin-rich, ericoid mycorrhizal (ERM) plant promotes the retention of protein–tannin N in soil, and that this N source is accessible to saprotrophic ERM symbionts and their hosts, but remains less available to co-occurring ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) symbionts and their hosts. 2. We tested this feedback hypothesis in a southern Appalachian forest community composed of two microsites: a hardwood microsite with ECM and AM trees in the overstorey and understorey, and an AM herb layer; and a rhododendron microsite where the understorey and herb layer are replaced by ERM rhododendron. We synthesized 15 N-enriched protein–tannin complexes from leaf litter extracts representing each forest microsite and examined the fate of 15 N in soil volumes 3 months and 1 year after the complexes were placed in the field. 3. Protein–tannin complexes derived from the rhododendron microsite led to a higher retention of 15 N in soil organic matter and a lower recovery in dissolved N pools than those from the hardwood microsite, supporting the hypothesis that rhododendron tannins create stable complexes that increase organic N retention in soils. 4. Rhododendron complexes led to greater 15 N-enrichment in ERM roots than in AM and ECM roots, supporting the hypothesis that rhododendron can better access the N complexed by its own litter tannins than can co-occurring forest trees and plants. Our results suggest that both fungal saprotrophy and a high specific root length contribute to the ability of ERM roots to acquire N from complex organic sources. 5. Synthesis. This study provides evidence of an intricate N feedback where plant litter chemistry influences the cycle of N to maximize N acquisition by the host’s mycorrhizal roots, while hindering N acquisition by mycorrhizal roots of co-occurring plants. Feedback processes such as these have the potential to drive patterns in nitrogen cycling and productivity in many terrestrial ecosystems.

Zehnder, Caralyn B., Kirk W. Stodola, Blake L. Joyce, David Egetter, Robert J. Cooper, and Mark D. Hunter. 2009. Elevational and Seasonal Variation in the Foliar Quality and Arthrood Community of Acer pensyvanicum. Environmental Entomology. 38(4): 1161-67.

Abstract
Elevational gradients provide natural experiments for examining how variation in abiotic forces such as nutrient mineralization rates, risk of photodamge, temperature, and precipitation inßuence plantÐinsect interactions. At the Coweeta LTER site in the Southern Appalachian Mountains, we examined spatial and temporal variation in striped maple, Acer pensylvanicum, foliar quality and associated patterns in the arthropod community. Variation in herbivore densities was associated more strongly with seasonal variation in plant quality than with spatial variation in quality among three sampling sites. Leaf chewer, but not phloem feeder or arthropod predator, densities increased with elevation. Foliar quality, by our measures, decreased throughout the growing season, with decreases in nitrogen concentrations and increases in lignin concentrations. Foliar quality varied among the three sites but not systematically along the elevational gradient. We conclude that, in this system, temporal heterogeneity in plant quality is likely to be more important to insect herbivores than is spatial heterogeneity and that other factors, such as the abiotic environment and natural enemies, likely have substantial effects on herbivore density

Ball, B. A., M. D. Hunter, J. S. Kominoski, C. M. Swan, and M. A. Bradford. 2008. Consequences of non-random species loss on decomposition dynamics: Evidence for additive and non-additive effects. Journal of Ecology 96:303-313.

Abstract
To examine potential impacts of non-random species loss on ecosystems, we studied additive and non-additive effects of litter mixing on decomposition. A full-factorial litterbag experiment was conducted using four deciduous leaf species, from which mass loss and nitrogen content were measured. Data were analysed using a statistical approach that first looks for additive identity effects based on the presence or absence of species and then significant species interactions occurring beyond those. It partitions non-additive effects into those caused by richness and/or composition.

Barton, C.D., Andrews, D.M., Kolka, R.A. 2008. Evaluating Hydroperiod Response in Restored Carolina Bay Wetlands Using Soil Physicochemical Properties. Restoration Ecology 16(4) 668-677.

Abstract
Carolina bays are shallow depression wetlands found in the southeastern United States that have been severely altered by human activity. The need to restore these complex and diverse systems is well established, but our limited understanding of wetland hydrologic processes in these systems hinders our ability to assess the effectiveness of bay restoration efforts. Carolina bays exhibit a wide range of moisture regimes from seasonally saturated to semipermanently inundated. Differing physicochemical properties of soils within bay interiors may control bay hydrology. However, previous efforts to establish relationships between soil characteristics and bay hydrology have been inconclusive. An assessment of soil and hydroperiod was initiated in 16 bays designated to be restored and 6 bays that were not restored (reference). Soil morphology was described, and permanent monitoring wells were installed at each site. Multiple regression analysis was used to determine relationships between the soil physicochemical characteristics and the bay hydroperiod for restored and reference bays in both pre- and postrestoration periods. A significant relationship (r2 = 0.75, p = 0.02) between prerestoration hydroperiod and clay content in the argillic horizon (Bt) of the reference bays was observed. This relationship was then used to evaluate hydroperiod change in the restored bays from the postrestoration period. The relationship accurately identified sites that exhibited high prerestoration hydroperiods and did not need hydrologic restoration (n = 4) and effectively showed sites that exhibited substantial increases in hydroperiod due to the restoration activities (n = 7).

Beckage, B., B.D. Kloeppel, J.A. Yeakley, S.F. Taylor, and D.C. Coleman. 2008. Differential effects of understory and overstory gaps on tree regeneration. Journal of the Torrey Botanical Society. 135(1):1-11.

Abstract
Gaps in the forest canopy can increase the diversity of tree regeneration. Understory shrubs also compete with tree seedlings for limited resources and may depress tree recruitment. We compared effects of shrub removal and canopy windthrow gaps on seedling recruitment and understory resource levels.

Bolstad, P.V., and T.L. Gragson. 2008. Resource abundance constraints on the early post-contact Cherokee population. Journal of Archeological Science 35:563-576.

Abstract
We present the combination of an analysis of resource demand by the early post-contact (1721) Cherokee population with spatially explicit estimates of production for five key resources: architectural land, agricultural land, firewood, hard mast, and white-tailed deer (Odocoileus virginianus). We combine a recent synthesis of village location and population, a map of recognized Cherokee territory, digital terrain data, estimates of per capita demand, and productive capacity for each resource. Average, high, and low demands were estimated for each resource and assigned based on a weighted function of terrain and distance from each village. We conclude that Cherokee demands for architectural and agricultural land, hard mast, and fuelwood were easily met within a short proximity to each town under all combinations of production and demand. These resources were likely not limiting, and were satisfied for the entire Cherokee population by less than 1% of the entire recognized Cherokee territory in 1721. These resources likely exceeded demand even when sources were restricted to the convex hull of the Cherokee territory, or to near stream, flat regions. Deer resources were likely harvested over a much larger area and to a much greater extent. Our best estimate of deer resource demand was 32% of annual sustainable production in the Cherokee territory, with from 16 to 48% of estimated sustainable production harvested for low and high demand estimates, respectively. Our estimates vary in response to uncertainties in deer production, harvest proportion, deer density, and sustainable harvest rates. Deer demand was substantially higher under all combinations of conditions than that available within the convex hull of Cherokee villages, indicating significant travel was needed to furnish deer requirements. Spatially explicit models that consider terrain- and distance-related tradeoffs suggest that Cherokee demand for deer drove harvest over areas consisting of over half the recognized Cherokee territory.

Bradford, M.A., T. Gancos, and C.J. Frost. 2008. Slow-cycle effects of foliear herbivory alter the nitrogen acquistion and population size of Collembola. Soil Biology and Biochemistry 40: 1253-1258

Abstract
In terrestrial systems there is a close relationship between litter quality and the activity and abundance of decomposers. Therefore, the potential exists for aboveground, herbivore-induced changes in foliar chemistry to affect soil decomposer fauna. These herbivore-induced changes in chemistry may persist across growing seasons. While the impacts of such slow-cycle, ‘legacy’ effects of foliar herbivory have some support aboveground, such impacts have not been evaluated for soil invertebrates. Here, we investigate legacy effects on Collembola population structure and nitrogen acquisition. We collected foliar material (greenfall) from trees that had, in the preceding season, been exposed to insect herbivory by leaf-chewing Lepidoptera.

Burcher, C.L., M.E. McTammany, E.F. Benfield, and G.S. Helfman. 2008. Fish assemblages responses to forest cover.  Environmental Management. 41: 336-346.

Abstract
We investigated whether fish assemblage structure in southern Appalachian streams differed with historical and contemporary forest cover. We compared fish assemblages in 2nd–4th order streams draining watersheds that had increased forest cover between 1950 and 1993 (i.e., reforesting watersheds). We sampled fish in 50 m reaches during August 2001 and calculated catch-per-unit-effort (CPUE) by taxonomic, distributional, trophic, reproductive, and thermal metrics. We assigned streams to reforestation categories based on cluster analysis of years 1950 and 1993 near-stream forest cover. The relationship between forest cover and assemblage structure was assessed using analysis of variance to identify differences in fish CPUE in five forest cover categories.

Chamblee, J.F., Dehring, C.A., Depken, C.A. 2008. Watershed development restrictions and land prices: Empirical evidence from southern Appalachia. Regional Science and Urban Economics. 39: 287-296

Abstract
The State of North Carolina's Water Supply Watershed Protection Act of 1989 required local governments to adopt land use measures in watersheds to protect the water supply emanating from the watersheds. We examine vacant land prices in the Ivy River watershed of Buncombe County, NC, at the time such regulation took effect. Our results suggest that costs of watershed development restrictions are borne primarily by those vacant land owners in the watershed for whom the development restrictions make land subdivision infeasible.We find benefits accruing to land owners on the public water supply or who are adjacent to creeks.

Chung, N., Suberkropp, K. 2008. Influence of shredder feeding and nutrients on fungal activity and community structure in headwater streams. Fundamental and Applied Limnology, 173(1): 35-46.

Abstract
In stream detrital food webs, interactions occur between aquatic hyphomycetes associated with decomposing leaves and shredders consuming those leaves. However, few studies have examined how the feeding activity of shredders affects aquatic hyphomycetes. We examined the effect of shredder feeding on aquatic hyphomycete communities associated with submerged leaves in two southern Appalachian headwater streams in Coweeta Hydrologic Laboratory, North Carolina, USA. Coarse (allowing shredder access) and fi ne (preventing shredder access) mesh litter bags containing red maple (Acer rubrum) leaves were placed in the treatment stream (C54) which was enriched with nitrogen (N) and phosphorus (P), and in the reference stream (C53) and were retrieved monthly. Both shredder feeding and nutrient enrichment enhanced breakdown rates. The breakdown rates of leaves in coarse mesh bags in the reference stream (k = 0.0275) and fi ne mesh bags in the nutrient enriched stream (k = 0.0272) were not signifi cantly different, suggesting that the higher fungal activity stimulated by nutrient enrichment could increase the relative contribution of fungi to leaf breakdown to the level similar to that of shredders in the reference stream. Macroinvertebrate abundance and biomass were higher in the litter bags submerged in the treatment stream. Fungal sporulation rates and biomass were higher in the treatment stream than in the reference stream, but neither fungal biomass nor sporulation rate was affected by shredder feeding in either stream. The enrichment with N and P altered fungal community composition more than shredder feeding. Species richness was higher in the nutrient enriched stream than in the reference stream, and fungal assemblages from fi ne and coarse mesh bag treatments within a stream were more similar to each other than the fungal assemblages from the same mesh bag treatments but from different streams.

Coleman, D.C. 2008. From peds to paradoxes: Linkages between soil biota and their influences on ecological processes. Soil Biology & Biochemistry. 40: 271-289.

Abstract
Soils and their biota have been studied by a variety of observational and experimental methods that have allowed biologists to infer their structural and functional interactions. Viewing progress made over the last 10 years, it is apparent that an increasing diversity of analytical and chemical methods are providing much more detailed information about feeding preferences and niche overlaps of speciose groups such as oribatid mites. Other topics in which considerable progress has been made include new advances in knowledge of root and mycorrhiza production and turnover and their impacts on soil ecosystems; soil biota, exudations and secretions and soil aggregation phenomena; the biology of invasive species in soils;soil biodiversity, legacies and linkages to soil processes; and soil biodiversity and ecosystem functional responses. Throughout the review, the author suggests ways for new progress to be made in future research.

Dietze, M.C., Clark, J.S. 2008. Changing the Gap Dynamics Paradigm: Vegetative Regeneration Control on Forest Response to Disturbance. Ecological Monographs 78(3) 331-347.

Abstract
Understanding the manner in which changes in disturbance regimes will affect forest biodiversity is an important goal of global change research. Prevailing theories of recruitment after disturbance center on the role of pioneer species; predictions of forest biodiversity focus almost exclusively on dispersal and shade tolerance while vegetative reproduction is virtually omitted from models and serious discussions of the topic. However, the persistence of live damaged trees increases understory shade, generates fine-scale environmental heterogeneity, and moderates ecosystem responses to damage, while the sprouting of damaged trees offers a shortcut to reestablishment of the canopy. While a number of studies document snapshots of post-disturbance vegetative reproduction, we lack an understanding of the underlying demographic processes needed in order to both comprehend and predict observed patterns. In this study we quantify the abundance, competitive ability, and interspecific variability of vegetative reproduction in 18 replicated experimental gaps in the southern Appalachians and Carolina Piedmont, USA, in order to assess the potential role of sprouting in driving gap dynamics. Annual rates of damaged adult survival, sprout initiation, growth, and mortality were monitored over four years and compared to the performance of gap-regenerating saplings. Recruitment from sprouts was found to constitute 26–87% of early gap regeneration and forms the dominant pathway of regeneration for some species. Sprouts from recently damaged trees also grow significantly faster than the saplings with which they compete. For all measured demographic rates (damaged tree survival, sprout initiation, number, growth, and survival) differences among species are large and consistent across sites, suggesting that vegetative reproduction is an important and non-neutral process in shaping community composition. Sprouting ability does not correlate strongly with other life-history trade-offs, thus sprouting potentially provides an alternate trait axis in promoting diversity.

Dietze, M.C., Wolosin, M.S., Clark, J.S. 2008. Capturing diversity and interspecific variability in allometries: A hierarchical approach. Forest Ecology and Management 256: 1939-1948

Abstract
There is growing recognition of the role of mechanistic scaling laws in shaping ecological pattern and process. While such theoretical relationships explain much of the variation across large scales, at any particular scale there is important residual variation that is left unexplained among species, among individuals within a species, and within individuals themselves. Key questions remain on what explains this variability and how we can apply this information in practice, in particular to produce estimates in high-diversity systems with many rare and under-sampled species. We apply hierarchical Bayes statistical techniques to data on crown geometry from diverse temperate forests in order to simultaneously model the differences within and among species. We find that tree height, canopy depth, and canopy radius are affected by both successional stage and wood mechanical strength, while tree height conforms to the predicted 2/3 power relationship. Furthermore, we show that hierarchical modeling allows us to constrain the allometries of rare species much more than traditional methods. Finally, crown radius was shown to vary substantially more within individuals than among individuals or species, suggesting that the capacity for local light foraging and crown plasticity exerts the dominant control on tree crowns.

Elliott, K.J., and W.T. Swank. 2008. Long-term changes in forest composition and diversity following early logging (1919-1923) and the decline of American chestnut (Castanea dentate). Plant Ecology. 197: 155-172.

Abstract
Chestnut blight fungus (Endothia parasitica [Murr.] P.J. And. & H.W. And.)) is a classic example of an invasive species, which severely damaged populations of its host, Castanea dentata, and had widespread and long-term impacts on eastern North American forests. Concurrently, forests were further disturbed by lumbering, which was common across the region from the mid 1800s to the early 1900s. In 1926, local infestations of chestnut blight were reported in the Coweeta Basin, Southern Appalachian Mountains of North Carolina. We used permanent plot inventories of the Basin (first sampled in 1934 and twice afterward in 1969–72 and 1988–93) to describe the distribution of species along a complex environmental gradient. Specifically, we asked: How does vegetation change over approximately 60 years following logging and the demise of C. dentata? Does the association between vegetation and environment determine the pattern of species distributions through time? Which species replaced C. dentate across this complex environmental gradient? We used nonmetric multidimensional scaling ordination and multiresponse permutation procedure for the analyses of the inventory periods. In 1934, C. dentata was the most important species in the Coweeta Basin. It was present in 98% of the plots and contributed 22% of the total density and 36% of the total basal area. Diversity increased significantly over time and was attributed to an increase in evenness of species distribution. The canopy dominant, C. dentata, was replaced by more than one species across the environmental gradient. Importance values of Quercus prinus, Acer rubrum, Cornus florida, Tsuga canadensis, and Oxydendrum arboreum increased by 2–5% across the basin following the decline of C. dentata. Tsuga canadensis increased in abundance and distribution, especially near streams across elevations. Liriodendron tulipifera replaced C. dentate in moist coves, which have low terrain shape and high organic matter content. In contrast, Q. prinus and A. rubrum were ubiquitous, much like C. dentate before the chestnut blight becoming dominant or co-dominant species across all environmental conditions.

Elliott, K.J., J.M. Vose, J.D. Knoepp,D.W. Johnson, W.t. Swank,and W. Jackson. 2008. Simulated effects of sulfur deposition on nutrient cycling in class I wilderness areas. Journal of Environmental Quality. 37: 1419-1431.

Abstract
We predicted the effects of sulfate (SO4) deposition on wilderness areas designated as Class I air quality areas in western North Carolina using a nutrient cycling model (NuCM). We used three S deposition simulations: current, 50% decrease, and 100% increase. We measured vegetation, forest floor, and root biomass and collected soil, soil solution, and stream water samples for chemical analyses. We used the closest climate stations and atmospheric deposition stations to parameterize NuCM. The areas were: Joyce Kilmer (JK), Shining Rock (SR), and Linville Gorge (LG)

Ford, C.R., R.J. Mitchell, and R.O. Teskey. 2008. Water table depth affects productivity, water use, and the reponse to nitrogen addition in a savanna system. Canadian Journal of Forest Research. 38: 2118-2127.

Abstract
We investigated annual aboveground net primary productivity (ANPP) and transpiration (E) of the dominant plant life forms, longleaf pine (Pinus palustris Mill.) trees and wiregrass (Aristida stricta Michx.), in a fire-maintained savanna. Experimental plots spanned a natural hydrologic gradient (xeric and mesic site types) mediated by soil moisture () and water table depth (WTD), and received additions of either 0 or 100 kg Nha–1year–1.

Fraterrigo, J. M. and J. A. Rusak. 2008. Disturbance-driven changes in the variability of ecological patterns and processes. Ecology Letters 11:756-770

Abstract
Understanding how disturbance shapes the dynamics of ecological systems is of fundamental importance in ecology. One emerging approach to revealing and appreciating disturbance effects involves examining disturbance-driven changes in the variability of ecological responses. Variability is rarely employed as a response variable to assess the influence of disturbance, but recent studies indicate that it can be an extremely sensitive metric, capturing differences obscured by averaging and conveying important ecological information about underlying causal processes. In this paper, we present a conceptual model to understand and predict the effects of disturbance on variability. The model estimates qualitative changes in variability by considering disturbance extent, frequency and intensity, as well as ecosystem recovery, and thereby captures not only the immediate effects of disturbance but also those that arise over time due to the biotic response to an event. We evaluate how well the model performs by comparing predictions with empirical results from studies examining a wide variety of disturbances and ecosystems, and discuss factors that may modify or even confound predictions. We include a concise guide to characterizing and detecting changes in variability, highlighting the most common and easily applied methods and conclude by describing several future directions for research. By considering variability as a response to disturbance, we gain another metric of fundamental system behaviour, an improved ability to identify organizing features of ecosystems and a better understanding of the predictability of disturbance-driven change – all critical aspects of assessing ecosystem response to disturbance.

Frost, C. J., and M.D. Hunter. 2008. Herbivore-induced shifts in carbon and nitrogen allocation in red oak seedlings. New Phytologist. 178(4): 835-845.

Abstract
A dual-isotope, microcosm experiment was conducted with Quercus rubra (red oak) seedlings to test the hypothesis that foliar herbivory would increase belowground carbon allocation (BCA), carbon (C) rhizodeposition and nitrogen (N) uptake. Plant BCA links soil ecosystems to aboveground processes and can be affected by insect herbivores, though the extent of herbivore influences on BCA is not well understood in woody plants.

Gardiner, N., Sutherland, A. B., Bixby, R. J., Scott, M. C., Meyer, J. L, Helfman, G. S., Benfield, E. F., Pringle, C. M., Bolstad, C. M., and D. N. Wear. 2008. Linking stream and landscape trajectories in the southern Appalachians. Environmental Monitoring and Assessment. 156(1-4):17-36.

Abstract
A proactive sampling strategy was designed and implemented in 2000 to document changes in streams whose catchment land uses were predicted to change over the next two decades due to increased building density. Diatoms, macroinvertebrates, fishes, suspended sediment, dissolved solids, and bed composition were measured at two reference sites and six sites where a socioeconomic model suggested new building construction would influence stream ecosystems in the future; we label these “hazard sites.” The six hazard sites were located in catchments with forested and agricultural land use histories. Diatoms were species-poor at reference sites, where riparian forest cover was significantly higher than all other sites. Cluster analysis, ishart’s distance function, non-metric multidimensional scaling, indicator species analysis, and t-tests show that macroinvertebrate assemblages, fish assemblages, in situ physical measures, and catchment land use and land cover were different between streams whose catchments were mostly forested, relative to those with agricultural land use histories and varying levels of current and predicted development.

Gulis, V., Suberkropp, K., Rosemond, A. 2008. Comparison of Fungal Activities on Wood and Leaf Litter in Unaltered and Nutrient-Enriched Headwater Streams. Applied and Environmental Microbiology. 74(4):1094-1101

Abstract
Fungi are the dominant organisms decomposing leaf litter in streams and mediating energy transfer to other trophic levels. However, less is known about their role in decomposing submerged wood. This study provides the first estimates of fungal production on wood and compares the importance of fungi in the decomposition of submerged wood versus that of leaves at the ecosystem scale. We determined fungal biomass (ergosterol) and activity associated with randomly collected small wood (<40 mm diameter) and leaves in two southern Appalachian streams (reference and nutrient enriched) over an annual cycle. Fungal production (from rates of radiolabeled acetate incorporation into ergosterol) and microbial respiration on wood (per gram of detrital C) were about an order of magnitude lower than those on leaves. Microbial activity (per gram of C) was significantly higher in the nutrient-enriched stream. Despite a standing crop of wood two to three times higher than that of leaves in both streams, fungal production on an areal basis was lower on wood than on leaves (4.3 and 15.8 g C m 2 year 1 in the reference stream; 5.5 and 33.1 g C m 2 year 1 in the enriched stream). However, since the annual input of wood was five times lower than that of leaves, the proportion of organic matter input directly assimilated by fungi was comparable for these substrates (15.4 [wood] and 11.3% [leaves] in the reference stream; 20.0 [wood] and 20.2% [leaves] in the enriched stream). Despite a significantly lower fungal activity on wood than on leaves (per gram of detrital C), fungi can be equally important in processing both leaves and wood in streams.

Henry, B.E., Grossman, G.D. 2008. Microhabitat use by blackbanded (Percina nigrofasciata), turquoise (Etheostoma inscriptum), and tessellated (E. olmstedi) darters during drought in a Georgia piedmont stream. Environ Biol Fish. 83: 171-182

Abstract
We used underwater observations to quantify microhabitat use for blackbanded, Percina nigrofaciata, turquoise, Etheostoma inscriptum, and tessellated, E.olmsteadi, darters in a 116 m reach of a Piedmont stream during 2001–2002. The sampling period and the previous 12 months were the first and second driest years on record, respectively. Spring 2002 had the greatest amount of available habitat, and principal component analysis indicated that only one of three species pairs displayed significant differences in microhabitat use during this season. Conversely, in fall 2001 (intermediate microhabitat availability), all three species used significantly different microhabitats. In general, turquoise darters used areas with greater amounts of erosional substrata, tessellated darters occurred over more depositional substrata, and blackbanded darters utilized intermediate microhabitats. During fall 2001, large blackbanded darters (?55 mm SL) occupied faster microhabitats with more erosional substrata, and used a greater variety of depths than smaller conspecifics (40–55 mm). In fall 2001, large turquoise darters (?40 mm) used deeper microhabitats with higher velocities and more erosional substrata than smaller individuals, whereas the opposite was true (?50 mm in faster, more erosional, than >50 mm) in fall 2002. In general, darters did not occur in microhabitats with significantly higher invertebrate abundances, however both blackbanded and tessellated darters occupied microhabitats with higher percentages of Diptera in a single season. The inconsistent responses of darters to microhabitat prey abundance may have been influenced by extreme drought conditions.

Ibanez, I., Clark, J.S., Dietze, M.C. 2008. Evaluating the Sources of Potential Migrant Species: Implications Under Climate Change. Ecological Applications, 18(7): 1664-1678.

Abstract
As changes in climate become more apparent, ecologists face the challenge of predicting species responses to the new conditions. Most forecasts are based on climate envelopes (CE), correlative approaches that project future distributions on the basis of the current climate often assuming some dispersal lag. One major caveat with this approach is that it ignores the complexity of factors other than climate that contribute to a species’ distributional range. To overcome this limitation and to complement predictions based on CE modeling we carried out a transplant experiment of resident and potential-migrant species. Tree seedlings of 18 species were planted side by side from 2001 to 2004 at several locations in the Southern Appalachians and in the North Carolina Piedmont (USA). Growing seedlings under a large array of environmental conditions, including those forecasted for the next decades, allowed us to model seedling survival as a function of variables characteristic of each site, and from here we were able to make predictions on future seedling recruitment. In general, almost all species showed decreased survival in plots and years with lower soil moisture, including both residents and potential migrants, and in both locations, the Southern Appalachians and the Piedmont. The detrimental effects that anticipated arid conditions could have on seedling recruitment contradict some of the projections made by CE modeling, where many of the species tested are expected to increase in abundance or to expand their ranges. These results point out the importance of evaluating the potential sources of migrant species when modeling vegetation response to climate change, and considering that species adapted to the new climate and the local conditions may not be available in the surrounding regions.

Jaffe, R., McKnight, D., Maie, N., Cory, R., McDowell, W., Campbell, J. 2008. Spatial and temporal variations in DOM composition in ecosystems: The importance of long-term monitoring of optical properties. Journal of Geophysical Research, 113(G4):G04032

Abstract
Source, transformation, and preservation mechanisms of dissolved organic matter (DOM) remain elemental questions in contemporary marine and aquatic sciences and represent a missing link in models of global elemental cycles. Although the chemical character of DOM is central to its fate in the global carbon cycle, DOM characterizations in long-term ecological research programs are rarely performed. We analyzed the variability in the quality of 134 DOM samples collected from 12 Long Term Ecological Research stations by quantification of organic carbon and nitrogen concentration in addition to analysis of UV-visible absorbance and fluorescence spectra. The fluorescence spectra were further characterized by parallel factor analysis. There was a large range in both concentration and quality of the DOM, with the dissolved organic carbon (DOC) concentration ranging from less than 1 mgC/L to over 30 mgC/L. The ranges of specific UV absorbance and fluorescence parameters suggested significant variations in DOM composition within a specific study area, on both spatial and temporal scales. There was no correlation between DOC concentration and any DOM quality parameter, illustrating that comparing across biomes, large variations in DOM quality are not necessarily associated with corresponding large ranges in DOC concentrations. The data presented here emphasize that optical properties of DOM can be highly variable and controlled by different physical (e.g., hydrology), chemical (e.g., photoreactivity/redox conditions), and biological (e.g., primary productivity) processes, and as such can have important ecological consequences. This study demonstrates that relatively simple DOM absorbance and/or fluorescence measurements can be incorporated into long-term ecological research and monitoring programs, resulting in advanced understanding of organic matter dynamics in aquatic ecosystems.

Jones, B.C., Kleitch, J.L., Harper, C.A., Buehler, D.A. 2008. Forest and Ecology Management 255: 3580-3588

Abstract
Brood habitat quality and availability may be a limiting factor for ruffed grouse (Bonasa umbellus) populations in the central and southern Appalachians.We measured brood habitat characteristics at forest stand and microhabitat scales in western North Carolina. From 2000 to 2004, we monitored radiotagged females with broods (n = 36) from hatch to 5 weeks post-hatch. We measured habitat characteristics and invertebrates at 186 brood locations and 186 paired, random locations. Brood sites had greater percent herbaceous ground cover, greater percent vertical cover 0–2 m, greater density of midstory stems <11.4 cm DBH, and greater invertebrate density compared with random sites. Seventeen broods survived the 5-week post-hatch period and were available for home range and second order habitat preference analysis. Mean 75% kernel home range was 24.3 ha (+-4.0 S.E.). Top-ranked habitats for relative preference were mixed hardwoods in the 0–5, 6–20, and >80-year age classes, forest roads, and edges of maintained wildlife openings. Broods often were associated with managed stands. From this information, we recommend forest management prescriptions to enhance Appalachian ruffed grouse brood habitat.

Jurgelski, W.M. 2008. Burning Season, Burning Bans: Fire in the Southern Appalachian Mountains, 1750-2000. Appalachian Journal 35(3): 170-217

Kane, E. S., E. F. Betts, A. J. Burgin, H. M. Clilverd, C. L. Crenshaw, J. B. Fellman, I. H. Myers-Smith, J. A. O’Donnell, D. J. Sobota, W. J. Van Verseveld, and J. B. Jones. 2008. Precipitation control over inorganic nitrogen import–export budgets across watersheds: a synthesis of long-term ecological research. Ecohydrology, 1: 105-117.

Abstract
We investigated long-term and seasonal patterns of N imports and exports, as well as patterns following climate perturbations, across biomes using data from 15 watersheds from nine Long-Term Ecological Research (LTER) sites in North America. Mean dissolved inorganic nitrogen (DIN) import–export budgets (N import via precipitation–N export via stream flow) for common years across all watersheds was highly variable, ranging from a net loss of !0Ð17 š 0Ð09 kg N ha!1mo!1 to net retention of 0Ð68 š 0Ð08 kg N ha!1mo!1. The net retention of DIN decreased (smaller import–export budget) with increasing precipitation, as well as with increasing variation in precipitation during the winter, spring, and fall. Averaged across all seasons, net DIN retention decreased as the coefficient of variation (CV) in precipitation increased across all sites (r2 D 0Ð48, p D 0Ð005). This trend was made stronger when the disturbed watersheds were withheld from the analysis (r2 D 0Ð80, p < 0Ð001, n D 11). Thus, DIN exports were either similar to or exceeded imports in the tropical, boreal, and wet coniferous watersheds, whereas imports exceeded exports in temperate deciduous watersheds. In general, forest harvesting, hurricanes, or floods corresponded with periods of increased DIN exports relative to imports. Periods when water throughput within a watershed was likely to be lower (i.e. low snow pack or El Ni˜no years) corresponded with decreased DIN exports relative to imports. These data provide a basis for ranking diverse sites in terms of their ability to retain DIN in the context of changing precipitation regimes likely to occur in the future.

Knoepp, J.D., J.M. Vose, and W.T. Swank. 2008. Nitrogen deposition and cycling across an elevation and vegetation gradient in southern Appalachian forests. International Journal of Environmental Studies. 65(3): 389-408.

Abstract
We studied nitrogen (N) cycling pools and processes across vegetation and elevation gradients in the southern Appalachian Mountains in SE USA. Measurements included bulk deposition input, watershed export, throughfall fluxes, litterfall, soil N pools and processes and soil solution N. N deposition increased with elevation and ranged from 9.5 to 12.4 kg ha-1 yr-1.

Kominoski, J.S., C.M. Pringle, and B.A. Ball. 2008. Invasive woolly adelgid appears to drive seasonal hemlock and carcass inputs to a detritus-based stream. Verhandlungen Internationale Vereinigung für theoretische und angewandte Limnologie 30(1):109-112

Abstract
Here we presented data from a 2-year litter trap study, conducted during the early stages of woolly adelgid infestation and hemlock decline. We assess the contribution of eastern hemlock to direct litterfall and lateral inputs to streams as well as entrainment of woolly adelgid carcasses by leaf packs in a second-order reach of Ball Creek, a headwater stream located at Coweeta Hydrologic Laboratory (Coweeta), Macon County, North Carolina, U.S. (35°00’N; 83°30’W).

Kramer, A.T., J.L Ison, M.V. Ashley, and H.F. Howe. 2008. The paradox of forest fragmentation genetics. Conservation Biology. 22(4): 878-885.

Abstract
Theory predicts widespread loss of genetic diversity from drift and inbreeding in trees subjected to habitat fragmentation, yet empirical support of this theory is scarce. We argue that population genetics theory may be misapplied in light of ecological realities that, when recognized, require scrutiny of underlying evolutionary assumptions.

McTammany, M.E., E.F. Benfield, and J.R. Webster. 2008. Effects of agriculture on wood breakdown and microbial biofilm respiration in southern Appalachian streams. Freshwater Biology. 53: 842-854.

Abstract
We examined wood breakdown and microbial activity on wood substrata in streams with different historical and current agricultural activity in their catchments. We analysed historical (1950) and recent (1998) forested land cover from large areas of the southern Appalachians and categorized streams based on percent forested land cover in these two time periods. Categories included a gradient of current agriculture from forested to heavily agricultural and reforestation from agriculture due to land abandonment. We compared microbial respiration on wood veneer substrata and breakdown of wood veneers among these land-use categories. We also compared temperature, sediment accumulation and nitrogen and phosphorus concentrations.

Mulholland, PJ, AM Helton, GC Poole, RO Hall, SK Hamilton, BJ Peterson, JL Tank, LR Ashkenas, LW Cooper, CN Dahm, WK Dodds, SEG Findlay, SV Gregory, NB Grimm, SL Johnson, WH McDowell, JL Meyer, HM Valett, JR Webster, CP Arango, JJ Beaulieu, MJ Bernot, AJ Burgin, CL Crenshaw, LT Johnson, BR Niederlehner, JM O'Brien, JD Potter, RW Sheibley, DJ Sobota, and SM Thomas. 2008. Stream denitrification across biomes and its response to anthropogenic nitrate loading. Nature 452:202-246.

Abstract
Anthropogenic addition of bioavailable nitrogen to the biosphere increasing and terrestrial ecosystems are becoming increasingly nitrogen-saturated, causing more bioavailable nitrogen to enter groundwater and surface waters. Large-scale nitrogen budgets show that an average of about 20-25 per cent of the nitrogen added to the biosphere is exported from rivers to the ocean or inland basins, indicating that substantial sinks for nitrogen must exist in the landscape. Streams and rivers may themselves be important sinks for bioavailable nitrogen owing to their hydrological connections with terrestrial systems, high rates of biological activity, and streambed sediment environments that favour microbial denitrification. Here we present data from nitrogen stable isotope tracer experiments across 72 streams and 8 regions representing several biomes. We show that total biotic uptake and denitrification of nitrate increase with stream nitrate concentration, but that the efficiency of biotic uptake and denitrification declines as concentration increases, reducing the proportion of in-stream nitrate that is removed from transport. Our data suggest that the total uptake of nitrate is related to ecosystem photosynthesis and that denitrification is related to ecosystem respiration. In addition, we use a stream network model to demonstrate that excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate that is exported to receiving waters and reduces the relative role of small versus large streams as nitrate sinks.

Owens, A.K., Moseley, K.R., McCay, T.S., Castleberry, S.B., Kilgo, J.C., Ford, M.W. 2008. Forest and Ecology Management 256: 2078-2083

Abstract
Coarse woody debris (CWD) has been identified as a key microhabitat component for groups that are moisture and temperature sensitive such as amphibians and reptiles. However, few experimental manipulations have quantitatively assessed amphibian and reptile response to varying CWD volumes within forested environments. We assessed amphibian and reptile response to large-scale, CWD manipulation within managed loblolly pine stands in the southeastern Coastal Plain of the United States from 1998 to 2005. Our study consisted of two treatment phases: Phase I treatments included downed CWD removal (removal of all downed CWD), all CWD removal (removal of all downed and standing CWD), pre-treatment snag, and control; Phase II treatments included downed CWD addition (downed CWD volume increased 5-fold), snag addition (standing CWD volume increased 10-fold), all CWD removal (all CWD removed), and control. Amphibian and anuran capture rates were greater in control than all CWD removal plots during study Phase I. In Phase II, reptile diversity and richness were greater in downed CWD addition and all CWD removal than snag addition treatments. Capture rate of Rana sphenocephala was greater in all CWD removal treatment than downed CWD addition treatment. The dominant amphibian and snake species captured are adapted to burrowing in sandy soil or taking refuge under leaf litter. Amphibian and reptile species endemic to upland southeastern Coastal Plain pine forests may not have evolved to rely on CWD because the humid climate and short fire return interval have resulted in historically low volumes of CWD.

Schenk, H.J. et al. 2008. Hydraulic integration and shrub growth form linked across continental aridity gradients. Proceedings of the National Academy of Sciences of the United States of America. 105(32): 11248-11253.

Abstract
Both engineered hydraulic systems and plant hydraulic systems are protected against failure by resistance, reparability, and redundancy. A basic rule of reliability engineering is that the level of independent redundancy should increase with increasing risk of fatal system failure. Here we show that hydraulic systems of plants function as predicted by this engineering rule. Hydraulic systems of shrubs sampled along two transcontinental aridity gradients changed with increasing aridity from highly integrated to independently redundant modular designs. Shrubs in humid environments tend to be hydraulically integrated, with single, round basal stems, whereas dryland shrubs typically have modular hydraulic systems and multiple, segmented basal stems. Modularity is achieved anatomically at the vessel-network scale or developmentally at the whole-plant scale through asymmetric secondary growth, which results in a semiclonal or clonal shrub growth form that appears to be ubiquitous in global deserts.

Schofield, K.A., Pringle, C.M., Meyer, J.L., Rosi-Marshall, E.J. 2008. Functional redundancy of stream macroconsumers despite differences in catchment land use. Freshwater Biology, 53: 2587-2599

Abstract
1. The conversion of forested landscapes to agriculture and, increasingly, to suburban and urban development significantly affects the structure and function of both terrestrial and aquatic ecosystems. While a growing body of research is examining how biotic communities change in response to human alteration of landscapes, less is known about how these changes in community structure affect biotic interactions. 2. The objective of this study was to examine top-down control by macroconsumers (fish and crayfish) across a human-impacted landscape. We predicted that changes in stream macroconsumers and physicochemical characteristics associated with increased catchment development (e.g. decreased abundance of fish that are obligate benthic invertivores, increased sedimentation) would diminish top-down control of benthic insects. We expected that effects on algal assemblages would be more variable, with increased top-down control at sites dominated by algivorous fish and diminished control elsewhere. To test these predictions, we experimentally excluded fish and crayfish from areas of the bed of five streams whose catchments ranged from 100% to <50% forested, and examined the effects of exclusion on benthic insects and algae. 3. Despite cross-site differences in physical, chemical and biological characteristics, the outcome of our experiments was consistent across five sites representing a range of catchment development. Across all sites, macroconsumers reduced total insect biomass, largely due to decreases in Chironomidae and Hydropsychidae larvae. Macroconsumers also affected algal assemblages, reducing chlorophyll-a and the proportion of upright and filamentous diatoms (e.g. Melosira, Cymbella) but increasing the proportion of adnate diatoms (e.g. Achnanthes) across all sites. 4. We expected that differences in factors such as macroconsumer assemblage composition, nutrient and light availability and sedimentation would result in variable responses to macroconsumer exclusion in the five streams. Contrary to these expectations, only one response variable (ash-free dry mass) showed a statistically significant interaction (i.e. site · exclusion) effect. Most responses to exclusion were relatively consistent, suggesting functional redundancy in assemblages of macroconsumers among the sites despite differences in catchment land use.

Skyfield, J.P., Grossman, G.D. 2008. Microhabitat use, movements and abundance of gilt darters (Percina evides) in southern Appalachian (USA) streams. Ecology of Freshwater Fish. 17: 219-230

Abstract
We examined microhabitat use by gilt darters (Percina evides) in two streams in the south-eastern USA. Darters were over-represented in erosional microhabitats with higher average velocities and more cobble.Male darters tended to show stronger selection than females. Size-based analyses showed that larger (‡60 mm) gilt darters tended to use microhabitats with more heterogeneous substrata and more boulder than smaller (£59 mm) darters. We also conducted a short-term movement study and calculated population estimates based on mark–recapture data in autumn 2005. Darters moved both long and short distances with 40% of all recaptures occurring within 5 m of the initial capture point. Using Program mark and model-averaged parameter estimates gilt darter density was 0.31 dartersÆm)2 (225 darters ? 730 m2). Conservation of this species will require the preservation of erosional habitats in streams.

Sun, G., Zuo, C., Liu, S., Liu, M., McNulty, S.G., Vose, J.M. 2008. Watershed Evapotranspiration Increased Due To Changes In Vegetation Composition And Structure Under A Subtropical Climate. Journal of the American Water Resources Association 44(5): 1164-1175.

Abstract
Natural forests in southern China have been severely logged due to high human demand for timber, food, and fuels during the past century, but are recovering in the past decade. The objective of this study was to investigate how vegetation cover changes in composition and structure affected the water budgets of a 9.6-km2 Dakeng watershed located in a humid subtropical mountainous region in southern China. We analyzed 27 years (i.e., 1967-1993) of streamflow and climate data and associated vegetation cover change in the watershed. Land use / land cover census and Normalized Difference of Vegetation Index (NDVI) data derived from remote sensing were used to construct historic land cover change patterns. We found that over the period of record, annual streamflow (Q) and runoff / precipitation ratio did not change significantly, nor did the climatic variables, including air temperature, Hamon’s potential evapotranspiration (ET), pan evaporation, sunshine hours, and radiation. However, annual ET estimated as the differences between P and Q showed a statistically significant increasing trend. Overall, the NDVI of the watershed had a significant increasing trend in the peak spring growing season. This study concluded that watershed ecosystem ET increased as the vegetation cover shifted from low stock forests to shrub and grasslands that had higher ET rates. A conceptual model was developed for the study watershed to describe the vegetation cover-streamflow relationships during a 50-year time frame. This paper highlighted the importance of eco-physiologically based studies in understanding transitory, nonstationary effects of deforestation or forestation on watershed water balances.

Upchurch, R., Chiu, C.Y., Everett, K., Dyszynski, G., Coleman, D.C., Whitman, W.B. 2008. Differences in the composition and diversity of bacterial communities from agricultural and forest soils. Soil Biology & Biochemistry, 40(6): 1294-1305.

Abstract
Differences in the bacterial communities of soils caused by disturbances and land management were identified in rRNA gene libraries prepared from conventional tilled (CT) and no tilled (NT) cropland, a successional forest after 30 y of regrowth (NF) and an old forest of 465 y (OF) at Horseshoe Bend, in the southern Piedmont of Georgia (USA). Libraries were also prepared from forests after 80 y of regrowth at the Coweeta Long Term Ecological Research site (CWT) in the Southern Appalachians of western North Carolina (USA). The composition of the bacterial communities in cropland soils differed from those of the Horseshoe Bend OF and CWT forest soils, and many of the most abundant OTUs were different. Likewise, the diversity of bacterial communities from forest was less than that from cropland. The lower diversity in forest soils was attributed to the presence of a few, very abundant taxa in forest soils that were of reduced abundance or absent in cropland soils. After 30 y of regrowth, the composition of the bacterial soil community of the NF was similar to that of the OF, but the diversity was greater. These results suggested that the bacterial community of soil changes slowly within the time scale of these studies. In contrast, the composition and diversity of the bacterial communities in the Horseshoe Bend OF and Coweeta soils were very similar. Thus, this forest soil bacterial community was widely distributed in spite of the differences in soil properties, vegetation, and climate as well as resilient to disturbances of the above ground vegetation.

Valett, H.M., Thomas, S.A., Mulholland, P.J., Webster, J.R., Dahm, C.N., Fellows, C.S., Crenshaw, C.L., and C.G. Peterson. 2008. Endogenous and exogenous control of ecosystem function: N cycling in headwater streams. Ecology (In Press).

Abstract
Allochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of 15N as nitrate in six streams differing in riparian–stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in 15N flux. Respiration (R) and gross primary production (GPP) were measured with whole-stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open-canopied streams, areal uptake (U; lg Nm2s1) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (vf; mm/s) was closely related to R. In contrast to open-canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in-stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.

Walker, J.F., O.K. Miller Jr., and J.L. Horton. 2005. Hyperdiversity of ectomycorrhizal fungus assemblages on oak seedlings in mixed forests in the southern Appalachian mountains. Molecular Ecology. (14): 829-838.

Abstract
Diversity of ectotrophic mycobionts on outplanted seedlings of two oak species (Quercus rubra and Quercus prinus) was estimated at two sites in mature mixed forests in the southern Appalachian Mountains by sequencing nuclear 5.8S rRNA genes and the flanking internal transcribed spacer regions I and II (ITS). The seedlings captured a high diversity of mycorrhizal ITS-types and late-stage fungi were well represented.

Walker, J.F., O.K. Miller Jr., and J.L. Horton. 2008. Seasonal dynamics of ectomycorrhizal fungus assemblages on oak seedlings in the southeastern Appalachian mountains. Mycorrhiza (2008) 18:123–132.

Abstract
The potential for seasonal dynamics in ectomycorrhizal (EM) fungal assemblages has important implications for the ecology of both the host trees and the fungal associates. We compared EM fungus distributions on root systems of out-planted oak seedlings at two sites in mixed southeastern Appalachian Mountain forests at the Coweeta Hydrologic Laboratory in North Carolina, from samples taken in mid-July and early September. Species level EM fungus type specificity, and identification in some cases, was enabled by direct sequencing of the mycobionts from the seedling roots.

Warren, R.J. 2008. Mechanisms driving understory evergreen herb distributions across slope aspects: as derived from landscape position. Plant Ecology. 198(2): 297-308.

Abstract
In the Northern Hemisphere, the surface of south-facing slopes orients toward the sun and thus receives a greater duration and intensity of solar irradiation, resulting in a relatively warmer, drier microclimate and seasonal environmental extremes.This creates potentially detrimental conditions for evergreen plants which must endure the full gamut of conditions. I hypothesize that (1) increased southerly aspect will correlate negatively with evergreen understory plant distributions; (2) derived environmental variables (summer and winter light and heat load) will predict variance in evergreen distributions as well as topographic position (aspect, slope, and elevation) and (3) winter light will best predict evergreen understory plant distributions. In order to test these hypotheses, survey data were collected characterizing 10 evergreen understory herb distributions (presence, abundance, and reproduction) as well as the corresponding topographical information across north- and south-facing slopes in the North Carolina mountains and Georgia piedmont. The best predictive models were selected using AIC, and Bayesian hierarchical generalized linear models were used to estimate the strength of the retained coefficients. As predicted, evergreen understory herbs occurred and reproduced less on south-facing than north-facing slopes, though slope and elevation also had robust predictive power, and both discriminated well between evergreen species. While the landscape variables explained where the plants occurred, winter light and heat load provided the best explanation why they were there. Evergreen plants likely are limited on south-facing slopes by low soil moisture combined with high temperatures in summer and high irradiance combined with lower temperatures in winter. The robust negative response of the understory evergreen herbs to increased winter light also suggested that the winter rather than the summer (or growing season) environment provided the best predictive power for understory evergreen distributions, which has substantive implications for predicting responses to global climate change.

Wooten, R.M., Gillon, K.A., Witt, A.C. et al. (2008) Geologic, geomorphic, and meteorological aspects of debris flows triggered by Hurricanes Frances and Ivan during September 2004 in the Southern Appalachian Mountains of Macon County, North Carolina (southeastern USA) Landslides 5: 31. https://doi.org/10.1007/s10346-007-0109-9

Abstract
In September 2004, rain from the remnants of Hurricanes Frances and Ivan triggered at least 155 landslides in the Blue Ridge Mountains of North Carolina. At least 33 debris flows occurred in Macon County, causing 5 deaths, destroying 16 homes, and damaging infrastructure. We mapped debris flows and debris deposits using a light-detecting and ranging digital elevation model, remote imagery and field studies integrated in a geographic information system. Evidence of past debris flows was found at all recent debris flow sites. Orographic rainfall enhancement along topographic escarpments influenced debris flow frequency at higher elevations. A possible trigger for the Wayah and fatal Peeks Creek debris flows was a spiral rain band within Ivan that moved across the area with short duration rainfall rates of 150–230 mm/h. Intersecting bedrock structures in polydeformed metamorphic rock influence the formation of catchments within structural–geomorphic domains where debris flows originate.

Zeppel, M., C.M.O. Macinnis-Ng, C.R. Ford, and Emaus, D. 2008. The response of sap flow to pulses of rain in a temperate Australian woodland. Plant Soil. 305: 121-130.

Abstract
In water-limited systems, pulses of rainfall can trigger a cascade of  plant physiological responses. However, the timing and size of the physiological response can vary depending on plant and environmental characteristics, such as rooting depth, plant size, rainfall amount, or antecedent soil moisture. We investigate the influence of pulses of rainfall on the response of sap flow of two dominant evergreen tree species, Eucalyptus crebra (a broadleaf) and Callitris glaucophylla (a needle leaved tree), in a remnant open woodland in eastern Australia. Sap flow data were collected using heat-pulse sensors installed in six trees of each species over a 2 year period which encompassed the tail-end of a widespread drought. Our objectives were to estimate the magnitude that a rainfall pulse had to exceed to increase tree water use (i.e. define the threshold response), and to determine how tree and environmental factors influenced the increase in tree water use following a rainfall pulse.

Beckage, B., L. Joseph, P. Belisle, D.B. Wolfson, and W.J. Platt. 2007. Bayesian change-point analyses in ecology. New Phytologist. 174: 456-467.

Abstract
Ecological and biological processes can change from one state to another once a threshold has been crossed in space or time. Threshold responses to incremental changes in underlying variables can characterize diverse processes from climate change to the desertification of arid lands from overgrazing. Simultaneously estimating the location of thresholds and associated ecological parameters can be difficult: ecological data are often ‘noisy’, which can make the identification of the locations of ecological thresholds challenging. We illustrate this problem using two ecological examples and apply a class of statistical models well-suited to addressing this problem. We first consider the case of estimating allometric relationships between tree diameter and height when the trees have distinctly different growth modes across life-history stages. We next estimate the effects of canopy gaps and dense understory vegetation on tree recruitment in transects that transverse both canopy and gap conditions. The Bayesian change-point models that we present estimate both threshold locations and the slope or level of ecological quantities of interest, while incorporating uncertainty in the change-point location into these estimates. This class of models is suitable for problems with multiple thresholds and can account for spatial or temporal autocorrelation.

Burcher, C.L., H.M. Valett, and E.F. Benfield. 2007. The land-cover cascade: Relationships coupling land and water. Ecology. 88(1): 228-242.

Abstract
We introduce the land-cover cascade (LCC) as a conceptual framework to quantify the transfer of land-cover-disturbance effects to stream biota. We hypothesize that disturbance is propagated through multivariate systems through key variables that transform a disturbance and pass a reorganized disturbance effect to the next hierarchical level where the process repeats until ultimately affecting biota. We measured 31 hydrologic, geomorphic, erosional, and substrate variables and 26 biotic responses that have been associated with land-use disturbance in third- and fourth-order streams in the Blue Ridge physiographic province in western North Carolina (USA). Regression analyses reduced this set of variables to include only those that responded to land cover and/or affected biota. From this reduced variable set, hypotheses were generated that predicted the disturbance pathways affecting each biotic response following the land-cover-cascade design. Cascade pathways began with land cover and ended with biotic responses, passing through at least one intermediate ecosystem abiotic component. Cascade models were tested for predictive ability and goodness-of-fit using path analysis. Biota were influenced by near-stream urban, agricultural, and forest land cover as propagated by hydrologic (e.g., discharge), geomorphic (e.g., stream bank height), erosional (e.g., suspended sediments), and depositional streambed (e.g., substrate size) features occurring along LCC pathways, reflecting abiotic mechanisms mediating land-cover disturbance. Our results suggest that communities are influenced by land-cover change indirectly through a hierarchy of associated abiotic components that propagate disturbance to biota. More generally, the land-cover cascade concept and experimental framework demonstrate an organized approach to the generic study of cascades and the complex relationships between landscapes and streams.

Clark, J.S., M. Dietze, S. Chakraborty, P.K. Agarwal, I. Ibanez, S. LaDeau, and M. Wolosin. 2007. Resolving the biodiversity paradox. Ecology. 10: 647-662.

Abstract
The paradox of biodiversity involves three elements, (i) mathematical models predict that species must differ in specific ways in order to coexist as stable ecological communities, (ii) such differences are difficult to identify, yet (iii) there is widespread evidence of stability in natural communities. Debate has centred on two views. The first explanation involves tradeoffs along a small number of axes, including 'colonization-competition', resource competition (light, water, nitrogen for plants, including the 'successional niche'), and life history (e.g. high-light growth vs. low-light survival and few large vs. many small seeds). The second view is neutrality, which assumes that species differences do not contribute to dynamics. Clark et. al. (2004) presented a third explanation, that coexistence is inherently high dimensional, but still depends on species differences. We demonstrate that neither traditional low-dimensional tradeoffs nor neutrality can resolve the biodiversity paradox, in part by showing that they do not properly interpret stochasticity in statistical and in theoretical models.

Clark, J.S., M. Wolosin, M. Dietze, I. Ibanez, S. LaDeau, M. Welsh, and B. Kloeppel. 2007. Tree growth inference and prediction from diameter censuses and ring widths. Ecological Applications 17(7): 1942-1953.

Abstract
Estimation of tree growth is based on sparse observations of tree diameter, ring widths, or increments read from a dendrometer. From annual measurements on a few trees (e.g., increment cores) or sporadic measurements from many trees (e.g., diameter censuses on mapped plots), relationships with resources, tree size, and climate are extrapolated to whole stands. There has been no way to formally integrate different types of data and problems of estimation that result from (1) multiple sources of observation error, which frequently result in impossible estimates of negative growth, (2) the fact that data are typically sparse (a few trees or a few years), whereas inference is needed broadly (many trees over many years), (3) the fact that some unknown fraction of the variance is shared across the population, and (4) the fact that growth rates of trees within competing stands are not independent. We develop a hierarchical Bayes state space model for tree growth that addresses all of these challenges, allowing for formal inference that is consistent with the available data and the assumption that growth is nonnegative. Prediction follows directly, incorporating the full uncertainty from inference with scenarios for ‘‘filling the gaps’’ for past growth rates and for future conditions affecting growth. An example involving multiple species and multiple stands with tree-ring data and up to 14 years of tree census data illustrates how different levels of information at the tree and stand level contribute to inference and prediction.

Cook, D., DeCrescenzo, E., Upchurch, R., Peterson, J. 2007. Isolation of Polymer-Degrading Bacteria and Characterization of the Hindgut Bacterial Community from the Detritus-Feeding Larvae of Tipula abdominalis (Diptera: Tipulidae). Applied and Environmen

Abstract
The Tipula abdominalis larval hindgut microbial community presumably facilitates digestion of the lignocellulosic diet. The microbial community was investigated through characterization of bacterial isolates and analysis of 16S rRNA gene clone libraries. This initial study revealed novel bacteria and provides a framework for future studies of this symbiosis.

Cross, W., Wallace, J., Rosemond, A. 2007. Nutrient enrichment reduces constraints on material flows in a detritus-based food web. Ecology, 88(10): 2563-2575

Abstract
Most aquatic and terrestrial ecosystems are experiencing increased nutrient availability, which is affecting their structure and function. By altering community composition and productivity of consumers, enrichment can indirectly cause changes in the pathways and magnitude of material flows in food webs. These changes, in turn, have major consequences for material storage and cycling in the ecosystem. Understanding mechanisms and predicting consequences of nutrient-induced changes in material flows requires a quantitative food web approach that combines information on consumer energetics and consumer–resource stoichiometry. We examined effects of a whole-system experimental nutrient enrichment on the trophic basis of production and the magnitude and pathways of carbon ©, nitrogen (N), and phosphorus (P) flows in a detritus-based stream food web. We compared the response of the treated stream to an adjacent reference stream throughout the study. Dietary composition and elemental flows varied considerably among invertebrate functional feeding groups. During nutrient enrichment, increased flows of leaf litter and amorphous detritus to shredders and gatherers accounted for most of the altered flows of C from basal resources to consumers. Nutrient enrichment had little effect on patterns of material flows but had large positive effects on the magnitude of C, N, and P flows to consumers (mean increase of 97% for all elements). Nutrient-specific food webs revealed similar flows of N and P to multiple functional groups despite an order of magnitude difference among groups in consumption of C. Secondary production was more strongly related to consumption of nutrients than C, and increased material flows were positively related to the degree of consumer–resource C:P and C:N imbalances. Nutrient enrichment resulted in an increased proportion of detrital C inputs consumed by primary consumers (from ;15% to 35%) and a decreased proportion of invertebrate prey consumed by predators (from ;80% to 55%). Our results demonstrate that nutrient enrichment of detritus-based systems may reduce stoichiometric constraints on material flows, increase the contribution of consumers to C, N, and P cycling, alter the proportion of C inputs metabolized by consumers, and potentially lead to reduced ecosystem-level storage of C.

Cross, W.F., J.B. Wallace, and A.D. Rosemond. 2007. Nutrient enrichment reduces constraints on material flows in a detrius-based food web. Ecology. 88(10): 2563-2575.

Abstract
Most aquatic and terrestrial ecosystems are experiencing increased nutrient availability, which is affecting their structure and function. By altering community composition and productivity of consumers, enrichment can indirectly cause changes in the pathways and magnitude of material flows in food webs. These changes, in turn, have major consequences for material storage and cycling in the ecosystem. Understanding mechanisms and predicting consequences of nutrient-induced changes in material flows requires a quantitative food web approach that combines information on consumer energetics and consumer–resource stoichiometry. We examined effects of a whole-system experimental nutrient enrichment on the trophic basis of production and the magnitude and pathways of carbon (C), nitrogen (N), and phosphorus (P) flows in a detritus-based stream food web.

Dietze, M. and J. S. Clark. 2007. Rethinking gap dynamics: the impact of damaged trees and sprouts. Ecological Monographs 78:331-347.

Abstract
Understanding the manner in which changes in disturbance regimes will affect forest biodiversity is an important goal of global change research. Prevailing theories of recruitment after disturbance center on the role of pioneer species; predictions of forest biodiversity focus almost exclusively on dispersal and shade tolerance while vegetative reproduction is virtually omitted from models and serious discussions of the topic. However, the persistence of live damaged trees increases understory shade, generates fine-scale environmental heterogeneity, and moderates ecosystem responses to damage, while the sprouting of damaged trees offers a shortcut to reestablishment of the canopy. While a number of studies document snapshots of post-disturbance vegetative reproduction, we lack an understanding of the underlying demographic processes needed in order to both comprehend and predict observed patterns. In this study we quantify the abundance, competitive ability, and interspecific variability of vegetative reproduction in 18 replicated experimental gaps in the southern Appalachians and Carolina Piedmont, USA, in order to assess the potential role of sprouting in driving gap dynamics.

Diez, J.M. 2007. Hierarchical patterns of symbiotic orchid germination linked to adult proximity and environmental gradients. Journal of Ecology. 95: 159-170.

Abstract
(1) The recruitment stage can be critical in determining plant population dynamics, as juveniles encounter a range of abiotic and biotic stressors in the environments where they land after dispersal, and often experience high mortality rates. Although both abiotic and biotic constraints on recruitment are often assumed to operate at multiple scales, these relationships are rarely quantified in ways that enable prediction of recruitment dynamics across environmental gradients. (2) In plants such as orchids, an important bottleneck on recruitment may arise from an obligate dependence on mycorrhizal fungi in order to reach photosynthetic stage. Very little is known, however, about the factors controlling the distribution of the fungi or how fungal distributions may constrain orchid recruitment and distributions. (3) In this study, seed introduction experiments were used to test for relationships between symbiotic germination success of an orchid, Goodyera pubescens, and both proximity to adult orchids and soil abiotic conditions. Experiments were linked to ongoing demographic monitoring across a large environmental gradient to place patterns of germination better in the context of longer-term demographic patterns. (4) A hierarchical Bayesian statistical framework was used to evaluate explicitly how recruitment varies across scales and how this variation is explained by key abiotic variables. This framework was further utilized to link hypothesis testing to model building, and thereby improve our ability to make predictions across a range of environmental conditions. (5) At a microsite scale (< 4 m2) strong evidence was found for decreasing germination success further from adult plants. At distances greater than 1 m from adults, increased germination success was associated with higher soil moisture, higher organic content and lower pH, although the strength of these relationships varied regionally. Patterns of symbiotic germination success were also highly correlated with observed recruitment patterns at the population level. (6) Explicitly linking plant recruitment to underlying abiotic gradients and key biotic interactions using a hierarchical, predictive modelling framework is essential for understanding basic plant population processes and building capacity to make predictions of how species and communities may respond to environmental changes.

Diez, J.M., and H.R. Pulliam. 2007. Hierarchical analysis of species distributions and abundance across environmental gradients. Ecology 88(12): 3144-3152.

Abstract
Abiotic and biotic processes operate at multiple spatial and temporal scales to shape many ecological processes, including species distributions and demography. Current debate about the relative roles of niche-based and stochastic processes in shaping species distributions and community composition reflects, in part, the challenge of understanding how these processes interact across scales. Traditional statistical models that ignore autocorrelation and spatial hierarchies can result in misidentification of important ecological covariates. Here, we demonstrate the utility of a hierarchical modeling framework for testing hypotheses about the importance of abiotic factors at different spatial scales and local spatial autocorrelation for shaping species distributions and abundances. For the two orchid species studied, understory light availability and soil moisture helped to explain patterns of presence and abundance at a microsite scale (<4 m2), while soil organic content was important at a population scale (<400 m2). The inclusion of spatial autocorrelation is shown to alter the magnitude and certainty of estimated relationships between abundance and abiotic variables, and we suggest that such analysis be used more often to explore the relationships between species life histories and distributions. The hierarchical modeling framework is shown to have great potential for elucidating ecological relationships involving abiotic and biotic processes simultaneously at multiple scales.

Eggert, S.L., Wallace, J.B. 2007. Wood biofilm as a food resource for stream detritivores. Limnology and Oceanography, 52(3): 1239-1245.

Abstract
Published assimilation efficiencies indicate that leaf detritus is a more nutritious food for stream invertebrates than wood. Some studies, however, suggest that wood and wood biofilms (epixylon) may be an important but overlooked resource. We measured assimilation efficiencies of three detritivores for leaves and epixylon and compared attributes of grazed versus ungrazed wood epixylon to assess its use by detritivores. Pycnopsyche gentilis (Trichoptera), Tipula abdominalis (Diptera), and Tallaperla spp. (Plecoptera) assimilated epixylon more efficiently (26–36%) than leaf detritus (9–17%). Epixylon assimilation efficiencies were T. abdominalis . Tallaperla spp. . P. gentilis. Grazed wood had significantly lower microbial respiration rates, bacteria densities and biomass, fungal and chlorophyll a biomass, and biofilm ash-free dry mass than ungrazed wood, indicating that detritivores fed on epixylon. Detritivores ingested leaves at a higher rate (0.09–0.47 g g21 d21) than epixylon (0.04–0.07 g g21 d21). Assimilation rates, which incorporate both assimilation efficiency and ingestion rate, however, indicated that Tallaperla spp. And T. abdominalis were better able to use epixylon than leaves, whereas P. gentilis was more efficient at using leaves. Wood biofilm is readily ingested and assimilated by some stream detritivores and may serve as an important but overlooked food resource in stream food webs.

Entrekin, S.A., J.B. Wallace, and S.L. Eggert. 2007. The response of Chironomidae (Diptera) to a long-term exclusion of terrestrial organic matter. Hydrobiologia. 575: 401-413.

Abstract
We examined the effects of a seven-year detrital exclusion on chironomid assemblages in an Appalachian headwater stream. We hypothesized that litter exclusion would lead to a reduction in all chironomids at both the subfamily and generic levels because organic matter serves as both food and habitat in these headwater streams. Tanytarsini total abundance and biomass significantly declined after litter exclusion. Before litter exclusion, Tanytarsini average abundance was 4271 + 1135 S.E. m-2 and 625 + 98 after litter exclusion. Biomass was 3.57 + 0.96 mg AFDM m-2 before litter exclusion and 1.03 + 0.9 after exclusion. In contrast, Orthocladiinae abundance and biomass did not change because a psammanophilic chironomid, Lopescladius sp., and other Orthocladiinae genera did not decline significantly. Overall chironomid taxa richness and diversity did not change as a result of litter exclusion. However, Canonical Correspondence Analysis (CCA) of genus-level biomass did show a clear separation between the litter exclusion stream and a reference stream. Separation of taxa between the two streams was due to differences in fine (r2 = 0.39) and coarse (r2 = 0.36) organic matter standing stocks and the proportion of small inorganic substrates (r2 = 0.39) present within a sample. As organic matter declined in the litter exclusion stream, overall chironomid biomass declined and the chironomid community assemblage changed. Tanytarsini were replaced by Orthocladiinae in the litter exclusion stream because they were better able to live and feed on biofilm associated with inorganic substrates.

Ford, C.R., and J.M. Vose. 2007. Tsuga Canadensis (L.) Carr. mortality will impact hydrologic processes in southern Appalachian forest ecosystems. Ecological Applications. 17(4): 1156-1167.

Abstract
(1) Eastern hemlock (Tsuga canadensis (L.) Carr.) is one of the principal riparian and cove canopy species in the southern Appalachian Mountains. Throughout its range, eastern hemlock is facing potential widespread mortality from the hemlock woolly adelgid (HWA). If HWA-induced eastern hemlock mortality alters hydrologic function, land managers will be challenged to develop management strategies that restore function or mitigate impacts. To estimate the impact that the loss of this forest species will have on the hydrologic budget, we quantified and modeled transpiration over a range of tree sizes and environmental conditions. We used heat dissipation probes, leaf-level gas-exchange measurements, allometric scaling, and time series modeling techniques to quantify wholetree and leaf-level transpiration (EL) of eastern hemlock. We monitored trees ranging from 9.5 to 67.5 cm in diameter along a riparian corridor in western North Carolina, USA during 2004 and 2005. (2) Maximum rates of daily tree water use varied by diameter and height, with large trees transpiring a maximum of 178v186 kg H2O*tree-1*d-1. Values of EL could be predicted from current and lagged environmental variables. We forecasted eastern hemlock EL for inventoried stands and estimated a mean annual transpiration rate of 63.3 mm/yr for the hemlock component, with 50% being transpired in the winter and spring. In typical southern Appalachian stands, eastern hemlock mortality would thus reduce annual stand-level transpiration by ~10% and reduce winter and spring stand-level transpiration by ~30%. (3) Eastern hemlock in the southern Appalachians has two distinct ecohydrological roles: an evergreen tree that maintains year-round transpiration rates and a riparian tree that has high transpiration rates in the spring. No other native evergreen in the southern Appalachians will likely fill the ecohydrological role of eastern hemlock if widespread mortality occurs. With the loss of this species, we predict persistent increases in discharge, decreases in the diurnal amplitude of streamflow, and increases in the width of the variable source area.

Ford, C.R., J.M. Vose, M. Daley, and N. Phillips. 2007. Use of water by eastern hemlock: implications for systemic insecticide application. Arboriculture & Urban Forestry. 33(6): 421-427.

Abstract
The hemlock woolly adelgid (HWA; Adelges tsugae Annand) is causing widespread decline and mortality of eastern hemlock (Tsuga canadensis (L.) Carr.) throughout most of the range of eastern hemlock. Stem injection of insecticide is widely used as a chemical control measure, but the effectiveness of this method depends on the hydraulic characteristics of individual trees. We present data quantifying the distribution of water flux within the stems and the seasonal variability of daily water use of eastern hemlock trees growing in New England, U.S. and the southern Appalachians.

Ford, C.R., N. Wurzburger, R.L. Hendrick, and R.O. Teskey. 2007. Soil DIC uptake and fixation in Pinus taeda seedlings and its C contribution to plant tissue and ectomycorrhizal fungi. Tree Physiology. 27: 375-383.

Abstract
Plants can acquire carbon from sources other than atmospheric carbon dioxide (CO2), including soil-dissolved inorganic carbon (DIC). Although the net flux of CO2 is out of the root, soil DIC can be taken up by the root, transported within the plant, and fixed either photosynthetically or anaplerotically by plant tissues. We tested the ability of Pinus taeda L. seedlings exposed to 13C-labeled soil DIC and two NH+4 availability regimes to take up and fix soil DIC. We also measured the concentration and distribution of the fixed soil DIC within the plant and mycrorrhizal tissues, and quantified the contribution of soil DIC to whole-plant carbon (C) gain. Seedlings exposed to labeled DIC were significantly enriched in 13C compared with seedlings exposed to unlabeled DIC (6.7 versus -31.7%). Fixed soil DIC was almost evenly distributed between above- and belowground biomass (55 and 45%, respectively), but was unevenly distributed among tissues. Aboveground stem tissue contained 65% of the fixed soil DIC but represented only 27% of the aboveground biomass, suggesting either corticular photosynthesis or preferential stem allocation. Belowground, soil DIC had the greatest effect (measured as 13C enrichment) on the C pool of rapidly growing nonmycorrhizal roots. Soil DIC contributed ~0.8% to whole-plant C gain, and ~1.6% to belowground C gain. We observed a slight but nonsignificant increase in both relative C gain and the contribution of soil DIC to C gain in NH+4-fertilized seedlings. Increased NH+4 availability significantly altered the distribution of fixed soil DIC among tissue types and increased the amount of fixed soil DIC in ectomycorrhizal roots by 130% compared with unfertilized seedlings. Increased NH+4 availability did not increase fixation of soil DIC in nonmycorrhizal roots, suggesting the NH+4 assimilation may be concentrated in ectomycorrhizal fungal tissues, reflecting greater anaplerotic demands. Soil DIC is likely to contribute only a small amount of C to forest trees, but it may be important in C fixation processes of specific tissues, such as newly formed stems and fine roots, and ectomycorrhizal roots assimilating NH+4.

Ford, C.R., R.M. Hubbard, B.D. Kloeppel, and J.M. Vose. 2007. A comparison of sap flux-based evapotranspiration estimates with catchment-scale water balance. Agricultural and Forest Meteorology. 145: 176-185.

Abstract
Many researchers are using sap flux to estimate tree-level transpiration, and to scale to stand- and catchment-level transpiration; yet studies evaluating the comparability of sap flux-based estimates of transpiration (Et) with alternative methods for estimating Et at this spatial scale are rare. Our ability to accurately scale from the probe to the tree to the watershed has not yet been demonstrated, nor do we know the relative impact of the main sources of variability on our scaled estimates. Accounting for the variability in the radial distribution of sap flux within the sapwood, the variability of transpiration among trees and between plots within the catchment, and the variability in stand density, sapwood area, and leaf area are critical for making landscape inferences about transpiration. During 2004 and 2005, we continuously monitored 40 trees in three plots within a 13.5-ha gauged watershed comprising a 50-year-old eastern white pine plantation within the Coweeta Basin in western North Carolina, USA. We scaled sap flux-based estimates of stand transpiration (Et) and surface area-based estimates of stand interception (Ei) to the catchment and compared these with water balance estimates of evapotranspiration (E, precipitation minus runoff, P Ro). For both years, the sum of sap flux scaled Et and Ei were 14 and 7% lower that evapotranspiration estimated from P Ro. Our results show that a considerable amount of variation exists at each scaling step encountered; however, a simple scaling exercise revealed that omitting among plot variation affected the sap flux scaled Et estimate by 48%. Thus, the largest source of variability in scaling to the landscape was landscape variation in stand density and sapwood area.

Freeman, M.C., Pringle, C.M., Jackson, C.R. 2007. Hydrologic Connectivity and the Contribution of Stream Headwaters to Ecological integrity at Regional Scales. Journal of the American Water Resources Association 43(1): 5-14.

Abstract
Cumulatively, headwater streams contribute to maintaining hydrologic connectivity and ecosystem integrity at regional scales. Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. Headwater streams compose over two-thirds of total stream length in a typical river drainage and directly connect the upland and riparian landscape to the rest of the stream ecosystem. Altering headwater streams, e.g., by channelization, diversion through pipes, impoundment and burial, modifies fluxes between uplands and downstream river segments and eliminates distinctive habitats. The large-scale ecological effects of altering headwaters are amplified by land uses that alter runoff and nutrient loads to streams, and by widespread dam construction on larger rivers (which frequently leaves free-flowing upstream portions of river systems essential to sustaining aquatic biodiversity). We discuss three examples of large-scale consequences of cumulative headwater alteration. Downstream eutrophication and coastal hypoxia result, in part, from agricultural practices that alter headwaters and wetlands while increasing nutrient runoff. Extensive headwater alteration is also expected to lower secondary productivity of river systems by reducing stream-system length and trophic subsidies to downstream river segments, affecting aquatic communities and terrestrial wildlife that utilize aquatic resources. Reduced viability of freshwater biota may occur with cumulative headwater alteration, including for species that occupy a range of stream sizes but for which headwater streams diversify the network of interconnected populations or enhance survival for particular life stages. Developing a more predictive understanding of ecological patterns that may emerge on regional scales as a result of headwater alterations will require studies focused on components and pathways that connect headwaters to river, coastal and terrestrial ecosystems. Linkages between headwaters and downstream ecosystems cannot be discounted when addressing large-scale issues such as hypoxia in the Gulf of Mexico and global losses of biodiversity.

Grace III, J.M., Clinton, B.D. 2007. Protecting Soil and Water in Forest Road Management. American Society of Agricultural and Biological Engineers, 50(5): 1579-1584

Abstract
The National Forest road system is the network that supports public recreation, which has become the primary use of the public lands. The pattern of use of National Forest roads for recreation has increased dramatically since the late 1940s and is expected to continue to increase beyond the rates observed today. However, research over the past 60 years clearly presents forest roads as a major source of sediment and soil erosion from forest watersheds. Threats to healthy forests have received increased attention in the past decade. In particular, roads, road management, and travel management will likely be critical to addressing the four threats to the health of the nation's forests and grasslands that were identified by USDA Forest Service. Road management is an important component in preserving and maintaining healthy forests throughout the nation. Sediment export from the existing forest road network is an issue of great concern in forest management. The objective of this article is to provide an overview of issues involved in managing the nation's public forest roads for the protection of soil and water. This article explores the benefit and efficacy of erosion mitigation, sediment control, and road BMPs in protecting soil and water. This article also suggests areas requiring additional research and development to satisfy the goals of protecting forest soil and water.

Gragson, T.L., Bolstad, P.V. 2007. A Local Analysis of Early-Eighteenth-Century Cherokee Settlement. Social Science History 31(3): 435-468

Abstract
Results of an original analysis of Cherokee town placement and population c. 1721 are presented. Period and contemporary information were analyzed using local statistics to produce multivalued, mappable characterizations of the intensity of the processes of town placement and population. The analysis focuses on the scale and the space in which these processes took place among the Cherokee in order to open the way for examining the legacy of human-induced environmental change in southern Appalachia.

Greenwood, J.L., Rosemond, A.D., Wallace, J.B., Cross, W.F., Weyers, H.S. 2007. Nutrients stimulate leaf breakdown rates and detritivore biomass: bottom-up effects via heterotrophic pathways. Oecologia, 151:637-649.

Abstract
Most nutrient enrichment studies in aquatic systems have focused on autotrophic food webs in systems where primary producers dominate the resource base. We tested the heterotrophic response to longterm nutrient enrichment in a forested, headwater stream. Our study design consisted of 2 years of pretreatment data in a reference and treatment stream and 2 years of continuous nitrogen (N) + phosphorus addition to the treatment stream. Studies were conducted with two leaf species that diVered in initial C:N, Rhododendron maximum (rhododendron) and Acer rubrum (red maple). We determined the eVects of nutrient addition on detrital resources (leaf breakdown rates, litter C:N and microbial activity) and tested whether nutrient enrichment aVected macroinvertebrate consumers via increased biomass. Leaf breakdown rates were ca. 1.5 and 3£ faster during the Wrst and second years of enrichment, respectively, in the treatment stream for both leaf types. Microbial respiration rates of both leaf types were 3£ higher with enrichment, and macroinvertebrate biomass associated with leaves increased ca. 2–3£ with enrichment. The mass of N in macroinvertebrate biomass relative to leaves tended to increase with enrichment up to 6£ for red maple and up to 44£ for rhododendron leaves. Lower quality (higher C:N) rhododendron leaves exhibited greater changes in leaf nutrient content and macroinvertebrate response to nutrient enrichment than red maple leaves, suggesting a unique response by diVerent leaf species to nutrient enrichment. Nutrient concentrations used in this study were moderate and equivalent to those in streams draining watersheds with altered land use. Thus, our results suggest that similarly moderate levels of enrichment may aVect detrital resource quality and subsequently lead to altered energy and nutrient Xow in detrital food webs.

Hawman, R. B. 2007. Crustal thickness variations across the Blue Ridge Mountains, southern Appalachians: An alternative procedure for migrating wide-angle reflection data. Bulletin of the Seismological Society of America. 98(1): 469-475.

Abstract
Migration of wide-angle reflections generated by quarry blasts suggests that crustal thickness increases from 38 km beneath the Carolina Terrane to 47-51 km along the southeastern flank of the Blue Ridge. The migration algorithm, developed for generating single-fold images from explosions and earthquakes recorded with isolated, short-aperture arrays, uses the localized slant stack as an intermediate data set. In contrast with other methods, it includes an interpretive step that is based on the assumption that all coherent P-wave energy consists of reflections from planar interfaces. Each sample in the slant stack is mapped into a planar, dipping segment with a length that is determined by the recording aperture. Migrated sections from within the Blue Ridge show increases in reflectivity at depths of 20 and 40 km. High apparent reflectivity from 40 to 50-55 km suggests a layered zone in the lower crust which is similar to models proposed for the Cumberland Plateau in Tennessee and the Adirondacks. The migration results are consistent with regional gravity data and with the occurrence of crustal roots beneath the Urals, another Paleozoic orogen.

Hutchins, Matthew. 2007. Effects of a prescribed burn on soil microarthropod populations at Nancytown, GA. UNCA Journal of undergraduate research. 74-80.

Abstract
In this study, the effects of a low-intensity prescribed burn were assessed on soil microarthropods by examining Collembola, Oribatid, Mesostigmata, and Prostigmata populations. Sampling was done for three consecutive years, including one year pre-burn. Mean microarthropod populations of all groups fluctuated over the three years, but further analysis indicated significant differences by date with population increases in 2006 for only Collembola and Oribatid populations.

Ibanez, I., J.S. Clark, S. LaDeau, and J. Hille Ris Lambers. 2007. Exploiting temporal variability to understand tree recruitment response to climate change. Ecological Monographs. 77(2): 163-177.

Abstract
 Predicting vegetation shifts under climate change is a challenging endeavor, given the complex interactions between biotic and abiotic variables that influence demographic rates. To determine how current trends and variation in climate change affect seedling establishment, we analyzed demographic responses to spatiotemporal variation to temperature and soil moisture in the southern Appalachian Mountains. We monitored seedling establishment for 10 years in five plots located along an elevational gradient of five dominant tree species: Acer rubrum, Betula spp., Liriodendron tulipifera, Nyssa sylvatica, and Quercus rubra. A hierarchical Bayes model allowed us to incorporate different sources of information, observation errors, and the inherent variability of the establishment process. From our analysis, spring temperatures and heterogeneity in soil moisture emerge as key drivers, and they act through nonlinear population demographic processes.

Jones, B., G.D. Grossman, D.C.I. Walsh, B.A. Porter, J.C. Avise, and A.C. Fiumera. 2007. Estimating differential reproductive success from nests of related individuals, with application to a study of the Mottled Sculpin, Cottus bairdi. Genetics. 176: 2427

Abstract
Understanding how variation in reproductive success is related to demography is a critical component in understanding the life history of an organism. Parentage analysis using molecular markers can be used to estimate the reproductive success of different groups of individuals in natural populations. Here we develop a model for comparing reproductive success among different groups of individuals that explicitly incorporates within-nest relatedness. We demonstrate that older adults are more likely to contribute to a nest and that females in the older age groups contribute more eggs to a nest than younger individuals.

Knoepp, J.D., and J.M. Vose. 2007. Regulation of nitrogen mineralization and nitrification in Southern Appalachian ecosystems:separating the relative importance of biotic vs. abiotic controls. Pedobiologia. 51: 89-97.

Abstract
Long-term measurements of soil nitrogen (N) transformations along an environmental gradient within the Coweeta Hydrologic Laboratory basin in western North Carolina showed a strong seasonal pattern and suggested that vegetation community type-through its influence on soil properties-was an important regulating factors. Our objective was to determine the relative effects of biotic vs. abiotic factors on soil N transformations. During the 1999 and 2000 growing season, we transplanted soil cores from each of the five gradient plots to all other gradient plots for their 28-day in situ incubation.

Kominoski, J.S., C.M. Pringle, B.A. Ball, M.A. Bradford, D.C. Coleman, D.B. Hall, and M.D. Hunter. 2007. Nonadditive effects of leaf litter species diversity on breakdown dynamics in a detritus-based stream. Ecology. 88(5): 1167-1176.

Abstract
Since species loss in predicted to be nonrandom, it is important to understand the manner in which those species that we anticipate losing interact with other species to affect ecosystem function. We tested whether litter species diversity measured as richness and composition, affects breakdown dynamics in a detritus-based stream. Using full-factorial analysis of single- and mixed-species leaf packs (15 possible combinations of four dominant litter species; red maple [Acer rubrum], tulip poplar [Liriodendron tulipifera], chestnut oak [Quercus prinus], and rhododendron [Rhododendron maximum]), we tested for single-species presence/absence (additive) or species interaction (nonadditive) effects on leaf pack breakdown rates, changes in litter chemistry, and microbial and macroinvertebrate biomass. Overall, we found significant nonadditive effects of litter species diversity on leaf pack breakdown rates, which were explained both by richness and by composition. Leaf packs containing higher litter species richness had faster breakdown rates, and antagonistic effects of litter species composition were observed when any two or three of the four litter species were mixed. Less-consistent results were obtained with respect to changes in litter chemistry and microbial and macroinvertebrate biomass. Our results suggest that loss of litter species diversity will decrease species interactions involved in regulating ecosystem function. To that end, loss of species such as eastern hemlock (Tsuga canadensis) accompanied by predicted changes in riparian tree species composition in the southeastern United States could have nonadditive effects on litter breakdown at the landscape scale.

Love, J.P., J.M. Vose, and K.J. Elliott. 2007. Effects of restoration burns on macroinvertebrates in southern Appalachian pine-oak forests. Journal of the North Carolina Academy of Science. 123(1): 22-34.

Abstract
Cover board arrays were used to measure the relative abundance of macroinvertebrates and terrestrial salamanders on prescribed burn and control sites in xeric southern Appalachians of northern Georgia and southeastern Tennessee pine-oak forests. Three microsite variables were measured at each cover board: cover board moisture level, temperature under the cover board, and soil moisture. . Soil moisture was significantly higher on the burn sites than the controls after the prescribed fire. Two groups of macroinvertebrates, Homoptera and Hymenoptera, were more abundant on the burn sites than the control sites. Coleoptera and Stylommatophora were significantly more abundant in riparian and low slope positions than upland positions; whereas, the other macroinvertebrate groups were not significantly related to slope position. Thirteen salamanders were found during the four sampling periods. Overall, there was little evidence of negative post-fire impacts on macroinvertebrates or salamanders.

McDONALD, R. I., YUAN-FARRELL, C. , FIEVET, C. , MOELLER, M. , KAREIVA, P. , FOSTER, D. , GRAGSON, T. , KINZIG, A. , KUBY, L. and REDMAN, C. (2007), Estimating the Effect of Protected Lands on the Development and Conservation of Their Surroundings. Conservation Biology, 21: 1526-1536. doi:10.1111/j.1523-1739.2007.00799.x

Abstract
The fate of private lands is widely seen as key to the fate of biodiversity in much of the world. Organizations that work to protect biodiversity on private lands often hope that conservation actions on one piece of land will leverage the actions of surrounding landowners. Few researchers have, however, examined whether protected lands do in fact encourage land conservation nearby or how protected lands affect development in the surrounding landscape. Using spatiotemporal data sets on land cover and land protection for three sites (western North Carolina, central Massachusetts, and central Arizona), we examined whether the existence of a protected area correlates with an increased rate of nearby land conservation or a decreased rate of nearby land development. At all sites, newly protected conservation areas tended to cluster close to preexisting protected areas. This may imply that the geography of contemporary conservation actions is influenced by past decisions on land protection, often made for reasons far removed from concerns about biodiversity. On the other hand, we found no evidence that proximity to protected areas correlates with a reduced rate of nearby land development. Indeed, on two of our three sites the development rate was significantly greater in regions with more protected land. This suggests that each conservation action should be justified and valued largely for what is protected on the targeted land, without much hope of broader conservation leverage effects.

McDonald, Robert I., Chris Yuan-Farrell, Charles Fievet, Matthias Moeller, Peter Kareiva, David Foster, Ted Gragson, Ann Kinzig, Lauren Kuby, and Charles Redman. 2007. Estimating the Effect of Protected Lands on the Development and Conservation of Their Surroundings. Conservation Biology 21(6): 1526-1536.

Abstract
The fate of private lands is widely seen as key to the fate of biodiversity in much of the world. Organizations that work to protect biodiversity on private lands often hope that conservation actions on one piece of land will leverage the actions of surrounding landowners. Few researchers have, however, examined whether protected lands do in fact encourage land conservation nearby or how protected lands affect development in the surrounding landscape. Using spatiotemporal data sets on land cover and land protection for three sites (western North Carolina, central Massachusetts, and central Arizona), we examined whether the existence of a protected area correlates with an increased rate of nearby land conservation or a decreased rate of nearby land development.

McMahon, S.M., and J.M. Diez. 2007. Scales of association: hierarchical linear models and the measurement of ecological systems. Ecology Letters. 10: 1-16.

Abstract
A fundamental challenge to understanding patterns in ecological systems lies in employing methods that can analyse, test and draw inference from measured associations between variables across scales. Hierarchical linear models (HLM) use advanced estimation algorithms to measure regression relationships and variancevcovariance parameters in hierarchically structured data. Although hierarchical models have occasionally been used in the analysis of ecological data, their full potential to describe scales of association, diagnose variance explained, and to partition uncertainty has not been employed. In this paper we argue that the use of the HLM framework can enable significantly improved inference about ecological processes across levels of organization. After briefly describing the principals behind HLM, we give two examples that demonstrate a protocol for building hierarchical models and answering questions about the relationships between variables at multiple scales. The first example employs maximum likelihood methods to construct a two-level linear model predicting herbivore damage to a perennial plant at the individual- and patch-scale; the second example uses Bayesian estimation techniques to develop a three-level logistic model of plant flowering probability across individual plants, microsites and populations. HLM model development and diagnostics illustrate the importance of incorporating scale when modelling associations in ecological systems and offer a sophisticated yet accessible method for studies of populations, communities and ecosystems. We suggest that a greater coupling of hierarchical study designs and hierarchical analysis will yield significant insights on how ecological processes operate across scales.

McTammany, M.E., E.F. Benfield, and J.R. Webster. 2007. Recovery of stream ecosystem metabolism from historical agriculture. Journal of the North American Benthological Society. 26(3): 532-545.

Abstract
Agriculture has influenced southern Appalachian streams for centuries, but recent socioeconomic trends in the region have led to extensive reforestation of agricultural land. Stream ecosystem metabolism might recover from agricultural influence as watersheds undergo reforestation, particularly when shade from terrestrial vegetation is restored. We determined historical (1950) and current (1993) forest cover in 2nd- and 3rd-order watersheds in 4 counties of the southern Appalachians using a geographic information system. Streams were placed into landuse categories based on % forested land cover in watersheds and riparian zones. Categories included forested (FOR; >98% forested) and 3 levels of agriculture (AG; ranging from 95% forest to <60% forest) with no change in % forest over the past 50 y, and 2 levels of recovery from agriculture (REC) indicated by reforestation after land abandonment. We selected 3 streams from each category and measured gross primary production (GPP) and 24-h respiration (R24) using a 2-station diurnal O2 change technique and gas releases to determine reaeration rates. We calculated net ecosystem production (NEP) and the ratio of GPP to R24 (P/R) to compare ecosystem energetics among landuse categories. We measured nutrient concentrations, photosynthetically active radiation (PAR), temperature (degree-days), suspended particle concentrations, and benthic algae (chlorophyll a and ash-free dry mass) to determine if these factors were affected by current or historical agriculture and were correlated with metabolism. Concentrations of inorganic nutrients, PAR, degree-days, suspended solids, and benthic algae were significantly higher in AG streams than in FOR streams. Nutrient and suspended solid concentrations also were higher in REC than in FOR streams,but PAR, degree-days, and benthic algae were similar in REC and FOR streams. GPP varied from <0.1 g O2 m?2 d?1 in FOR streams to 1.0 g O2 m?2 d?1 in AG streams. GPP was similar in REC and FOR streams, suggesting that shading caused by reforestation might reduce GPP to pre-agricultural levels. R24 was 4 to 20+ greater than GPP in all stream types, resulting in highly negative NEP. NEP was less negative in AG streams than in FOR and REC streams. Negative NEP and P/R consistently <1 could have been caused by allochthonous organic matter from remnant forested land (up to 75% forested) in agricultural watersheds. GPP and P/R were strongly correlated with PAR, degree-days, and algal biomass, suggesting that reduced light limited primary production in the streams studied. R24 was positively correlated with nutrient concentrations. Shading caused by reforestation appears to be an important mechanism by which stream metabolism recovers from historical agriculture. Our results provide support for stream restoration efforts focused on developing and maintaining streamside forests.

Meyer, J.L., D.L. Strayer, J.B. Wallace, S.L. Eggert, G.S. Helfman, and N.E. Leonard. 2007. The Contribution of Headwater Streams to Biodiversity in River Networks. Journal of the American Water Resources Association (JAWRA). 43(1): 86-103.

Abstract
The diversity of life in headwater streams (intermittent, first and second order) contributes to the biodiversity of a river system and its riparian network. Small streams differ widely in physical, chemical, and biotic attributes, thus providing habitats for a range of unique species. Headwater species include permanent residents as well as migrants that travel to headwaters at particular seasons or life stages. Movement by migrants links headwaters with downstream and terrestrial ecosystems, as do exports such as emerging and drifting insects. We review the diversity of taxa dependent on headwaters. Exemplifying this diversity are three unmapped headwaters that support over 290 taxa. Even intermittent streams may support rich and distinctive biological communities, in part because of the predictability of dry periods. The influence of headwaters on downstream systems emerges from their attributes that meet unique habitat requirements of residents and migrants by: offering a refuge from temperature and flow extremes, competitors, predators, and introduced species; serving as a source of colonists; providing spawning sites and rearing areas; being a rich source of food; and creating migration corridors throughout the landscape. Degradation and loss of headwaters and their connectivity to ecosystems downstream threaten the biological integrity of entire river networks.

Oleksyn, J., B.D. Kloeppel, S. Lukasiewicz, P. Karolewski, and P.B. Reich. 2007. Ecophysiology of horse chestnut (Aseculus Hippocastanum L.) in degraded and restored urban sites. Polish Journal of Ecology. 55(2): 245-260.

Abstract
We explored changes in growth, phenology, net CO2 assimilation rate, water use efficiency, secondary defense compounds, substrate and foliage nutrient concentration of a degraded urban horse chestnut (Aseculus hippocastanum L.) site restored for three years using mulching (tree branches including foliage) and fertilization (primarily nitrogen addition). Prior to restoration, this site was characterized by high pH (ca.8), low foliage and substrate N, and high Na and C1 concentration. Our data indicated that in untreated plots NaC1 used for road deicing is the decisive factors that may be responsible for the decrease of foliar N concentration (via a reduction in NO3-uptake), for the decrease in photosynthesis (through high concentrations of Na and C1 in the leaves) and for increased senescence of the leaves. After three years of treatment, total nitrogen concentration in substrate increased by 3- to 4- fold and calcium concentration decreased by more than 50% in relation to pretreatment levels. Treatment significantly increased seed production (from less than 12 to more than 100 seeds per tree), individual leaf mass (from 1.8 to 3.3 g/leaf), CO2 assimilation rate (by 21 to 30%), improved leaf C:N ration, and increased foliage life span by as much as six weeks. The beginning of leaf fall in untreated control trees started in mid-July and those of mulched and fertilized trees in late October. Applied treatment also eliminated visible symptoms of leaf damage due to high sodium and chlorine levels, indicating the possible role of other factors in the development of necroses. After three years of treatment, pH of most degraded plots declined from 8.2 to 7.8. That decline was accompanied by an increase in foliar Zn, Cu, and Pb concentration in the mulched and fertilized plants. In addition, treatment lowered foliage phenolics making these plants potentially more vulnerable to insect herbivory. Our study indicates that stable carbon isotope discrimination is of little value as an indicator of cumulative salinity and urban environment stress in A. hippocastanum due to pronounced differences in leaf phenology and ontogeny. The results of our study show that street tree recovery can take as little as two to three years after application of fertilization and mulching.

Pavao-Zuckerman, M.A., and D.C. Coleman. 2007. Urbanization alters the functional composition, but not taxonomic diversity, of the soil nematode community. Applied Soil Ecology. 35(2007): 329-339.

Abstract
We evaluated the response of riparian forest soil nematode community structure to the physico-chemical environment associatedwith urban land use. Soils were sampled seasonally between December 2000 and October 2002 along an urban+rural transect in Asheville, North Carolina.We characterized the taxonomic (to genus) and functional composition (trophic groups) of the nematode community of forest soils, as well as several nematode ecological indicators (maturity index, channel index, weighted faunal index). The diversity of nematode genera was not affected by urban land use. However, there tended to be functional differences in the nematode communities along the land use gradient. The urban soils tended to have lower abundances of predatory and omnivorous nematodes. Differences in channel index scores indicated that there was less fungal dominance in the soil food webs of the urban soils. Our results indicate that the functional composition of the soil food web is an important component of soil biodiversity that can be affected by land use practices. This study was conducted in a relatively small city; hence the influence of pollutants on the soil environment was not as great as in larger cities. Correspondingly, the impact on the soil nematode community was not very severe. The utilization of the nematode community assemblage as an indicator of soil conditions should be further explored in urban places of differing magnitudes of environmental effects.

Petty, J.T., Grossman, G.D. 2007. Size-Dependent Territoriality of Mottled Sculpin in a Southern Appalachian Stream. Transactions of the American Fisheries Society, 136:1750-1761

Abstract
We quantified the space use behaviors of juvenile and adult mottled sculpin Cottus bairdii over a 3-year period in Shope Fork, western North Carolina. Our objectives were to (1) quantify home range size, (2) determine whether the fish exhibit territorial behaviors, (3) characterize the relative stability of territories, and (4) relate temporal variation in behaviors to environmental variability and population size structure. Adult behaviors were consistent with those of a strongly territorial organism. Adults exhibited nonrandom movements, restricted home ranges, and extremely low levels of spatial overlap with neighboring residents (,10% overlap). Territories were established in erosional microhabitats that were significantly more stable (as measured by seasonal shifts in dominant substrate composition) than randomly selected microhabitats in the study site. In contrast to adults, juveniles did not exhibit evidence of territoriality and instead occupied overlapping home ranges (16–36% overlap) in less-stable, depositional microhabitats along the stream margin. Mottled sculpin home range size, home range overlap, and territory abandonment rate were related to the density of large adults rather than flow variability or microhabitat stability. Adult territoriality and juvenile floating provide behavioral mechanisms capable of producing strong regulation of mottled sculpin populations in this system.

Rincon, P.A., M. Bastir, G.D. Grossman. 2007. Form and performance: body shape and prey-capture success in four drift-feeding minnows. Oecologia. 152: 345-355.

Abstract
Identifying links between morphology and performance for ecologically relevant tasks will help elucidate the relationships between organismal design and fitness. We conducted a laboratory study to quantify the relationship between variation in body shape and prey-capture success in four drift-feeding minnow species. We offered drifting prey to individual fish in a test flume, counted successful strikes to measure prey-capture success and recorded the position (X, Y coordinates) of ten landmarks on each fish's outline to delineate the specimen's form. We then quantified shape variation among species and related it to capture performance through thin-plate spline analysis. Our findings demonstrate a strong connection between organismal shape and performance and provide empirical evidence of the cost of morphological specialization for fishes in the drift-feeding functional guild.

Romaniszyn, E.D., J.J. Hutchens Jr., and J.B. Wallace. 2007. Aquatic and terrestrial invertebrate drift in southern Appalachian mountain streams: implications for trout food resources. Freshwater Biology. 52: 1-11.

Abstract
(1) We characterised aquatic and terrestrial invertebrate drift in six south-western North Carolina streams and their implications for trout production. Streams of this region typically have low standing stock and production of trout because of low benthic productivity. However, little is known about the contribution of terrestrial invertebrates entering drift, the factors that affect these inputs (including season, diel period and riparian cover type), or the energetic contribution of drift to trout. (2) Eight sites were sampled in streams with four riparian cover types. Drift samples were collected at sunrise, midday and sunset; and in spring, early summer, late summer and autumn. The importance of drift for trout production was assessed using literature estimates of annual benthic production in the southern Appalachians, ecotrophic coefficients and food conversion efficiencies. (3) Abundance and biomass of terrestrial invertebrate inputs and drifting aquatic larvae were typically highest in spring and early summer. Aquatic larval abundances were greater than terrestrial invertebrates during these seasons and terrestrial invertebrate biomass was greater than aquatic larval biomass in the autumn. Drift rates of aquatic larval abundance and biomass were greatest at sunset. Inputs of terrestrial invertebrate biomass were greater than aquatic larvae at midday. Terrestrial invertebrate abundances were highest in streams with open canopies and streams adjacent to pasture with limited forest canopy. (4) We estimate the combination of benthic invertebrate production and terrestrial invertebrate inputs can support 3.3-18.2 g (wet weight) m?2 year?1 of trout, which is generally lower than values considered productive [10.0-30.0 g (wet weight) m?2 year?1]. (5) Our results indicate terrestrial invertebrates can be an important energy source for trout in these streams, but trout production is still low. Any management activities that attempt to increase trout production should assess trout food resources and ensure their availability.

Skyfield JP, and GD Grossman. 2007. Microhabitat use, movements and abundance of gilt darters (Percina evides) in southern Appalachian (USA) streams. Ecol Freshwater Fish 17: 219 – 230

Abstract
We examined microhabitat use by gilt darters (Percina evides) in two streams in the south-eastern USA.

Velbel, M. A. and J. R. Price. 2007. Solute geochemical mass-balances and mineral weathering rates in small watersheds: Methodology, recent advances, and future directions. Applied Geochemistry, 22: 1682-1700.

Abstract
Solute-based geochemical mass balance methods are commonly used in small-watershed studies to estimate rates of a variety of geochemical processes at the Earth’s surface, including primary-mineral weathering and soil formation, and the quantitative contribution of these elemental transfer processes to cation budgets, nutrient cycling, and landscape susceptibility to acid deposition. Weathering rates of individual minerals in watershed mass-balance studies are determined by solving a system of simultaneous linear geochemical mass-balance equations with constant (stoichiometric) coefficients. These equations relate the measured net fluxes to the (known) stoichiometries and (unknown) rates of weathering reactions for multiple minerals in the weathering profiles. Solving the system of equations requires petrologic, mineralogic, hydrologic,botanical, and aqueous geochemical data. The number of mineral-weathering rates that can be determined is limited by the number of elements for which solute mass-balance equations can be written. In addition to calculating mineral weathering rates, elemental transfer into or out of the biomass may also be calculated. Elemental uptake by aggrading forest vegetation can act as an intrawatershed sink for at least some mineral-derived cations, producing mineral weathering rates higher than would be estimated from solute fluxes alone; similarly, element release from decaying forest biomass can result in higher solute fluxes than are produced by weathering alone. The mathematics of, significant contributions from, role of biomass in, and recent advances in, watershed geochemical mass-balance methods are discussed using examples from the Appalachian headwaters watersheds of the Coweeta Hydrologic Laboratory in the southern Blue Ridge Physiographic Province of North Carolina, USA.

Vose, J.M., and P.V. Bolstad. 2007. Biotic and abiotic factors regulating forest floor CO2 flux across a range of forest age classes in the southern Appalachians. Pedobiologia. 50: 577-587.

Abstract
We measured forest floor CO2 flux in three age classes of forest in the southern Appalachians: 20-year old, 85-year old, and old-growth. Our objectives were to quantify differences in forest floor CO2 flux among age classes, and determine the relative importance of abiotic and biotic driving variables. Forest floor CO2 flux was measured using an openflow infrared gas analyzer measurement system for 24 h periods and samples were taken every 2 months over a 2-year period. Litter/soil interface, soil temperature (5 cm depth), soil moisture (%), forest floor moisture (%), forest floor mass, fine root (< 2 mm) mass, coarse root mass (> 2 mm), forest floor C and N (%), fine root C and N, coarse root C and N, and soil N and C were co-measured during each sample. Results showed significant nonlinear relationships (r2 = 0.68 to 0.81) between litter/soil interface temperature and forest floor CO2 flux for all three forest age classes, but no differences in temperature response parameters. These results indicated no differences in forest floor CO2 flux among age classes. Considerable temporal variation in abiotic and biotic variables was observed within and among forests. Biotic variables correlated with forest floor CO2 flux included indices of litter and root quality. Differences in biotic variables correlated with forest floor CO2 flux among forests may have been related to shifts in the relative importance of heterotrophic and autotrophic respiration components to overall forest floor CO2 flux.

Webster, J.R. 2007. Spiraling down the river continuum: stream ecology and the U-shaped curve. Journal of the North American Benthological Society. 26(3): 375-389.

Abstract
The spiraling concept provides an explicit approach to modeling the longitudinal linkages within a river continuum. I developed a spiraling-based model for particulate organic C dynamics in the Little Tennessee River to synthesize existing data and to illustrate our current understanding of ecosystem processes in river ecosystems. The Little Tennessee River is a medium-sized river flowing ~100 km through the southern Appalachian Mountains of northern Georgia and western North Carolina (USA). Across this distance, allochthonous inputs decrease and autochthonous production increases, resulting in a U-shaped curve of energy input. The model was set up as an advecting seston compartment interacting with 3 benthic compartments: coarse benthic organic matter, fine benthic organic matter,and autotrophs. Model-estimated ecosystem respiration was consistently lower than measured values, suggesting a need to evaluate our measurements of whole-stream metabolism. Also, model-predicted seston concentrations were generally lower than measured values, reflecting a need to consider additional sources of organic C in the model. For the whole river system, leaves accounted for 19% of inputs, primarily near the headwaters, and the remaining input was from instream primary production in the lower reaches of the river. Almost 1/2 of the input was respired, 28% by autotrophic respiration and 21% by heterotrophic respiration, and the remaining 51% was transported downstream. Ecosystem efficiency was ~50% along the length of the river, and turnover length increased from several hundred meters at the headwaters to >100 km downstream. Based on various measures, the transition from heterotrophy to autotrophy ranged from 25 to >100 km downstream from the headwaters. As this model illustrates, a consequence of downstream transport is that much of the particulate C in streams is metabolized a considerable distance downstream from where it enters the stream. This longitudinal linkage is essential to our understanding of stream ecosystems.

Whitaker, D.M., D.F. Stauffer, G.W. Norman, P.K. Devers, J. Edwards, W.M. Giuliano, C. Harper, W. Igo, J. Sole, H. Spiker, and B. Tefft. 2007. Factors associated with variation in home-range size of Appalachian Ruffed Grouse (Bonasa Umbellus). The Auk. 12

Abstract
From 1996 to 2001, researchers at 10 Appalachian study sites collected radiotracking data sufficient to delineate 1,054 seasonal home ranges of Ruffed Grouse (Bonasa umbellus; hereafter "grouse").

Wurzburger, N., and R.L. Hendrick. 2007. Rhododendron thickets alter N cycling and soil extracellular enzyme activities in southern Appalachian hardwood forests. Pedobiologia. 50: 563-576.

Abstract
Rhododendron maximum L., a spreading understory shrub, inhibits overstory regeneration and alters forest community structure in southern Appalachian hardwood forests. Using paired plots and reciprocal litter transplants in forests with and without R. maximum cover, we examined the influence of R. maximum on litter mass and quality, N cycling and soil extracellular enzymes. Standing stocks of soil organic matter, soil N, leaf litter mass and fine root biomass were greater in forests with R. maximum than those without. Tannin extracts from R. maximum foliage, and leaf litter and fine roots collected under R. maximum had a relatively high capacity to precipitate protein compared to extracts from trees. Across the growing season, soil inorganic N availability was generally lower under R. maximum, mostly due to reduced NO3- availability. Our data suggest that R. maximum litter alters N cycling through the formation of recalcitrant polyphenol-organic N complexes. Soil extracellular enzymes indicate the potential processing rates of organic substrates. Between forest types, polyphenol oxidase activity was greatest in R. maximum O horizons, regardless of litter type, suggesting that the local microbial community can better degrade and access protein-tannin-complexed N. Protease activity did not differ between forest types, but was greater on R. maximum leaf litter than hardwood leaf litter. The alteration of the N cycle via the formation of polyphenol-organic N complexes may contribute to hardwood seedling suppression, while the enzymatic release of these complexes by ericoid mycorrhizal fungi may increase N acquisition for R. maximum and contribute to its expansion in southern Appalachian forests.

Addington, R.N., L.A. Donovan, R.J. Mitchell, J.M. Vose, S.D. Pecot, S.B. Jack, U.G. Hacke, J.S. Sperry, and R. Oren. 2006. Adjustments in hydraulic architecture of Pinus palustris maintain similar stomatal conductance in xeric and mesic habitats. Plant Cell and Environment. 29(4): 535-545.

Abstract
We investigated relationships between whole-tree hydraulic architecture and stomatal conductance in Pinus palustris Mill. (longleaf pine) across habitats that differed in soil properties and habitat structure. Trees occupying a xeric habitat (characterized by sandy, well-drained soils, higher nitrogen availability and lower overstory tree density) were shorter in stature and had lower sapwood-to-leaf area ratio (AS:AL) than trees in a mesic habitat. The soil-leaf water potential gradient (?S v ?L) and leaf-specific hydraulic conductance (?S) of roots. Leaf and canopy stomatal conductance (gs and Gs, respectively) were also similar between sites, and they tended to be somewhat higher at the xeric site during morning hours when vapour pressure deficit (D) was low A hydraulic model incorporating tree height, AS:AL and ?S v ?L accurately described the observed variation in individual tree GSref (GS at D = 1kPa) across sites and indicated that tree height was an important determinant of GSref across sites. This, combined with a 42% higher root-to-leaf area ratio (AR:AL) at the xeric site, suggests that xeric site trees are hydraulically well equipped to realize equal v and sometimes higher v potential for conductance compared with trees on mesic sites. However, a slightly more sensitive stomatal closure response to increasing D observed in xeric site trees suggests the potential for higher conductance many only be reached when D is low and when the capacity of the hydraulic system to supply water to foliage is not greatly challenged.

Ardon, M., Pringle, C.M., Eggert, S.L. 2009. Does leaf chemistry differentially affect breakdown in tropical vs temperate streams? Importance of standardized analytical techniques to measure leaf chemistry. North American Benthological Society, 28(2):440-

Abstract
Comparisons of the effects of leaf litter chemistry on leaf breakdown rates in tropical vs temperate streams are hindered by incompatibility among studies and across sites of analytical methods used to measure leaf chemistry. We used standardized analytical techniques to measure chemistry and breakdown rate of leaves from common riparian tree species at 2 sites, 1 tropical and 1 temperate, where a relatively large amount of information is available on litter chemistry and breakdown rates in streams (La Selva Biological Station, Costa Rica, and Coweeta Hydrologic Laboratory, North Carolina, USA). We selected 8 common riparian tree species from La Selva and 7 from Coweeta that spanned the range of chemistries of leaf litter naturally entering streams at each site. We predicted that concentrations of secondary compounds would be higher in the tropical species than in the temperate species and that high concentrations of condensed tannins would decrease breakdown rates in both sites. Contrary to our predictions, mean concentration of condensed tannins was significantly greater (2.63, p , 0.001) for species at Coweeta than for species at La Selva. Concentration of condensed tannins was negatively correlated with breakdown rate among Coweeta species (r=-0.80), not among La Selva species, and negatively correlated when the 2 sites were combined (r=-0.53). Concentrations of structural compounds were strongly correlated with breakdown rate at both sites (Coweeta species, lignin r=-0.94, cellulose r=-0.77; La Selva species, cellulose r=-0.78, C r=-0.73). The chemistries of 8 riparian species from La Selva and 7 riparian species from Coweeta were not as different as expected. Our results underline the importance of standardized analytical techniques when making cross-site comparisons of leaf chemistry.

Burcher, C.L., and E.F. Benfield. 2006. Physical and biological responses of streams to suburbanization of historically agriculture watersheds. Journal of the North American Benthological Society. 25(2): 356-369.

Abstract
We investigated whether suburbanization influenced the physical and biological characteristics of ten 3rd-or 4th-order streams that drain historically agricultural watersheds in the southern Appalachians near Asheville, North Carolina. Five watersheds had areas of recent suburban development proximal to stream sites, and 5 watersheds were not currently undergoing suburban development. We estimated 5 hydrological, 10 geomorphological, 6 erosional, and 3 depositional (i.e., substrate) variables, and 13 fish and 8 macroinvertebrate metrics in the study sites. We used Student¼s t-tests and multivariate analysis of variance to compare the 45 variables between sites in agricultural and suburban watersheds. We used Detrended Correspondence Analysis (DCA) to detect subtle differences in taxonomic composition and abundance among watersheds. Stormflow total suspended solids were significantly lower and substrate inorganic matter content was significantly higher in streams influenced by suburban development. Fish taxa richness and the density of nonguarding fishes were significantly higher in sites in suburban watersheds than in sites in agricultural watersheds. No other fish or macroinvertebrate metric differed with respect to watershed land use, but ordination of sites by fish and macroinvertebrate species abundance suggested that biotic assemblages at sites in suburban watersheds were distinct from those at sites in agricultural watersheds. Therefore, some taxa may have been influenced by suburban development. Our results suggest that watershed hydrology, sediment delivery, and sediment composition might be important factors influencing biota in streams draining agricultural vs suburban watersheds. Biological assemblages in streams differed structurally with respect to watershed land use, but streams did not appear to be otherwise influenced by suburban development. We conclude that suburbanization near historically agricultural southern Appalachian streams induces subtle changes to inorganic sediment dynamics, substrate composition, and fish and macroinvertebrate assemblage structure.

Clinton, B.D., and J.M. Vose. 2006. Variation in stream water quality in an urban headwater stream in the southern Appalachians. Water, Air, and Soil Pollution. 169: 331-353.

Abstract
We examined the influence of a forested landscape on the quality of water in a stream originating on an urban landscape and flowing through National Forest lands. Sample sites included an urban stream (URB), a site on the same stream but within a National Forest (FOR) and 2 km downstream from the URB site, and a small, undisturbed, forested reference tributary of the main stream (REF). We monitored stream water quality from March 2002 through June 2003. Average base flows for the three stream sites were URB = 184 L s?1, FOR = 420 L s?1, and REF = 17 L s?1. We analyzed weekly stream water samples for NO?3 , NH+4 , PO+4 , Cl?, K, Ca, Mg, SO4, SiO2, pH, conductivity, total suspended solids (TSS), and bacteria on a monthly basis. Most solutes were higher in concentration at the URB site, as were conductivity, TSS, and bacteria counts. Reductions in NO?3 , NH+4 , and PO+4 concentrations between the URB and FOR sites were inferred from changes in nutrient: chloride ratios. Bacteria populations were greater and more responsive to stream temperature at the URB site. Water quality responses to changes in stream discharge varied among sites but were greater at the URB site. By all measures, water quality was consistently higher at the FOR site than at the URB site.

Coombs, S., and G.D. Grossman. 2006. Mechanosensory based orienting behaviors in fluvial and lacustrine populations of mottled sculpin (Cottus bairdi). Marine and Freshwater Behaviour and Physiology. 39(2): 113-130.

Abstract
We compared prey-orienting and rheotactic behaviors in a fluvial (Coweeta Creek) and lacustrine (Lake Michigan) population of mottled sculpin. Blinded sculpin from both populations exhibited unconditioned, mechanosensory based rheotaxis to low velocity flows. Whereas Lake Michigan sculpin generally showed increasing levels of positive rheotaxis to increasing velocities, Coweeta Creek sculpin show varying levels of positive rheotaxis at low to intermediate velocities and often reduced positive rheotaxis or even negative rheotaxis at the highest velocities (12 cm s-1). Blinded Lake Michigan, but not Coweeta Creek mottled sculpin exhibited an orienting response to a small (3mm diameter) artificial prey (50 Hz vibrating sphere). In conclusion, the two populations differed in the strength and polarity of the rheotactic response at higher velocities and in their responsiveness to mechanosensory cues from epibenthic prey sources. These behavioral differences have most likely arisen from different learning experiences in different habitats and from the greater importance of visual cues to the Coweeta Creek mottled sculpin and mechanosensory cues to Lake Michigan mottled sculpin in the sensory guidance of orienting behaviors.

Cross, W.F., J.B. Wallace, A.D. Rosemond, and S.L. Eggert. 2006. Whole-system nutrient enrichment increases secondary production in a detritus-based ecosystem. Ecology. 87(6): 1556-1565.

Abstract
Although the effects of nutrient enrichment on consumervresource dynamics are relatively well studied in ecosystems based on living plants, little is known about the manner in which enrichment influences the dynamics and productivity of consumers and resources in detritus-based ecosystems. Because nutrients can stimulate loss of carbon at the base of detrital food webs, effects on higher consumers may be fundamentally different than what is expected for living-plant-based food webs in which nutrients typically increase basal carbon. We experimentally enriched a detritus-based headwater stream for two years to examine the effects of nutrient-induced changes at the base of the food web on higher metazoan (predominantly invertebrate) consumers. Our paired catchment design was aimed at quantifying organic matter and invertebrate dynamics in the enriched stream and an adjacent reference stream for two years prior to enrichment and two years during enrichment. Enrichment had a strong negative effect on standing crop of leaf litter, but no apparent effect on that of fine benthic organic matter. Despite large nutrient-induced reductions in the quantity of leaf litter, invertebrate secondary production during the enrichment was the highest ever reported for headwater streams at this Long Term Ecological Research site and was 1.2v3.3 times higher than predicted based on 15 years of data from these streams. Abundance, biomass, and secondary production of invertebrate consumers increased significantly in response to enrichment, and the response was greater among taxa with larval life spans _1 yr than among those with larval life spans .1 yr. Production of invertebrate predators closely tracked the increased production of their prey. The response of invertebrates was largely habitat-specific with little effect of enrichment on food webs inhabiting bedrock outcrops. Our results demonstrate that positive nutrient-induced changes to food quality likely override negative changes to food quantity for consumers during the initial years of enrichment of detritus-based stream ecosystems. Longer-term enrichment may impact consumers through eventual reductions in the quantity of detritus.

Earl, S.R., H.M. Valett, and J.R. Webster. 2006. Nitrogen saturation in stream ecosystems. Ecology. 87(12): 3140-3151.

Abstract
The concept of nitrogen (N) saturation has organized the assessment of N loading in terrestrial ecosystems. Here we extended the concept to lotic ecosystems by coupling Michaelis-Menten kinetics and nutrient spiraling. We propose a series of saturation response types, which may be used to characterize the proximity of streams to N saturation. We conducted a series of short-term N releases using a tracer (15 NO3-N) to measure uptake. Experiments were conducted in streams spanning a gradient of background N concentration. Uptake increased in four of six streams as NO3-N was incrementally elevated, indicating that these streams were not saturated. Uptake generally corresponded to Michaelis-Menton kinetics but deviated from the model in two streams where some other growth-critical factor may have been limiting. Proximity to saturation was correlated to background N concentration but was better predicted by the ratio of dissolved inorganic N (DIN) to soluble reactive phosphorus (SRP), suggesting phosphorus limitation in several high-N streams. Uptake velocity, a reflection of uptake efficiency, declined nonlinearly with increasing N amendment in all streams. At the time, uptake velocity was highest in the low vN streams. Our conceptual model of N transport, uptake, and uptake efficiency suggests that, while streams may be active sites of N uptake on the landscape, N saturation contributes to nonlinear changes in stream N dynamics that correspond to decreased uptake efficiency.

Fraterrigo, J.M., M.G. Turner, and S.M. Pearson. 2006. Interactions between past land use, life-history traits and understory spatial heterogeneity. In Landscape Ecology. 21: 777-790.

Abstract
Past land use has contributed to variability in the distribution of herbaceous species by reducing plant abundance and altering species¼ chances of recolonizing suitable habitat. Land use may also influence plant heterogeneity by changing environmental conditions within stands. We compared the variability of understory herb abundance in southern Appalachian forests with different land-use histories to examine how past land use influenced plant heterogeneity. The cover of eleven focal species or genera was estimated and mineral soil concentrations were determined during 2001 and 2002 in eight stands that were farmed, logged, or had no disturbance history (reference) in western North Carolina. Analysis of the coefficients of variation revealed that the abundance of understory plants was more heterogeneous in disturbed stands compared with reference stands. However, when nutrient availability differences were accounted for by detrending the plant cover data, understory variability within stands declined, and no differences between disturbed and reference stands could be distinguished. This finding suggests that nutrient availability has important effects on plant heterogeneity, which depend on past land use. Species dispersal, seed size, and phenology also explained variability in the spatial heterogeneity of plants, but generally only before soil nutrient differences were statistically controlled. In addition to demonstrating that past land use has longterm effects on plant heterogeneity, these results indicate that soil nutrients may play different roles in determining vegetation patterns in historically altered and unaltered forests.

Fraterrigo, J.M., M.G. Turner, and S.M. Pearson. 2006. Previous land use alters plant allocation and growth in forest herbs. Journal of Ecology. 94: 548-557.

Abstract
(1) Former human practices can persistently influence forest ecosystems, particularly by altering the distribution and abundance of vegetation. Previous research has focused on the role of colonization success in governing plant community patterns in abandoned forests, but few studies have explored how changes in the performance of adult plants may contribute to changes in plant populations. (2) We examined patterns of biomass allocation and growth of 12 herbaceous plant species in southern Appalachian forest stands that have developed after agricultural abandonment or logging at least 55 years ago, to determine whether plant performance varied with land-use history. Soil nutrient availability and canopy closure were also investigated. (3) Adult plant biomass allocation varied appreciably among stands with different histories. Herbs in farmed stands generally allocated the most to leaves and the least to stems, while reference stands showed the opposite pattern. Plants in previously farmed sites had the highest rate of growth, although we observed considerable interspecific variation in plant performance. Stem allocation and relative growth rate were positively correlated in reference stands, but not in farmed or logged stands. Similarly, the growth of plants was clearly associated with soil nutrient concentration in reference stands but not in farmed or logged stands. (4) Differences in understorey density and soil nutrient availability may account for the observed patterns. Total herbaceous cover was appreciably lower in farmed and logged stands (58% and 51%) than in reference stands (78%), and soil phosphorus was higher in farmed stands than in logged and reference stands. Thus, competition for light and nutrients may be lower in farmed and logged stands than in reference stands, despite there being no difference in canopy closure with land-use history. (5) Overall, these results suggest that land-use history may influence environmental variables in ways that can enhance the performance of some herbaceous species. However, not all species may respond similarly to these changes.

Fraterrigo, J.M., T.C. Balser, and M.G. Turner. 2006. Microbial community variation and its relationship with nitrogen mineralization in historically altered forests. Ecology. 87(3): 570-579.

Abstract
Past land use can impart soil legacies that have important implications for ecosystem function. Although these legacies have been linked with microbially mediated processes, little is know about the long-term influence of land use on soil microbial communities themselves. We examined whether historical land use affected soil microbial community composition (lipid profiles) and whether community composition was related to potential net nitrogen (N) mineralization rates in southern Appalachian (USA) forest stands abandoned from agriculture or logging and reforested > 50 yr ago. Microbial community composition was determined by a hybrid procedure of phospholipid fatty acid (PLFA) and fatty acid methyl ester (FAME) analysis. We found that community composition varied significantly with past land use. Communities in formerly farmed stands had a higher relative abundance of markers for gram-negative bacteria and a lower abundance of markers for fungi compared with previously logged and reference (i.e., no disturbance history) stands. Potential net N mineralization rates were negatively correlated with fungal and gram-negative bacterial markers in both farmed and reference stands, and fungal abundance and soil bulk density effectively predicted mineralization rates in all stands. Our results indicate that the alteration of microbial communities by historical land use may influence the ecosystem processes they mediate. This is in contrast to typical expectations about microbial community resilience to change. Here, the decrease in fungal abundance observed from disturbance appeared to result in decreased nitrogen mineralization over the long term.

Giladi, I. 2006. Choosing benefits or partners: a review of the evidence for the evolution of myroecochory. Oikos. 112: 481-492.

Abstract
Myrmecochory, or seed dispersal by ants, is a dispersal syndrome found among several thousand plant species occupying different ecosystems and geographical regions. Typically, ants benefit from consuming a lipid-rich appendage on the seed and in return provide seed dispersal service to the plant. Several hypotheses have been proposed to explain the selective advantage for plants resulting from myrmecochory, including directed dispersal, dispersal for distance and escape from seed predators. I contrast the evidence available in the literature for these hypotheses and distinguish the studies on the basis of ecosystem and plant growth forms. The predator-avoidance and the distance dispersal hypotheses were supported in most studies that addressed them, and the directed dispersal hypothesis was supported in about half of the studies that tested it. Multiple hypotheses were supported in most studies that tested more than one hypothesis, suggesting that the various selective advantages conferred from myrmecochory are seldom exclusive. I also review evidence for the hypothesis that plants have evolved adaptations both for selecting seed dispersers and for manipulating the behavior of those dispersers. Based on this evidence, I argue that focusing future research on the evolution of partner choice by myrmecochores and its effects on the overall plant fitness will be more fruitful than putting an emphasis on classifying the selective advantage to plants into distinct categories and test for their existence separately.

Gragson, T.L., and P.V. Bolstad. 2006. Land use legacies and the future of southern Appalachia. Society and Natural Resources. 19: 175-190.

Abstract
Southern Appalachian forests have apparently recovered from extractive land use practices during the 19th and 20th centuries, yet the legacy of this use endures in terrestrial and aquatic systems of the region. The focus on shallow time or the telling of stories about the past circumscribes the ability to anticipate the most likely outcomes of the trajectory of change forecast for the Southeast as the ¬¬Old South¼¼ continues its transformation into the ¬¬New South.¼¼ We review land use research of the Coweeta Long Term Ecological Research (LTER) project that addresses the nature and extent of past and present human land use, how land use has affected the structure and function of terrestrial and aquatic communities, and the forces guiding the anticipated trajectory of change. Unlike development in the western or northeastern regions of the United States, the southeastern region has few practical, political, or geographical boundaries to the urban sprawl that is now developing.

Gragson, Ted L., and M. Grove. 2006. Social science in the context of the long term ecological research program. Society and Natural Resources. 19: 93-100.

Abstract
This special issue of Society and Natural Resources brings the results of long-term ecological research with an explicit social dimension to the attention of the social scientific research community. Contributions are from the Baltimore Ecosystem Study LTER, the Central Arizona-Phoenix LTER, the Coweeta LTER and the Northern Temperate Lakes LTER. The range of practice represented at these four sites serves to identify commonalities and differences in the results as well as the experience of integrative research. The objective of this special issue is to extend a call to social scientists of all kinds to engage with the LTER program in long-term research and synthesis to help answer the urgent and intriguing questions of our day.

Grossman, G.D., R.E. Ratajczak Jr., J.T. Petty, M.D. Hunter, J.T. Peterson, and G. Grenouillet. 2006. Population dynamics of mottled sculpin (pisces) in variable environment: information theoretic approaches. Ecological Monographs. 76(2): 217-234.

Abstract
We used strong inference with Akaike¼s Information Criterion (AIC) to assess the processes capable of explaining long-term (1984v1995) variation in the per capita rate of change of mottled sculpin (Cottus bairdi) populations in the Coweeta Creek drainage (USA). We sampled two fourth- and one fifth-order sites (BCA [uppermost], BCB, and CC [lowermost]) along a downstream gradient, and the study encompassed extensive flow variation. Physical habitat availability varied significantly both within and among the sites. Sculpin densities in all sites were highly stable (coefficients of variation 5 0.23 0.41) and sampling variability was low (coefficients of variation 5 0.11v0.15). Population stability was positively associated with habitat stability, and the only significant correlations of population parameters among sites involved juveniles. Sculpin densities were significantly higher in BCB than in CC. The data suggest that, despite their proximity, the dynamics of populations within the sites are being determined by small scale (i.e., 30v50 m) rather than broad-scale spatial processes. Both AIC and Dennis and Taper analyses indicated that simple density dependence had the greatest ability to explain variation in r for all life-history classes in all sites (AIC, seven of nine cases; Dennis and Taper, nine of nine cases). Multiprocess models had little explanatory power. When adults were removed from two sites, juvenile sculpin shifted into microhabitats formerly occupied by adults. No shifts occurred in control sites. Consequently, it is likely that the patterns of density dependence observed in all three sites were a consequence of intraspecific competition for space. Our findings argue for a multitiered approach to the study of population variation, one that encompasses long-term monitoring, spatial variation, and experimental testing of potential mechanisms.

Hagen, E.M., J.R. Webster, and E.F. Benfield. 2006. Are leaf breakdown rates a useful measure of stream integrity along an agricultural landuse gradient? Journal of the North American Benthological Society. 25(2): 330-343.

Abstract
Biological indicators often are used to assess and manage water quality in anthropogenically altered stream systems. Leaf breakdown has the potential to be a good indicator of stream integrity because it integrates a variety of biological, chemical, and physical conditions. Red maple (Acer rubrum L.) leaf breakdown rates were measured along a gradient of agricultural land use in southern Appalachian streams to assess the use of leaf breakdown rates as a measure of stream integrity. Landuse categories included forested, light agriculture, moderate agriculture, and heavy agriculture. Leaf breakdown rates were related to landuse category but did not differ significantly among landuse categories. Nutrient concentration, temperature, and sedimentation increased, and dissolved O2 decreased along the landuse gradient from forest to heavy agriculture. Macroinvertebrate richness, macroinvertebrate density, and shredder density were the only significant predictors of leaf breakdown rates. We conclude that leaf breakdown rates may not be a useful indicator of stream integrity because of the confounding effects that agricultural land use has on breakdown rates.

Henning, J.G., and P.J. Radtke. 2006. Ground-based Laser Imaging for Assessing Three-dimensional Forest Canopy Structure. Photogrammetric Engineering and Remote Sensing: 1349-58.

Abstract
Improved understanding of the role of forests in carbon, nutrient, and water cycling can be facilitated with improved assessments of canopy structue, better linking leaf-level processes to canopy structure and forest growth. We examined the use of high-resolution, ground-based laser imaging for the spatially explicit assessment of forest canopies. Multiple range images were obtained and aligned during both leaf-off and leaf-on conditions on a 20m x 40m plot. The plot location was within a mixed broadleaved deciduous forest in western North Carolina. Digital terrain and canopy height models were created for a 0.25m square grid. Horizontal, vertical, and three-dimensional distributions of plant area index, created using gap-fraction based estimation, had 0.5m resolution for a cubic lattice. Individual tree measurements, including tree positions and diameter at breast height, were made from the scanner data with positions, on average, within 0.43m and diameters within 5cm of independent measurements, respectively. Our methods and results confirm that applications of ground-based laser scanning provide high-resolution, spatially-explicit measures of plot-level forest canopy structure.

Johnson, B.R., Wallace, J.B., Rosemond, A.D., Cross, W.F. 2006. Larval salamander growth responds to enrichment of a nutrient poor headwater stream. Hydrobiologia, 573: 227-232.

Abstract
While many studies have measured effects of nutrient enrichment on higher trophic levels in grazing food webs, few such studies exist for detritus-based systems. We measured effects of nitrogen and phosphorus addition on growth of larval Eurycea wilderae in a heterotrophic headwater stream using a repeated markrecapture design. Growth estimates for 208 recaptured larvae (control stream n = 92; treatment stream n = 116) resulted in a growth rate of 0.0027 d-1 in each stream prior to enrichment, whereas during enrichment treatment growth rates (g = 0.0069 d-1 [±0.0019, 95% C.I.]) were significantly higher than control (g = 0.0043 d-1 [±0.0007, 95% C.I.]). Results indicate that E. wilderae growth is tightly linked to the detrital resource and that growth may be indirectly affected by both quantity and quality of detritus. This study provides some of the first evidence that nutrient enrichment of detritus-based systems can influence multiple trophic levels in ways similar to autotrophic systems.

Lei, T.T., E.T. Nilsen, and S.W. Semones. 2006. Light environment under Rhododendron maximum thickets and estimated carbon gain of regenerating forest tree seedlings. Plant Ecology. 184: 143-156.

Abstract
Canopy tree recruitment is inhibited by evergreen shrubs in many forests. In the southern Appalachian mountains of the USA, thickets of Rhododendron maximum L. restrict dominant canopy tree seedling survival and persistence. Using R. maximum as a model system, we examined available light under the thickets and the photosynthetic responses of seedlings of canopy tree species. We tested the hypothesis that the additional shading from under R. maximum drives carbon gain in seedlings below the threshold for growth and survival. A reduction in light under the thicket was found where canopy openness (derived from canopy photographs) under R. maximum was half the amount measured in forest without R. maximum. R. maximum also reduced direct radiation by 50% and diffuse radiation by 12-29% compared to forest without the shrub layer. Mean mid-day PPFD (photosynthetically active photon flux density between 1000 and 1400 h) under R. maximum (obtained from quantum sensors was below 10 +mol m-2 s-1 on both clear and overcast days and the amount of sun flecks greater than 10 +mol m-2 s-1 PPFD was only 0-20 min per day. In contrast, forest without R. maximum received a mean PPFD of 18-25 +mol m-2 s-1 on clear days and a cumulative sun fleck duration of 100-220 min per day in all sky conditions. Consistent with light availability between the sites, daily carbon gain in Quercus rubra L. seedlings was lower in forest with R. maximum compared to forest where the shrub was absent. The presence of the shrub layer also significantly suppressed average mid-day photosynthesis of both Q rubra and Prunus serotina Ehrt. seedlings on 8 out of 11 measurement dates. However, parameters derived from light response curves between seedlings growing in forest sites with or without a thicket of R. maximum was significantly different only in Amax (maximum photosynthetic rate), indicating a lack of further acclimation to the deeper shade under R. maximum. While the additional shade cast by R. maximum is sufficient to prevent the regeneration of tree seedlings under this shrub, there was sufficient heterogeneity in light under the thicket to imply that deep shade only partially explains the complete inhibition of regenerating canopy trees under R. maximum.

Leigh, D.S., and P.A. Webb. 2006. Holocene erosion, sedimentation, and stratigraphy at Raven Fork,Southern Blue Ridge Mountains, USA. Geomorphology. 78: 161-177.

Abstract
Holocene colluvial and alluvial stratigraphy and a radiocarbon chronology are presented for the valley of the lower three kilometers of Raven Fork, a mountain stream draining 194 km2 of high relief (1.3 km) terrain of the Southern Blue Ridge Mountains in western North Carolina, USA, which is in a region that lacks good chronological data. Lower hillslopes, alluvial/ colluvial fans, alluvial bottomlands (first terrace and floodplain), and the modern stream channel are landforms described with respect to soils, stratigraphy, and sedimentary structures. Standard methods for subsurface investigations (core holes, excavation units, exposures) are used in conjunction with extensive archeological excavations and cultural chronologies. Radiocarbon ages from each landform are used to calculate long-term-average rates of sedimentation. Results indicate that the first half of the Holocene experienced somewhat more rapid rates of hillslope sedimentation (0.3 to 1.1 mm/yr) than the last half of the Holocene (0.1v0.2 mm/yr) on footslopes, toeslopes, and alluvial/colluvial fans prior to historic time. We suggest that these subtle differences in the rates of sedimentation were driven by changes in global paleoclimate that favored a high frequency of heavy rainfall, including tropical storms and/or severe thunderstorms and more (and possibly larger) floods during the first half of the Holocene. Prehistoric rates of vertical accretion on the first terrace (T1) ranged from 0.1 to 0.8 mm/yr between about 10,000 and 3000 calendar years ago, and incision below T1 formed the late Holocene floodplain beginning at about 6000 years ago. We suggest that this incision is linked to a reduction in the supply of sediment and a reduction in the magnitude of floods. Historical rates of sedimentation on all parts of the depositional landscape (2.0v2.7 mm/yr on hillslopes and fans and 5.8v6.5 mm/yr on floodplains) were about an order of magnitude greater than prehistoric rates. We attribute these rates to human impacts, such as timber harvest and land clearing, which caused accelerated erosion. We attribute the abundance of fine-grained sediment in streams of the Southern Blue Ridge province, which is atypical in many mountain streams around the world, to the regionally widespread mantle of saprolite as a source of sediment to the fluvial system. Holocene sedimentation on all depositional landforms in the valley led to sedimentary burial of archeological materials, which highlights the need to consider site burial on lower hillslopes and terraces for evaluation of the cultural resources in the Southern Blue Ridge Mountains. These findings show that the entrenched condition of the Raven Fork channel was inherited from the middle Holocene and can be considered a (natural  state for this mountain stream, casting doubt on the negative connotation that is often assigned to entrenched channels.

Maier, C.A., and B.D. Clinton. 2006. Relationship between stem CO2 efflux, stem sap velocity and xylem CO2 concentration in young loblolly pine trees. Plant, Cell and Environment. 29: 1471-1483.

Abstract
We measured diel patterns of stem surface CO2 efflux (Es, +mol m-2s-1), sap velocity (vs, mm s-1) and xylem CO2 concentration ([CO2]) (Xs, %) in 8-year-old loblolly pine trees during the spring to determine how vs and Xs influence Es. All trees showed a strong diel hysteresis between Es and stem temperature, where at a given temperature, Es was lower during the day than at night. Diel variations in temperature-independent Es were correlated with vs (R2=0.54), such that at maximum vs, Es was reduced between 18 and 40%. However, this correlation may not represent a cause-and-effect relationship. In a subset of trees, vs was artificially reduced by progressively removing the tree canopy. Reducing vs to near zero had no effect on Es and did not change the diel hysteretic response to temperature. Diel Xs tended to decrease with vs and increase with Es, however, in defoliated trees, large increases in Xs, when vs+0, had no effect on Es. We conclude that at this time of the year, Es is driven primarily by respiration of cambium and phloem tissues and that sap flow and xylem transport of CO2 had no direct influence on Es.

Price, K., and D.S. Leigh. 2006. Comparative water quality of lightly- and moderately-impacted streams in the southern Blue Ridge Mountains, USA. Environmental Monitoring and Assessment. 120: 269-300.

Abstract
For less-developed regions like the Blue Ridge Mountains, data are limited that link basin-scale land use with stream quality. Two pairs of lightly impacted (90-100% forested) and moderately impacted (70-80% forested) sub-basins of the upper Little Tennessee River Basin in the southern Blue Ridge were identified for comparison. The pairs contain physically similar stream reaches, chosen for the purpose of isolating forest conversion as a potential driver of any detected differences in water quality. Streams were sampled during baseflow conditions twice monthly over a six-month period from September 2003 through February 2004. Parametric t-tests were run for each parameter measured between the lightly- and moderately-impacted streams within each pair. Statistically significantly higher mean values of suspended and dissolved solids, nitrate, specific conductivity, turbidity, and temperature were observed in the moderately-impacted streams versus the lightly-impacted streams in both pairs, while dissolved oxygen levels were lower in the moderately-impacted streams. No significant differences were demonstrated in orthophosphate or ammonium concentration. A near-bankfull runoff event on February 6, 2004, was sampled for stormflow values, and the results support baseflow findings. The water quality of these streams is very good when compared with lower relief areas like the Piedmont, and none of the parameters measured in this study exceeds levels of known threat to stream biota. However, the demonstration that moderate reductions in forest cover are associated with stream water quality degradation carries important implications for stream management in this rapidly developing mountainous region.

Price, K., and D.S. Leigh. 2006. Morphological and sedimentological responses of streams to human impact in the southern Blue Ridge Mountains, USA. Geomorphology. 78: 142-160.

Abstract
Morphological and sedimentological responses of streams to basin-scale impact have been well documented for intensively agricultural or urban areas. Sensitivity thresholds of streams to modest levels of disturbance, however, are not well understood. This study addresses the influence of forest conversion on streams of the southern Blue Ridge Mountains, a region that has received little attention with respect to human impact on stream channels. Basins were chosen for this study to represent the end members of the range of human impact in the area, with the forest cover of the basin used as a proxy for level of impact (ranging from about 70v100% regionally). Two pairs of lightly impacted (N90% forest) and moderately impacted (70v80% forest) sub-basins of the upper Little Tennessee drainage area, and riparian cover) were aligned in each pair to isolate contrasting forest cover as the primary driver of any detected differences in morphology and sedimentology. A suite of standard cross-sectional and longitudinal data was collected for each reach for characterization of the sedimentology and morphology of the streams. Difference of means tests were conducted to identify parameters significantly differing between the lightly and moderately impacted streams in both pairs. Consistent and significant differences within both pairs were demonstrated in bankfull width/depth ratios, baseflow wetted width, and particle size on the stream bed both in the thalweg and throughout the channel bed. The moderately impacted streams are narrower than the lightly impacted streams, and the bed texture of the moderately impacted streams is finer than that of the lightly impacted streams. The moderately impacted streams contain a higher percentage of <2mm particles in riffles, a metric which has been shown to be highly correlated with biotic integrity in the southern Appalachian Highlands. Although this study has shown that human impact in these basins has resulted in an overall fining of bed texture, few conclusions can be drawn regarding the morphological response of the streams to the levels of impact affecting the upper Little Tennessee River basin. Levels of disturbance in the southern Blue Ridge Mountains may be below the thresholds of morphological sensitivity or have not persisted for sufficient duration for morphological response to be evident. Additionally, morphological adjustment to disturbance may be more effectively addressed system-wide, as opposed to at the reach scale.

Scott, M.C. 2006. Winners and losers among stream fishes in relation to land use legacies and urban development in the southeastern US. Biological Conservation. 127: 301-309.

Abstract
The southeastern United States is a center of aquatic species diversity and endemism in North America, but many taxa are imperiled or in decline. Proactive conservation strategies depend on developing sensitive measures of ecological response to environmental degradation early in the process. In the southern Appalachian highlands, much of the region has reforested following extensive logging and agriculture in the last century, but recently exurban development has surged. Patterns of aquatic ecosystem response to these changes were examined in 36 watersheds along a gradient of forest cover from moderately to heavily forested. A linear combination of watershed-scale measure reflecting the extent contemporary forest cover, the trajectory of forest cover change over time, and building and road density were stronger predictors of fish assemblage composition than topographic features. A measure of biotic homogenization relating the abundance of endemic highland fishes to abundance of broad-ranged fishes was sensitive to the gradient of anthropogenic disturbance. Across the watershed disturbance, gradient, cosmopolitan species were clear winners as forms unique to the Appalachian highlands were lost. Similar measures of homogenization may be suitable elsewhere for tracking early warning signs of ecosystem stress, particularly in regions with significant endemism. Quantification of the homogenization process in response to urban development and other stressors is a promising avenue for proactive conservation, land use planning, and sustainable, development efforts.

Sun, G., G. Zhou, Z. Zhang, X. Wei, S.G. McNulty, and J.M. Vose. 2006. Potential water yield reduction due to forestation across China. Journal of Hydrology. 328: 548-558.

Abstract
It is widely recognized that vegetation restoration will have positive effects on watershed health by reducing soil erosion and non-point source pollution, enhancing terrestrial and aquatic habitat, and increasing ecosystem carbon sequestration. However, the hydrologic consequences of forestation on degraded lands are not well studied in the forest hydrology community as a whole. China has the largest area of forest plantations in the world now, and the hydrologic consequences of massive forestation are unknown. We applied a simplified hydrological model across the diverse physiographic region to estimate the potential magnitude of annual water yield response to forestation. Our study suggests that the average water yield reduction may vary from about 50 mm/yr (50%) in the semi-arid Loess Plateau region in northern China to about 300 mm/yr (30%) in the tropical southern region. We conclude that forestation in China that often involves a combination of tree planting and engineering (e.g., terracing) may have even a higher potential to greatly reduce annual water yield in headwater watersheds, especially in the semi-arid Loess Plateau region. However, the forestation area is relatively small for most large basins with mixed landuses in China, thus the regional effects of forestation on water resource management may not be of major concern. Comprehensives science-based evaluation of roles of forests on regulating regional water resources is critical to the current forestation endeavors in China.

Tirpak, J.M., W.M. Giuliano, C.A. Miller, T.J. Allen, S. Bittner, D.A. Buehler, J.W. Edwards, C.A. Harper, W.K. Igo, G.W. Norman, M. Seamster, and D.F. Stauffer. 2006. Ruffed grouse population dynamics in the central and southern Appalachians. Biological Conservation 133(3): 364-378.

Abstract
Ruffed grouse (Bonasa umbellus; hereafter grouse) populations in the central and southern Appalachians are in decline. However, limited information on the dynamics of these populations prevents the development of effective management strategies to reverse these trends. We used radiotelementry data collected on grouse to parameterize 6 models of population growth to: (1) determinetion models were most similar to trend estimates derived from Breeding Bird Survey and Christmas Bird Count data when models incorporated either a reproductive or survival event. These events randomly increased fecundity or survival, respectively, to their empirical maxima on average once every 5 years. Reproductive events improved estimates on areas dominated by mixed mesophytic forest, while survival events characterized population growth on oak (Quercus spp.)-dominated sites. The finite rate of increase (d) was most sensitive to brood survival followed by adult and juvenile non-breeding survival on most sites. However, brood survival was low (<0.35 female chicks/hen survived to week 5), and elasticity analyses indicated d responded more strongly to proportionate change in non-breeding and breeding survival rates of adults and juveniles than any reproductive variable. Life stage analyses corroborated this result. At baseline values, survival of adults and juveniles may be the main determinants of growth in these populations, and reproduction may not be adequate to compensate for these losses. Therefore, population growth above baseline levels may be regularly needed to restock these populations. Researchers have hypothesized that population dynamics may differ between mixed mesopytic and oak-dominated sites due to differences in forage quality and quantity. Thus, a potential mechanism for the increases in d needed to sustain populations on mixed mesophytic forest sites is the greater fecundity observed during years with high oak or beech (Fagus grandifolia) mast abundance. The availability of this high quality forage allows hens to enter the breeding season in better condition and realize higher fertility. Alternatively, on oak-dominated sites, population growth increases may also be a product of higher non-breeding survival of birds in mast years, when birds do not need to range as far to forage and can limit their exposure to predators.

Adams, R.K., and J.A. Spotila. 2005. The form and function of headwater streams based on field and modeling investigations in the Southern Appalachian Mountains. Earth Surface Processes and Landforms. 30: 1521-1546.

Abstract
Headwater streams drain the majority of most landscapes, yet less is known about their morphology and sediment transport processes than for lowland rivers. We have studied headwater channel form, discharge and erosive power in the humid, moderate-relief Valley and Ridge and Blue Ridge provinces of the Appalachian Mountains. Field observations from nine headwater (<2 km2 drainage area), mixed bedrockvalluvial channels in a variety of boundary conditions demonstrate variation with respect to slope-area channel initiation, basic morphology, slope distribution, hydraulic geometry, substrate grain size and role of woody debris. These channels display only some of the typical downstream trends expected of larger, lowland rivers. Variations are controlled mainly by differences in bedrock resistance, from the formation level down to short-wavelength, outcrop-scale variations. Hydrologic modeling on these ungauged channels estimates the recurrence of channel-filling discharge and its ability to erode the channel bed. Two-year recurrence discharge is generally larger and closer to bankfull height in the Valley and Ridge, due to low soil infiltration capacity. Discharge that fills the channel to its surveyed bankfull form is variable, generally exceeding two-year flows at small drainage areas (<0+5 km2) and being exceeded by them at greater drainage areas. This suggests bankfull is not controlled by the same recurrence storm throughout a channel or physiographic region. Stream power and relative competence are also variable. These heterogeneities contrast relations observed in larger streams and illustrate the sensitivity of headwater channels to local knickpoints of resistant bedrock and armoring of channels by influx of coarse debris from hillslopes. The general lack of predictable trends or functional relationships among hydraulic variables and the close coupling of channel form and function with local boundary conditions indicate that headwater streams pose a significant challenge to landscape evolution modeling.

Beckage, B., and J. Clark. 2005. Does predation contribute to tree diversity? Oecologia. 143: 458-469.

Abstract
Seed and seedling predation may differentially affect competitively superior tree species to increase the relative recruitment success of poor competitors and contribute to the coexistence of tree species. We examined the effect of seed and seedling predation on the seedling recruitment of three tree species, Acer rubrum (red maple), Liriodendron tulipifera (yellow poplar), and Quercus rubra (northern red oak), over three years by manipulating seed and seedling exposure to predators under contrasting microsite conditions of shrub cover, leaf litter, and overstory canopy. Species rankings of seedling emergence were constant across microsites, regardless of exposure to seed predators, but varied across years. A. rubrum had the highest emergence probabilities across microsites in 1997, but Q. rubra had the highest emergence probabilities in 1999. Predators decreased seedling survival uniformly across species, but did not affect relative growth rates (RGRs). Q. rubra had the highest seedling survivorship across microsites, while L. tulipifera had the highest RGRs. Our results suggest that annual variability in recruitment success contributes more to seedling diversity than differential predation across microsites. We synthesized our results from separate seedling emergence and survival experiments to project seedling bank composition. With equal fecundity assumed across species, Q. rubra dominated the seedling bank, capturing 90% of the regeneration sites on average, followed by A. rubrum (8% of sites) and L. tulipifera (2% of sites). When seed abundance was weighted by species-specific fecundity, seedling bank composition was more diverse; L. tulipifera captured 62% of the regeneration sites, followed by A. rubrum (21% of sites) and Q. rubra (17% of sites). Tradeoffs between seedling performance and fecundity may promote the diversity of seedling regeneration by increasing the probability of inferior competitors capturing regeneration sites.

Beckage, B., M. Lavine, and J. Clark. 2005. Survival of tree seedlings across space and time: estimates from long-term count data. Journal of Ecology. 93: 1177-1184.

Abstract
(1) Tree diversity in forests may be maintained by variability in seedling recruitment. Although forest ecologists have emphasized the importance of canopy gaps in generating spatial variability that might promote tree regeneration, the effects of canopy gaps on seedling recruitment may be offset by dense forest understories. (2) Large annual fluctuations in recruitment processes, coupled with the long life of forest trees, can provide an alternative mechanism for maintaining tree diversity. Evaluating the relative importance of spatial vs. temporal variability in recruitment, however, requires estimates of seedling survival that are extensive on both scales. (3) Estimates of survival derived from conventional statistical methods require that individual seedlings are monitored through time, and are therefore often limited in extent. (4) We demonstrate a relatively fast and easy alternative approach to measuring survival that uses repeated counts of individuals in quadrats. (5) Annual seedling counts were used to quantify both the effects of small canopy gaps and understorey shrubs on the survival of Acer rubrum (red maple) seedlings and the magnitude of residual spatial and temporal variability in seedling survival. (6) We found that a dense understorey had a greater effect on seedling survival than did canopy gaps. Our canopy gaps had only a slight positive effect on seedling survival, and their benefit was offset by a large negative effect of the understorey shrub Rhododendron maximum. (7) Annual fluctuations in recruitment processes were seven times greater than spatial variability across transects and the effect of individual years on seedling survival was larger than even that of understorey shrubs. (8) The long life span of trees coupled with large annual variability in recruitment success across species may maintain the diversity of forest trees through a storage effect.

Beier, C.M., J.L. Horton, J.F. Walker,B.D. Clinton, and E.T. Nilsen. 2005. Carbon limitation leads to suppression of first year oak seedlings beneath evergreen understory shrubs in Southern Appalachian hardwood forests. Plant Ecology. 176: 131-142.

Abstract
Inhibition of canopy tree recruitment beneath thickets of the evergreen shrubs Rhododendron maximum L. and Kalmia latifolia L. has long been observed in Southern Appalachian forests, yet the mechanisms of this process remain unresolved. We present a first-year account of suppression of oak seedlings in relation to Rhododendron and Kalmia basal area, light and resource availability, seedling performance and the rates of seedling damage (i.e., herbivory). We found no evidence of first-year seedling suppression or significant resource deficiencies beneath thickets of K. latifolia in mature mixed hardwood stands. Suppression beneath R. maximum was apparent during the first growing season. We found that seedling biomass, light availability prior to canopy closure, and seedling tissue C:N ratios were negatively correlated with R. maximum basal area. Basal area of R. maximum was positively correlated with seedling mortality rates, soil [Al], and early-growing season leaf herbivory rates. Seedling growth was positively correlated with light and tissue C:N, while negatively correlated with soil [Al]. Overall, our results support the inhibition model of shade-mediated carbon limitation beneath dense understory shrubs and indicate the potential importance of herbivory and aluminum toxicity as components of a suppression mechanism beneath R. maximum thickets. We present a causal model of first year inhibition beneath R. maximum in the context of our findings and the results of prior studies. Rosenfeld, Brian Jay. 2003. Developing a new fuel load mapping strategy using: digital photogrammetry; international classification of ecological communities; USDA Forest Service, forest inventory and analysis protocols; and disturbance history. Price, Myra Ann. 1998. Seasonal variation in runoff curve number. Tuscon, AZ: Univeristy of Arizona. 189 p. M.S. thesis. Hawkins, Richard H. 1993. Asymptotic determination of runoff curve numbers from data. Journal of Irrigation and Drainage Engineering. 119(2): 334-345. Background, general instructions, and examples are given fodirect runoff data sets. The technique matches rank-ordered (i.e., sorted) rainfall and runoffs, which preserves the return-period matching between the rainfalls and the runoffs. Usually a secondary trend

Bolstad, P.V., and J.M. Vose. 2005. Forest and Pasture Carbon Pools and Soil Respiration in the Southern Appalachian Mountains. Forest Science. 51(4): 372-383.

Abstract
Our ability to estimate the changes in carbon (C) pools and fluxes due to forest conversion is hampered by a lack of comparative studies. We measured above- and belowground C pools and soil respiration flux at four forested and four pasture sites in the southern Appalachian Mountains. Above- and belowground C pools were significantly larger (P < 0.01, t-test) at forested sites relative to pasture sites. The largest differences were in aboveground live biomass, which averaged 152 Mg ha-' C at the forested sites and 1.9 Mg ha-' at the pasture sites. Coarse root and stump C and surface detritus were also substantially different, averaging 41.3 and 32.6 Mg ha-' C, respectively, at the forested sites, and less than 1 Mg ha-' at the pasture sites. Fine root C was higher and mineral soil C lower at pasture sites relative to comparable forested sites, but neither difference was statistically significant. Soil respiration at a given temperature was generally lower at pasture sites relative to forest sites. However, soil temperatures at pastures were consistently higher than at forest sites. Estimated annual soil respiration flux averaged 10.9 Mg C ha- ' at the pasture sites and 12.6 Mg C ha-' at the forested sites.

Brookshire, E.N.J., H.M. Valett, S.A. Thomas, and J.R. Webster. 2005. Coupled cycling of dissolved organic nitrogen and carbon in forest streams. Ecology 86(9): 2487-2496.

Abstract
Dissolved organic nitrogen (DON) is an abundant but poorly understood pool of N in many ecosystems. We assessed DON cycling in a N-limited headwater forest stream via whole-ecosystem additions of dissolved inorganic nitrogen (DIN) and labile dissolved organic matter (DOM), hydrologic transport and biogeochemical modeling, and laboratory experiments with native sediments. We sampled surface and subsurface waters to understand how interaction among hydrologic exchange, DIN, DON, and dissolved organic carbon (DOC) influence stream N losses at summer baseflow. Added DON was taken up rapidly from the water column at rates exceeding DOC and DIN. A significant fraction of this DON was mineralized and nitrified. Combined DON and NO3-N uptake lengths resulted in spiraling lengths of ;210 m, suggesting the potential for multiple transformations of labile N loads within catchment boundaries. Simultaneous addition of DIN increased DOM uptake, but more so for C, resulting in an upward shift in the C:N ratio of uptake. Sediment incubations also showed a strong biotic influence on DOC and DON dynamics. Despite efficient uptake of added DOM, background DON and high molecular mass DOC concentrations increased downstream, resulting in higher DOM loads than could be accounted for by groundwater discharge and suggesting net release of less bioavailable forms from the channel/hyporheic zone. At the same time, subsurface DOM was characterized by very low C:N ratios and a disproportionately large DON pool despite rapid hydrologic mixing with dilute and high C:N ratio surface waters. Analysis