|Title||Warmer temperatures reduce net carbon uptake, but do not affect water use, in a mature southern Appalachian forest|
|Archive||All Files / Documents / Publications / Journal Articles|
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.
|Contributors||A. Christopher Oishi, Chelcy F. Miniat, Kimberly A. Novick, Steven T. Brantley, James M, Vose and John T. Walker|
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.
|Key Words||Complex terrain, Drought, Ecosystem respiration, Gross primary productivity, Net ecosystem exchange, Net ecosystem productivity|
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