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Leaf litter collections and sorting

Article ID: 5
Last updated: 12 Mar, 2014

Materials:
Brush and dust pan
Paper bags
Sharpies
Laundry sacks
Staple gun (for trap repairs)

Description:
Canopy leaves and other litterfall inputs to the forest floor are sampled by litterfall traps, which are installed on study plots and the sample collected at regular intervals. Our litter traps are 0.85 m2 and are constructed of 2.54 x 15.24 cm (2 x 6 inch) wood composite, with stainless steel screen covering the bottom side and beveled edges or sheet aluminum defining the sample area on top. Traps are usually secured with 2.54 x 5.08 cm (1 x 2 inch) aluminum stakes holding the sample area level to earth. Samples are collected quarterly except in the fall quarter when they are collected monthly.  

Methods:
There are 10 litterfall traps at each of the five terrestrial gradient research plots (50 traps total) and 5 litterfall baskets at each of the 12 functional diversity plots (60 traps total). Collections should be scheduled for both studies at the end of June, September, October, November, December, and March. This collection schedule covers the four quarterly collections with monthly collections during the autumn when high leaf litter inputs are occurring. For ease of collection, samples should be collected after it has been dry for a couple days if possible.  All bags should be labeled with the site, trap number, date, collection year (e.g. CY 18), and quarter numberBags should be immediately dried at 65 degrees C before placing bags in attic.

 Bags of leaves should be well-organized in the attic, making sure that all collections are accounted for and are placed in the same large bag or box that is clearly labeled.

 If there are a backlog of leaves, the earliest collections should be sorted first, dried, weighed, and leaf weight data entered before moving on to another quarter to sort.  This will help insure consecutive quarters are not combined.

After leaves are weighed and data entered, technicians should notify the Site Manager so he/she can QA/QC the data before the technician moves on to the next quarter.  Data should be entered into the master spreadsheet located on the Coweeta server (i.e. the Z drive). Before entering the data, a copy should be made on the desktop in case the master file becomes corrupted while entering the data.  QA/QC procedures include looking for outliers and making sure columns such as plot, trap number, and dates have been entered correctly.   Having a more frequent QA/QC process will also help to eliminate quarters being combined.

Interns are to be closely supervised when sorting leaves. They should be given clear instructions and only allowed to sort leaves from one quarter that has been previously organized to make sure all samples are accounted for and that only samples from that particular quarter are included. Ideally, interns should not be left alone to sort leaves, but if they are left alone, the technician should work together with the intern to sort through a minimum of 3 leaf litter sample bags to make sure the interns understand the protocols. Technicians or the Site Manager should check in on the progress of the sorting around lunchtime and again at the end of the day. If the student is weighing samples, technicians should watch the student weigh at least 5 samples before the students are to be left on their own.

Terrestrial gradient:
The litter from each 91.4 x 91.4 cm trap is to be collected at least once each quarter (January to March, April to June, July to September, October to December) preferably near the end of each three month quarter. More frequent collection is needed during the October to December quarter (once a month) due to heavy litter fall.

The samples should be sorted for each trap into the following categories:

Deciduous Leaves including Mountain Laurel Leaves
Rhododendron Leaves
Pine Leaves
Woody Twigs <2.5 cm diameter
Woody Twigs 2.5 - 10 cm in diameter*
Other Including hemlock eaves, loose bark, nuts, etc.
*Prior to March 2009, only woody twigs <2.5 cm in diameter were collected.

To keep categories and labeling consistent for both the litterfall dry mass data and chemistry data, both bags with sorted material and vials with ground material should be labeled using the following criteria:

  1. Title of research project
  2. Plot
  3. Trap ID (only on original collection bag)
  4. Year
  5. Collection Year
  6. Quarter
  7. Category

So that a collection made January 3, 2014 on 527 would be labeled on both the sorted bag and scintillation vial of ground material:

  • Gradient Litterfall
  • 527
  • 2013 (because the collection is part of Q3 of 2013)
  • CY 20
  • Q3
  • Deciduous (or Pine, Rhododedron, Other, Twigs 2.5, Twigs 2.5-10)

The samples should then be dried to a constant mass at 65° C and weighed to the nearest 0.01 g. This can be facilitated by using the same sized-bags and taking the tare mass of at least 5 empty, dried bags. This minimizes the need to empty each bag when weighing. Tare mass can vary considerably between sets of bags that are the same size, but were produced at different times or by different manufacturers. This variance will result in direct error of the litter sample mass. If there is any question about the correct tare mass, please empty the litter sample into a tared weighing boat.

After collecting, drying, and weighing, the samples need to be composited to the following categories before grinding (see next page) for each quarter. The traps (A to J) from each of the five sites need to be combined. All collections during each three month period need to be combined. Typically, there is only one collection for each three month period except for October to December when there may be multiple collections due to the heavy litter fall. This compositing system will result in a set of ground samples for each three month period.

Quarter Months Year
1 April-June 1
2 July-Sept. 1
3 Oct.-Dec. 1
4 Jan.-March 2

For each quarter, site, and category, one homogeneous 25 mL sample vial of ground tissue are retained to insure adequate sample mass for future analyses. This will yield at maximum 5 sites x 6 categories x 1 vial for each category x 4 quarters = 120 vials of sample per year. However, pine is typically only present at the 118 site, rhododendron is not consistently in the traps at all sites, and many pooled samples only yield one vial of sample per quarter. Therefore, it is common to have less than 100 vials of ground tissue per year for all terrestrial gradient litter samples.

Functional Diversity:

For deciduous leaves, all sample collections for the entire litter fall year (01 April through 30 March) are combined into one sample (e.g. deciduous litter for trap 1C1 for June 27, Sept 30, Oct 18, Dec 12, and Mar 27 are combined and ground together after obtaining individual dry mass values at 65° C)

Total annual composited samples = 60 deciduous, 12 Rhodo, 12 hemlock, 12 other = 96

Plot Number Treatment (C or T) Trap Number Deciduous Leaves Rhododendron Leaves Hemlock Leaves Other and Twigs
1 C 1 sample combine below combine below combine below
1 C 2 sample combine below combine below combine below
1 C 3 sample sample sample sample
1 C 4 sample combine above combine above combine above
1 C 5 sample combine above combine above combine above
1 T 1 sample combine below combine below combine below
1 T 2 sample combine below combine below combine below
1 T 3 sample sample sample sample
1 T 4 sample combine above combine above combine above
1 T 5 sample combine above combine above combine above
2 C 1 sample combine below combine below combine below
2 C 2 sample combine below combine below combine below
2 C 3 sample sample sample sample
2 C 4 sample combine above combine above combine above
2 C 5 sample combine above combine above combine above
2 T 1 sample combine below combine below combine below
2 T 2 sample combine below combine below combine below
2 T 3 sample sample sample sample
2 T 4 sample combine above combine above combine above
2 T 5 sample combine above combine above combine above
3 C 1 sample combine below combine below combine below
3 C 2 sample combine below combine below combine below
3 C 3 sample sample sample sample
3 C 4 sample combine above combine above combine above
3 C 5 sample combine above combine above combine above
4 C 1 sample combine below combine below combine below
4 C 2 sample combine below combine below combine below
4 C 3 sample sample sample sample
4 C 4 sample combine above combine above combine above
4 C 5 sample combine above combine above combine above
4 T 1 sample combine below combine below combine below
4 T 2 sample combine below combine below combine below
4 T 3 sample sample sample sample
4 T 4 sample combine above combine above combine above
4 T 5 sample combine above combine above combine above
5 C 1 sample combine below combine below combine below
5 C 2 sample combine below combine below combine below
5 C 3 sample sample sample sample
5 C 4 sample combine above combine above combine above
5 C 5 sample combine above combine above combine above
5 T 1 sample combine below combine below combine below
5 T 2 sample combine below combine below combine below
5 T 3 sample sample sample sample
5 T 4 sample combine above combine above combine above
5 T 5 sample combine above combine above combine above
6 C 1 sample combine below combine below combine below
6 C 2 sample combine below combine below combine below
6 C 3 sample sample sample sample
6 C 4 sample combine above combine above combine above
6 C 5 sample combine above combine above combine above
6 T 1 sample combine below combine below combine below
6 T 2 sample combine below combine below combine below
6 T 3 sample sample sample sample
6 T 4 sample combine above combine above combine above
6 T 5 sample combine above combine above combine above

Weighing:
Litter should be thoroughly dried before weighing. This includes re-drying the litter overnight if the litter has already been dried, sorted, and stored. Litter to be weighed should come directly from the drying oven. Even litter left a few hours out of the oven will begin to absorb moisture from the air and gain mass.

Litter can be weighed in the bag. However, 1) make sure to tare the bag weight, or 2) weigh at least 4-5 dried, empty bags of the same type and subtract the average weight of these bags from the weight of the bags of litter. Important - make sure bags are from the same manufacturer. Even bags that are the same size may weigh ±1g if they are from different manufacturers or even from different “runs” – double check to make sure the tared bags and bags with leaf litter are the same.

You may also empty the contents of the bag into a small lightweight container. Ideally, the container should not weigh much more than the litter. Make sure the container is tared before weighing. If you have just a small amount of litter, weigh the material directly on the scale. The readings become distorted if you try to weigh 2-3 hemlock needles in a bag or container that weighs 1000× the weight of the needles. If litter is too small to register on the scale, make a note of it on the comments. Do not record 0.01 if the weight of the needle or leaf fragment is beyond the detection limit of the instrument (i.e., the instrument reads 0.00 even with leaf fragments/needles on the scale). If you have questions or are unsure about how to use the scale, please ask for help.

Use an existing Excel spreadsheet to record the data directly in the computer. Double-check to make sure the data you are entering are correct and that you are entering the data in the correct column.

Weighing can be tedious, but it is important work. Much of the chemistry data from the ground leaf litter is related back to the mass of the litter collected, so it is important to have quality control measures for the litter weights.

Grinding:
Primary goals are to perform safe operations of the coarse grinder, safe operations of the fine grinder, and produce quality samples. Quality samples have the following characteristics: (1) well mixed and representative of the entire original material, (2) minimize cross contamination among samples, (3) appropriately filled and labeled vials for analysis and archiving.

Safety

  1. Ear Plugs –at all times in grinding room
  2. Dust Mask –when grinding and cleaning
  3. Safety glasses –when grinding
  4. Dust collection switch –ON while grinding
  5. Grinder Jam/Malfunction –Immediately turn off grinder. Be aware of electrical plug locations and unplug if necessary. Once power is off, open the grinder door. Then proceed to remove jammed material.

General Information

  1. Grind like tissues (all deciduous, rhodo, twig)
  2. With very small samples (hemlock, pine), do not coarse grind. Feed directly into fine grinder (will need to prepare pine needles by cutting into small pieces).
  3. Thoroughly clean the grinders and your work area when finished.

Coarse Grinding

  1. Make sure the unit is clean before beginning
  2. Close door and turn grinder ON.
  3. Feed samples into the hopper, using large wood plunger if necessary.
  4. Use throat plate as necessary to prevent debris from flying out of top.
  5. Empty collection cup as necessary (turn grinder off first)
  6. Remove collection cup when grinding is finished, place large bowl under front of grinder, open grinder and sweep material out of grinder into bowl using paint brush
  7. Combine all materials and thoroughly mix.
  8. Clean the grinder, paint brush, & mixing bowl by brushing/vacuuming.
  9. Ready for next sample.

Fine Grinding

  1. Make sure the unit is clean. Check the air filter on back of unit and vacuum as needed.
  2. Press START (12,000 rpm)
  3. Add 5 large spoonfuls of well mixed coarse material into chute without causing the motor to bog down. Grinding is very rapid. Do not use black plastic funnel inserts.
  4. Press STOP, allow a few seconds for the automatic cover to release. Open the grinder.
  5. Remove the collection bowl and use a clean paint brush with small funnel to fill vials.
  6. Fill 1 vial to 80% full*.
  7. *Archiving –If the amount pf material is less than ½ vial, do not prepare a second vial. If the amount is equal or greater than ½ vial, prepare 2 vials of equal parts.
  8. Vacuum blades, grinding wheel, cover plate, etc. If debris sticks to the lid or other parts, wipe the area with a dry paper towel and finish vacuuming.
  9. Reassemble –Be sure to align notches on collection bowl and screen with the base plate.

Article ID: 5
Last updated: 12 Mar, 2014
Revision: 1
Views: 0
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