Litterbag Construction

Various types of netting have been used for litterbags. Mosquito netting, nylon drapery mesh, and plastic window screen are suitable materials. Cloth bags must be sewed together. Plastic screen bags may be constructed by using a soldering iron to melt and seal the edges of the bag. Cloth bags are more flexible, conform to the shape of the forest floor, and admit more fauna because the mesh openings are more flexible. Window screen bags are more rigid and openings are fixed, but they are much easier to construct. Size of bags has ranged from 0.25 square meter (m2) down to 10 millimeters (mm); 10 cm by 10 cm (one decimeter) is a frequently used dimension. Actual dimensions of 12-by-12cm yield an effective area of about 100 cm2. A flap on the open end of the bag allows it to be closed with a safety pin.

Leaf litter substrates should be air dried if possible before insertion into the litterbags. We use contrasting litters with different palatabili-ties, carbon-nitrogen ratios, etc., such as dogwood, chestnut oak, or rhododendron. Decimeter litterbags will contain about 1.5 g of dry deciduous leaf material before breakage becomes a problem. After mass determination, an identifying label may be placed inside the litterbag. (Aluminum tags attached outside the bags tend to attract large mammals.)

Place the bags out in field sites such as old fields, forest floor, or agricultural fields. On each sample date, randomly select four replicate litter bags from each of several treatments. Upon retrieval, litterbags should be placed in plastic bags and returned to the laboratory as soon as possible. The bag may be opened and a small increment removed for nematode extraction (with suitable estimation of litter mass). The intact litterbag may then be extracted on a Tullgren funnel. Finally, the litter substrate is removed from the bag for mass determination. Process the litter using the following steps:

1. Clean the outside of the litterbag (brush off any sand and litter particles).

2. Remove the metal label; record its number, the pick-up date, treatment code, and your initials on a new label.

3. Weigh a beaker (with tape label on it) and record on weighing sheet.

4. Above a piece of waxed paper, carefully take all the litter material out of the litterbag and put it into the beaker. If there was any soil intrusion into the litterbag, make sure you remove the soil before you put the litter in the beaker. Put the beaker in the 60°C oven and dry the litter for a minimum of 2 days.

5. After at least 2 days, record the dry weight (beaker + litter dry weight) and transfer the litter to a labeled paper bag.

0 0

Post a comment