How would one go about estimating litter production (fine root turnover, leaves, etc.) for a forested area? I have some estimates from literature - which were derived from models, but I'd like to create my own estimate to compare.
The 1967 International Biological Programme has a handbook of suggestions for various methods to calculate primary productivity of forests. A subset of these measures would be effective for measuring litter production.
Regarding leaves and other falling litter,
Bags suspended from hoops (Ovington & Murray 1964) about 1 m above the soil. The hoops would be at least 0.5 m in diameter. The bag should be freely permeable to water (nylon mesh, cheese cloth, sail cloth, etc.) to reduce moisture and decomposition inside the bag. Care must be taken with this type of litter trap that the hoop does not incline out of the horizontal and the bag must be pegged or weighted to prevent it blowing inside out.
Further, the handbook suggests no less than 20 leaf traps in one sample area, and checking contents every week especially in moist areas. Also, to account for branch fall, the weekly collection should check for and weigh fallen branches in a 20m X 20m area.
For fine roots:
An additional estimate of fine roots can be obtained either by excavation of soil monoliths, or by taking soil cores (e.g. Bray, Lawrence & Pearson 1959) down to a depth of at least 50 cm and washing out the fine roots over a sieve. So far as is possible only live roots should be included.
For ground cover:
Where distinct plants of a single or only a few species are present, the best procedure will be to collect a number of individual plants of each species (preferably including subterranean organs) at monthly intervals through the year. The collected plants are separated into leaves, flowers, stems and roots, which are dried and weighed. These individual plant data can then be combined with density (number of individual plants/area) data for conversion to an area basis. The sum of (Species A max. biomass - min. biomass) + (Species B max. biomass min. biomass) ... gives an estimate of net production.
I believe that should account for the significant components of litter production.