Soil fauna and litter decomposition in primary and secondary forests and a polyculture system in Amazonia - study design and methodology.

A comparative study of litter quantity and qulity, decompositon rates, and the abundance, biomass, and respiration of soil-inhabiting microbes, arthropods and oligochaetes has been started in 1997. The three study sites are a primary forest, a 13-year old secondary forest and polyculture plantation system consisting of four commercially used tree species planted in rows between adventitious vegetation. The aim is to evaluate the specific contribution of the soil microflora and of the different functional soil fauna groups to the decomposition of organic matter and the resulting nutrient supply to the plants. A general description of the study design of the project is given and some methodological aspects are discussed. Methods that are standard in soil biological studies in temperate region had to be adapted to tropical conditions. For studies of litter decomposition rates using litter bags, it was suggested standard mesh sizes to be used for an ecologically relevant separation of meso- and macrofauna