Soil Fungi and Macrofauna in the Neotropics

Abstract

Decomposition is a critical ecosystem function that decomposes dead organic materials, removes wastes, recycles nutrients and renews soil fertility. In natural ecosystems most nitrogen (N) and phosphorous (P) required for plant growth are supplied through the decomposition of detritus, relying therefore on the activities of soil microbes and macrofauna. Decomposition is a consequence of interacting physical and chemical processes occurring inside and outside of living organisms in an ecosystem (Chapin III et al. 2002). The two major processes include fragmentation, breaking larger pieces of organic mater into smaller ones, and chemical alteration, the change of chemical elements of dead organic mater into others. Fragmentation is largely a consequence of feeding activity of soil macrofauna and chemical alteration is primarily associated with the activity of bacteria and fungi. Land conversion from forests to pasture or agricultural land alters the belowground ecosystem and decomposition process, and depletion of soil organic C (Doran and Zeiss 2000). Degradation processes such as losses in soil C, nutrient depletion and reduced water holding capacity often lead to considerable change in soil microbial community and macrofuana (Bever et al. 1996, Picone 2000, Thomas et al. 2004). In the Neotropics, land conversion from tropical forest to agricultural land and then to pasture is the most common kind of land use practices (Fearnside 1993, Thomlinson 1996, Cleveland et al. 2003). Studies of the dynamics of microbes and macrofauna following land conversion are thus particularly of importance for establishing effective strategies of post-agriculture recovery and forest ecosystem restoration because soil microbial community and soil macrofauna play a key role in successional pathways.