Global Overview of the Functional Roles of Soil-living Nematodes in Terrestrial Communities and Ecosystems

Abstract

The role of soil-living nematodes in different ecosystems can be largely predicted by the intensity of nonbiotic stresses imposed by different temperature and moisture regimes. Assuming that tropical lowland rain forest experiences the most biologically equitable climate, increasing climate-related stress occurs as one proceeds through intervening biomes to low latitude lowland desert, high latitude desert, and alpine desert. Soil nematodes, being mostly relative generalists, show only moderate diversity and low densities in tropical lowland rain forests because of competition from many other more specialized organisms. On the other hand, nematode diversity and densities increase and remain relatively high as one proceeds to the most extreme ecosystems because nematodes show greater adaptability than do many other taxa to climate-induced stress. However, cold allows nematodes greater "ecological release" than does drought because nematodes, being essentially aquatic organisms, require moisture for activity. Thus, cold ecosystems have the greatest nematode diversities and densities. Key words: adaptability, competition, density, diversity, ecological release, ecosystem function, global overview, nonbiotic stress.