Soil fauna, guilds, functional groups and ecosystem processes

Soil ecology has much to contribute to our understanding of important processes at the ecosystem level such as primary production as affected by the rhizosphere biota, organic matter dynamics and nutrient cycling and soil structure dynamics. Soil animals play an important part in these processes, but it has always been difficult to single out their contributions. In studies of these processes soil ecologists often rely on 'guilds' and 'functional groups' as their basic unit of observation. Here, I evaluate the usefulness and limitations of this approach for understanding some of the above-mentioned processes. A simple conceptual model of ecological interactions in soil is presented. The plant has a central place in this model in that it both governs, and is a biological assessment of, the roles soil fauna play in ecosystem processes. The need for a quantitative model of ecological interactions in soil is discussed with reference to current modelling efforts of organic matter and food webs in soil. (C) 1998 Elsevier Science B.V.