Agricultural intensification, soil biodiversity and agroecosystem function

Soil is the habitat of plant roots and of a diverse array of organisms-bacteria, fungi, protozoa and invertebrate animals -which contribute to the maintenance and productivity of agroecosystems. As intensification occurs, the regulation of functions through soil biodiversity is progressively replaced by regulation through chemical and mechanical inputs, However, the causal relationships between (1) composition, diversity and abundance of soil organisms and (2) sustained soil fertility are unclear. Furthermore, in tropical agricultural systems undergoing intensification, large numbers of farmers have limited access to inputs, and therefore the maintenance and enhancement of soil biodiversity may be particularly relevant to such farmers. In this paper we propose a number of hypotheses which could be tested to explore the relationships between agricultural intensification, biodiversity in tropical soils and ecosystem functions. We also provide a conceptual framework within which such hypotheses can be tested. (C) 1997 Elsevier Science B.V.