Soil organism influence on ecosystem-level processes bypassing the ecological hierarchy?

We discuss the paradox of the apparent simplicity of ecosystem process control and the high diversity of (soil) organisms. Simple process models usually can predict, e.g., decomposition and nitrogen mineralization, without explicitly including organism biomass, species diversity or abundance dynamics. Based on these and other observations, we discuss a way of describing ecosystems that is consistent with observations at only two organizational levels (the ecosystem and the organism level). The usefulness of intermediate organizational level is questioned and the ecosystem is compared with a gas container, acting as an 'averaging engine'. We also discuss under which conditions this simple approach may not be sufficient for a valid description of an ecosystem process. (C) 1999 Elsevier Science B.V.