Soil food webs in agricultural ecosystems John C. Moore Colorado State University

Peter C. de Ruiter Wageningen University

4.1 Introduction Odum (1969) provided a framework for viewing the relationships between plant communities and biogeochemical cycles in his seminal article, “The Strategy of Ecosystem Development.” The framework is a compilation of ecosystem thinking of that time that juxtaposes ecosystem properties of early development communities with mature communities, revealing an end game of homeostasis and balance between plants and nutrients (Table 4.1). The transition from early developmental communities to mature communities is characterized structurally and functionally by a transition from r-selected to k-selected plant species, from food chains that rely primarily on primary production to ones that rely on both primary production and detritus, and from biogeochemical cycles that are open with exogenous inputs and high exports of plant-limiting nutrients to ones that are more closed and dependent on symbiotic interactions that promote internal cycling of nutrients and nutrient exchanges (Wall and Moore, 1999).