FOOD WEBS AND ECOLOGICAL NETWORKS ACROSS TEMPORAL AND SPATIAL SCALES

A coherent description of ecosystems across a range of temporal and spatial scales is obtained by introducing non-dimensional coordinates normalized by the intrinsic scales of the populations of the organisms involved. Organisms are aggregated into dynamic classes irrespective of their taxonomic identity. The basic food web units. the trophic dynamic modules, are defined in terms of the dynamic properties of the component organisms, their location in time and space and their functional embedding within the network of energy transfers. As a result one obtains a hierarchical modular description of the spatio-temporal structure of food web interactions. Such a description can be employed as a quantitative basis for the analysis of general food web patterns. Comparisons between terrestrial and aquatic systems, and among systems exposed to different schemes of environmental variability, become feasible. Valuable information can be provided to resolve the controversy concerning the interpretation of food webs in terms of trophic levels or as a trophic continuum. The approach presented here is motivated by a view of ecosystems as dynamic nonequilibrium systems characterized by local interactions and distributed control. It is contrasted with the more common view of ecosystems as equilibrium systems characterized by centralized control.