1.1 - Dynamic food webs

Abstract

Food webs are special descriptions of biological communities focusing on trophic interactions between consumers and resources. They have become a central issue in population, community, and ecosystem ecology. They provide a way to analyze the interrelationships among community dynamics and stability and ecosystem functioning, and how these are influenced by environmental change and disturbance. Population dynamics of interacting predators and prey are difficult to predict, and many ecosystems are known to contain hundreds or thousands of these interactions arranged in highly complex networks of direct and indirect interactions. Approaching food web structure and dynamics from environmental characteristics shows that environmental heterogeneity may create subsystems, especially at the lower trophic levels in food webs, with organisms at the higher trophic levels that act as “integrators” across this variability in space and time and stabilize dynamics of their resources via density-dependent adaptive foraging. Approaching food web structure from dynamics in populations shows that the evolution of realistic food web structures can be explained on the basis of simple rules regarding population abundance and species occurrence. The analyses of biological properties of individuals within populations show a strong explanatory power of body size to population abundance scaling rules in understanding the dynamics and persistence of trophic groups in food webs. Resource availability and use may govern the structure and functioning of food webs; in turn, food web interactions are the basis of ecosystem processes and govern important pathways in the global cycling of matter, energy, and nutrients.