Nonlinear effects of consumer density on multiple ecosystem processes

摘要: Summary 1. In the face of human-induced declines in abundance common species, ecologists have become interested quantifying how changes density affect rates biophysical processes, hence ecosystem function. We manipulated a dominant detritivore (the cased caddisfly, Limnephilus externus) subalpine ponds to measure effects on release detritus-bound nutrients and energy. 2. Detritus decay (k, mass loss) increased threefold, loss nitrogen (N) phosphorus (P) from detrital substrates doubled across range historically observed caddisfly densities. Ammonium total soluble concentrations water column also with some dates. Decay rates, nutrient change biomass all exhibited threshold or declining responses at highest densities. 3. We attributed these processes intraspecific competition for limiting resources manifested population level, as density-dependent per-capita consumption, growth, development case : body size caddisflies was observed. Moreover, increasingly grazed algae high densities, presumably response resources. 4. These results provide evidence that species will nonlinear, level. Given ubiquity negative dependence nature, nonlinear consumer density–ecosystem function relationships should be ecosystems.