Body size, energy consumption and allometric scaling: a new dimension in the diversity?stability debate

Abstract

A new theoretical approach is developed that links the allometry of energy partitioning among differently-sized organisms in ecological community to community stability. The magnitude of fluctuations of plant biomass introduced by plant-feeding heterotrophs is shown to grow rapidly with increasing body size. To keep these fluctuations at a low level compatible with ecosystem stability, the share of ecosystem primary productivity claimed by plant-feeding heterotrophs should decrease with increasing body size. In unstable environments the ecological restrictions on biotic fluctuations are lessened and net primary productivity can be distributed more evenly among differently sized organisms. Within the developed approach it is possible to quantitatively estimate not only the scaling exponents in the dependence of population density and biomass of heterotrophs on body size, but also the absolute values of energy fluxes claimed by organisms of a given size in stable communities. Theoretical predictions are tested against diverse sets of empirical data. It is shown that in stable ecological communities the largest heterotrophs are allowed to consume no more than several tenths of percent of net primary productivity.