CONSTANT-YIELD AND VARIABLE-YIELD MODELS OF POPULATION-GROWTH - RESPONSES TO ENVIRONMENTAL VARIABILITY AND IMPLICATIONS FOR COMPETITION

Constant- and variable-yield models of resource consumption and population growth are defined, and examined for their predictions concerning resource competition under non-equilibrium conditions. Constant-yield models can arise from examining the equilibria of variable-yield models. Constant-yield models thus derived are simpler than the underlying variable-yield models, and are adequate for predictions of competitive outcome at equilibrium, but err when applied to variable habitats. The use of linearization and Fourier transformation to calculate a transfer function between driving variability in the environment, and the resulting trajectory of resource availability, is advocated. The modulus of this transfer function is an indicator of competitive ability in variable habitats, can be used to identify situations in which constant-yield models are inadequate approximations of variable-yield models, and to guide simulations or non-linear analyses. © 1992 Academic Press Limited.