Limiting Similarity in Mechanistic and Spatial Models of Plant Competition in Heterogeneous Environments

Abstract

We study two kinds of mechanistic and spatial models of plant competition in heterogeneous environments. First, we study lottery models in which the outcome of competition among juveniles for vacant space is determined by one of several underlying mechanistic submodels. Environmental heterogeneity that affects the outcome of competition is present in all of these models and may be spatial, temporal, biotic in origin, abiotic in origin, or any mixture of these. The principal result is that the models predict coexistence if the plant species are sufficiently dissimilar-if they sufficiently partition the spatial, temporal, biotic, or abiotic environmental heterogeneity. Second, we study a complex forest-simulation model of competition among individuals for light and a nutrient. Whereas the nonspatial version of this model predicts that a single species will outcompete all others, the spatial version predicts that coexistence is possible. We show that the results for the analytically tractable models appear to explain the cause and pattern of coexistence in the simulation model.