Plant Competition Experiments: Testing Hypotheses and Estimating the Probability of Coexistence

The analysis of plant competition experiments with variable plant density is discussed based on three published data sets. It is shown how conclusions regarding plant community dynamics from typical plant competition experiments can be extended and based on a statistical framework. The data are tested in hyperbolic competition models of decreasing complexity by a standard hierarchical statistical procedure. Hypotheses on the shape of the response surface curves, the number of necessary parameters, and the effects of competition on plant growth were tested using maximum likelihood ratio tests. The conditions for coexistence in a hyperbolic competition model were examined analytically. Using the found conditions for coexistence and Bayesian statistics, the probability of the four possible outcomes of two-species competition was estimated in a competition experiment with Avena fatua and A. barbata.