Germination Biology and the Ecology of Annual Plants

We derive spatially explicit population models for the interaction between a species of annual plant and a community of perennial species. The models are used to explore the conditions for persistence of the annual in both a constant and a stochastic environment. In both types of environment a seed's response to the presence of established perennial plants is found to affect strongly the conditions for persistence. Sensitivity analysis of a parameterized version of the model indicates the importance of germination and mortality parameters in allowing persistence. In the parameterized model large changes in fecundity have little effect on the condition for persistence. The implications of these results for the distribution of annual plants and the forces structuring communities of short-lived plants in successional habitats are discussed.