Neighborhood Models of Plant Population Dynamics. 4. Single-Species and Multispecies Models of Annuals with Dormant Seeds

Abstract

Neighborhood population-dynamic models are developed for single-species and multispecies communities of annual plants with seeds that may lie dormant through one or more growing seasons. Dormancy-induced changes in lifetime germination successes affect the equilibrium densities of plants and the local stability of equilibria. Dormancy-induced population-dynamic time lags, in contrast, do not affect equilibrium densities of post-germination plants or the ability of an invader to successfully colonize a multispecies community. In single-species populations, time lags are never destabilizing but may be stabilizing. Specifically, some strategies of dormancy (a way to partition lifetime germination success among the various age classes of seeds) cause an otherwise oscillatory monoculture (eigenvalue less than negative one) to have a locally stable positive equilibrium. The maximum distance over which a plant of one species can interfere with a plant of another species is termed the neighborhood radius. The population-dynamic consequences of the sizes of the radii are examined in one- and two-species communities. The models in this paper are designed to be easily calibrated with experimental data. All results are illustrated with models calibrated for greenhouse communities of two species of annual weeds.