Spatiotemporal Demographic Processes in Plant Populations: An Approach and a Case Study

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Abstract
The present paper suggests an approach combining theory and experiments to describe and analyze the effects of seed dispersal and seed dormancy on the population dynamics of annual plants. The approach is based on the identification of three potential sources of recruitment to plant populations: (1) local reproduction; (2) the soil seed bank; and (3) the net gain from dispersal. The quantitative relationships of the three sources determine the relative importance of dispersal and dormancy in population maintenance. Mathematical expressions for the different sources in the form of specific combinations ("components") of demographic variables and parameters are derived from a dynamic model of an annual population in a spatially and temporally variable environment. An experimental procedure for quantifying the model components is described. This procedure was used to investigate the joint effects of dispersal and dormancy on the dynamics of populations of the desert annual Stipa capensis. The results confirm the use of the proposed approach and indicate that seed dormancy and, in particular, seed dispersal were important in determining spatial (between-habitats) and temporal (between-years) changes in the density of the studied populations.