LANDSCAPE FRAGMENTATION AND DISPERSAL IN A MODEL OF RIPARIAN FOREST DYNAMICS

Although several computer simulation models of forest tree growth have been developed at the stand level, they do not address the impact of mainland landscape structure and forest fragmentation on the forest dynamics of spatially extensive areas. To model forest dynamics at the landscape level, a model must explicity consider the dispersibility of tree species within the landscape. A computer simulation model, seedflo, is constructed which models tree species dispersal based on empirical evidence. The analyses test the hypothesis that a model with seed dispersal differs in its projections from a model that assumes ubiquitous dispersal. For species in a riparian corridor, seedflo projects lower diversity in more fragmented landscapes and increases the abundance of those species with higher dispersal probabilities, especially bird-dispersed species, and toward species with average dispersal abilities which normally compete with species with low dispersal probabilities. The effects of considering landscape fragmentation and dispersal are amplified when environmental stress, in this case flooding, is increased. The results conform to theoretical expectations and indicate that seed dispersal should be incorporated in landscape simulation models. © 1990.