9207376 Glenn Species diversity in a community is partially a product of the dynamics of local immigration and extinction. Barriers to immigration may result in shifts in dominance and affect community structure and function. Percolation theory provides a mechanism for developing hypotheses regarding movement of organisms through the environment. Community structure in grasslands resembles a percolation network, however, the applicability of percolation network, however, the applicability of percolation theory to plant community structure has not been evaluated. A series of hypotheses will be tested using field experiments and simulation modeling to determine the applicability of percolation theory to predicting spatial patterns of dominance and diversity in grassland vegetation. Previous studies have shown grasslands to be highly dynamic at small spatial scales over short periods. Preliminary results from stimulation models of clonal growth in percolation networks suggests that species diversity is affected by barriers to movement. Above a critical threshold, species diversity declined in these models as superior competitors dominated available space. A series of experimental percolation networks in grassland vegetation will be created and clonal growth of prennial species, local patterns of immigration and extinction, species diversity, and spatial pattern will be monitored. Field experiments will be supplemented by modelling percolation of clonal plants with different rates of spread and competitive abilities. This study will help to determine the utility of percolation theory to small-scale plant comm unity dynamics in grassland vegetation. ! ! ! F ( Times New Roman Symbol & Arial " h Y C abstract Elizabeth M. Behrens Elizabeth M. Behrens
