Understanding the distribution and abundance of species both within and between communities has been one of the primary goals in community ecology. Although much research has focused on within community patterns, there has been a new emphasis on factors associated with regional distribution and abundance. Recently, Hanski (1982) proposed a dynamic regional distribution model based on island biogeography from which he derived the core-satellite hypothesis. The core-satellite hypothesis predicts a bimodal frequency distribution in which species tend to occur at all similar sights in a region (core species) or they tend towards extinction (satellite species). This model contrasts with others which predict a unimodal distribution of species in a region. This project will test the unique aspects of Hanski's model in comparison to other models (Levins 1969, Brown 1984) by analyzing and adding to plant distribution data from the Konza Prairie Long-term Ecological Research Site. General questions include: is the regional distribution of plant species bimodal? Do species shift from core to satellite categories and vice versa? Does grazing effect the pattern of bimodality in plant communities? Preliminary research indicates that prairie vegetation is dynamic over the short term, and that species regional and temporal distributions are bimodal as predicted by the core- satellite model. This project will provide the first real test of this important model using spatial and temporal data, in combination with a large-scale field experiment from a single site. A suite of plant surveys will augment long-term distributional data on prairie plants, and provide the primary basis for model testing. Data generated as part of large-scale trails on grazing and fire disturbance will provide a unique opportunity to validate the model experimentally and test the role of intermediate levels of disturbance inustructuring plant communities. Overall, this research has clear implications for understanding factors affecting the structure, dynamics, and distribution of plant species within and between grassland communities.
