9615136 Fowler This study addresses one of the core questions of population biology: What determines the numbers of individuals of a species in a natural or semi-natural ecosystem? Using an existing 15-year data set, a set of analytical and simulation models will be constructed, validated, and analyzed to answer this question for a native plant species, Texas gramagrass. Part of answering the broader question will be determining the extent to which population size and structure is effectively regulated; another part will be determining the way in which that regulation operates. The models will incorporate the effects of neighboring plants on each other, the spatial arrangement of the plants, differences in plant size, and variation over time in all variables, as all of these factors are likely to be important. Although only a single species will be studied, the information obtained about this species' population dynamics will provide insights into the population dynamics of many other plant species, some of which are invasive weeds, endangered species, or, like the study species, economically important range grasses. A better understanding of plant population regulation will contribute to efforts to manage weeds, to preserve rare and endangered species, to predict the effects of grazers and herbivorous insects upon particular plant species, and in general to understand and manage plant species and communities. In addition, the population models to be developed in this study can be easily modified to be of general use.
