Population and community responses to landscape change in Kansas grasslands

Recurrent and episodic disturbance affect the structure and diversity of communities, species movements and competitive and trophic interactions. In this dissertation I explore both direct and indirect effects of three major forms of disturbance (fire, habitat fragmentation and major herbivore outbreaks) on communities in eastern Kansas.; At Konza Prairie Biological Station I studied the effects of prairie fires and their frequency on ground beetles (Coleoptera: Carabidae), through extensive pitfall trapping. Patterns of local diversity were consistent with expectations of Connell's intermediate disturbance hypothesis, which predicts a community to exhibit the highest diversity at some intermediate interval following disturbance. Fires caused no detectable population movements immediately following the disturbance event, but species richness in the eight weeks following fire may be slightly elevated in burned landscape units compared to adjacent unburned units. Additional work suggested that landscape heterogeneity in microhabitat also affects beetle communities via variation in dominant plant group.; At the Kansas Field Station and Ecological Reserves I studied the application of island biogeography theory to patterns of plant diversity under conditions of experimental habitat fragmentation. In general I found observed patterns consistent with expectations of reduced diversity with increased fragmentation, although some of these patterns were delayed in time, and statistical compensation for an artifact (the possibility that focal species may live between isolated habitat patches) may be necessary. I also document that spatial patterning of an insect outbreak (periodical cicadas) can be affected by the characteristics of a landscape formed by habitat fragmentation. Spatial data available at our site was more detailed than those of comparable studies, leading to greater understanding of the interplay between different landscape parameters and their impacts on disturbance. Finally, I expected this patterning to affect trophic impacts of the emergence, but find evidence for this.; Overall, my results confirm that fire and habitat fragmentation have powerful effects on patterns of local species diversity and composition, and that these effects can be complex and may only enfold following time lags. This work serves to increase understanding of the relationship between disturbance regimes, spatial patterning of the environment, and attributes of biological communities.