Date of Award
Doctor of Philosophy
Ecology, Evolution, and Organismal Biology
Ecology and Evolutionary Biology
W. Stanley Harpole
Brent J. Danielson
Plant reproduction and dispersal are important life history factors that influence fitness and spatial survival. Despite the importance of these factors, little is known about how the maternal resource environment, or co-existing biotic herbivores influences these factors in grassland communities. For my dissertation I investigated how the herbivore community (top-down factors) and the addition of soil resources (bottom-up factors) influenced plant reproduction and dispersal. I found that nutrient additions had a stronger impact on the reproductive response of grassland communities than the seedling, or vegetative response. The trends in the reproductive response also varied by functional group. Perennial plants with slow vegetative spread decreasing reproductive abundance with nutrient additions, while perennial plants with rapid, rhizomatous spread increased reproductive abundance with nutrient additions. I also found that the addition of nutrients influenced dispersal traits across three sites within the tallgrass prairie region of the midwestern United States. Nutrient additions affected the height at seed release, and the number of seeds produced per individual, but the direction of these trends were species, and sometimes site, specific. The alterations in height at seed release translated to a simultaneous increase or a decrease in potential dispersal distance. Finally, I found that herbivores can alter the invasion rates of establishing grassland communities by decreasing both the population size, and movement ability of established seedlings. My work points to the importance of understanding intra-specific response to different biotic and abiotic conditions for predicting spatial dynamics in grassland systems.
Lauren Lavins Sullivan
Sullivan, Lauren Lavins, "Top-down and bottom-up effects on plant reproduction and dispersal in grassland systems" (2014). Graduate Theses and Dissertations. 14298.