| dc.description.abstract | White-tailed deer (Odocoileus virginianus) abundance is increasing across North America as habitat is created and populations are protected from predation. Their preferred habitat, the forest edge, surrounds many remnant prairie fragments, providing access to small plant populations that may be sensitive to deer herbivory. This thesis investigated the effects of deer herbivory on plant communities in tallgrass prairie remnants as well as the perennial Helianthus species contained therein. In the community-focused study, I found that white-tailed deer exclusion from study plots over two years led to reduced herbivory but did not change the overall richness, diversity, or community composition of the sites. The edge and interior prairie plots contained distinctly different plant communities, and the edge plots experienced greater counts of herbivory on favored species than the interior plots. Woody species abundance was reduced by deer herbivory, a potentially important result given the effects of woody plant colonization on prairie fragments. Helianthus herbivory was higher at the edge of the prairie than in the interior. These latter results led to a more focused study of deer herbivory on Helianthus using two study methods: exclusion of deer in the prairie and artificial herbivory on stems off site. White-tailed deer remove the apical meristem from plants, often causing the plant to branch. Branching may lead to the production of multiple inflorescences, possibly providing a reproductive benefit through overcompensation. These studies investigate Helianthus response to herbivory to determine if the effect on the plant’s fitness is negative or positive, overall. In the prairie study, stems protected from herbivory were taller and less likely to branch than those exposed to deer herbivory. Helianthus in the exclosures were more likely to produce inflorescences, but there was no difference in the number of inflorescences produced by protected vs. damaged reproductive stems. The same general conclusions were drawn from the artificial herbivory study. However, the herbivory treatment was imposed across the entire rhizome on all stems produced by the plant. In this study, rhizomes with herbivory grew more branches per stem than undamaged rhizomes. Still, there was no evidence of increased reproduction in damaged plants. Thus, deer herbivory may alter the morphology and reproduction of perennial Helianthus, potentially having a long-term effect on their abundance in plant communities. Continuing both studies would reveal the long-term effect of deer herbivory on both prairie plant communities and the population dynamics of individual species. Continued increase of white-tailed deer populations may pose a threat to favored browse species in fragmented plant communities. However, herbivory may play an important role in succession in grasslands. As conservationists consider the management of white-tailed deer in protection of remnant ecosystems, it will be important to consider both the positive and negative effects of herbivory. | |
