Date of Award
Ph.D. in Biological Science
J. Stephen Brewer
Clifford A. Ochs
Jason D. Hoeksema
University of Mississippi
Previous work has shown that ecological communities with high species diversity are resistant to invasion, but evidence is lacking in woodland restoration conditions with native groundcover and oak species for the competitively superior invader: Microstegium vimineum. I addressed the following questions: (1) Does diversity-mediated competitive resistance resist invasion by M. vimineum, and what is the competitive effect of M. vimineum on resident plant diversity? (2) How do aboveground and soil-mediated competitive effects of M. vimineum influence survival of two perennial forbs at two sites of different M. vimineum productivity? (3) Are there species differences in acorn supply and seed removal, and does competition from native and invasive vegetation impact oak seedling survival? I addressed the first question by examining the influence of diversity-reduction treatments on native species and density-reduction treatments on M. vimineum. Neither rare species removal nor dominant species reduction significantly increased M. vimineum density. Herbicide application dramatically reduced M. vimineum in year two, but not the majority of resident plants. To address the second question, I examined aboveground and soil-mediated competitive effects of M. vimineum on two native perennial herbs using a field experiment between two sites with different productivity. I found that aboveground and soil-mediated competition interacted to reduce transplant survival at the more productive site. To address the third question, I investigated acorn supply between two species, and influence of M. vimineum on acorn removal rates and seedling survival. Viable acorn density differed by species and year. M. vimineum patches reduced the survival of both oaks. Neighbor removal increased oak seedling survival, but did not differ by patch type. This suggests soil-mediated effects remain present after invasive removal. These effects can interact with increased aboveground competition at productive sites to reduce native survival. I found no evidence that diversity-mediated resistance deters invasion by a highly competitive invader. I suggest lower acorn supply and survival of Quercus stellata, especially within M. vimineum patches, may contribute to the lower regeneration rates compared to Quercus alba. For M. vimineum, it would appear that nearly complete removal of this invader is necessary to preserve plant species diversity in this system.
Williams, Griffin L., "Mechanisms and Consequences of Competition between Microstegium vimineum and Native Plants and Their Relevance to Invasion Theory and Oak Woodland Restoration" (2023). Electronic Theses and Dissertations. 2598.
Available for download on Friday, September 13, 2024