Date on Master's Thesis/Doctoral Dissertation

5-2023

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Emery, Sarah

Committee Co-Chair (if applicable)

Flory, S. Luke

Committee Member

Flory, S. Luke

Committee Member

Yanoviak, Steve

Committee Member

Masters, Jeffrey Alan

Committee Member

Day, C. Andrew

Author's Keywords

invasion ecology; mycorrhiza; forestry; GIS

Abstract

Forest managers face multiple challenges in maintaining woodland systems, including climate change, habitat destruction and fragmentation, and the invasion of novel species. Invaders can change microclimates, alter nutrient cycling and understory habitat, and outcompete native species, leading to native species population declines and reduction in species richness. To effectively combat plant invasions it is necessary to first understand factors contributing to invasive species spread, including the complex interactions between invaders and native biota. This dissertation investigates the abiotic conditions and biotic interactions associated with invasion success of the non-native grass Microstegium vimineum, which is a species of great concern for forest managers throughout the eastern US. My initial study identified the most important abiotic elements associated with Microstegium presence. I found light availability and soil moisture to be the strongest predictors of Microstegium cover, followed by soil nitrogen and soil phosphorous. In this study I also examined the relationship between Microstegium and soil arbuscular mycorrhizae. I found no differences in abundance of soil mycorrhizae between invaded and noninvaded areas, and no difference in root colonization of Microstegium across abiotic gradients. My second study analyzed the germination and growth of Microstegium, native grasses, and native woody species in field soils associated with Microstegium invasion. I found that Microstegium-associated soils enhanced Microstegium seed germination, while inhibiting the germination of native grass species. Surprisingly, I found greater aboveground biomass and stem height of native woody species in Microstegium-associated soils; however, I also found increased seedling mortality in Microstegium-associated soils. For my final study, I surveyed Microstegium invasion at the landscape scale in seven local nature reserves to create a habitat suitability analysis using Geographic Information System (GIS) processing. I combined various habitat variables indicative of Microstegium presence to identify areas of greatest habitat suitability. These findings can inform best practices for prevention and eradication of Microstegium. For example, the creation of a habitat suitability analysis for a nature reserve, coupled with the knowledge of the importance of various abiotic factors to Microstegium presence, can assist land managers to direct limited resources to areas of highest susceptibility to invasion or to mitigate population spread.

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