Doctor of Philosophy (PhD), Ohio University, 2020, Plant Biology (Arts and Sciences)

Human activities have greatly impacted terrestrial ecosystems through various forms of habitat modification including the creation of powerline corridors. The routine maintenance of powerline corridors to prevent vegetation interference with electricity transmission lines leads to the emergence of early successional vegetation surrounded by a forest matrix. An analogous situation emerges in the creation of openings for wildlife management purposes. To determine the ecological consequences of human-modified landscapes, I investigated the effect of environmental gradients generated by these landscape modifications on floristic composition. I also examined edge effects along three powerline corridors with different management histories and investigated pollination dynamics of goldenrod Solidago canadensis within a powerline corridor and around wildlife openings. Powerline corridor habitat had more species and greater Shannon diversity than adjacent forest habitat. Powerline corridor and adjoining forest habitat had 69% mean Jaccard similarity coefficient, and species richness declined sharply within 10 m from the corridor edge. Invasive plants were more abundant within powerline corridor, along powerline corridor edges, and along wildlife opening edges compared to forest habitat. More frequent disturbance at wildlife openings facilitated recolonization by other insect-pollinated plants, which meant that some goldenrod patches there experienced more pollinator visits compared to those within powerline corridors. However, pollen viability and amount of fruit set did not differ between the two landscape elements. This work further strengthens the case of managing for biodiversity within powerline corridors as evidenced by greater species richness and pollination dynamics within this human-modified landscape.

Committee: Brian McCarthy (Advisor); Glenn Matlack (Committee Member); Jared DeForest (Committee Member); James Dyer (Other) Subjects: Ecology; Plant Biology

MS, Kent State University, 2019, College of Arts and Sciences / Department of Biological Sciences

Land managers across the Appalachian region have been dissatisfied with the progress of native temperate forest regeneration on surface mines reclaimed under Surface Mining Control and Reclamation Act of 1977 (SMCRA) protocols. These sites are commonly colonized by invasive plant species and have inadequate soils. Many of the nearly 50 former surface mines located within Cuyahoga Valley National Park (CVNP), Ohio, underwent reclamation following SMCRA protocols as an effort to restore native forest habitat, but park staff have also found succession to occur at a far slower rate than originally anticipated. While many studies have been conducted on acidic coal mines, reclaimed sites in CVNP were mined for non-coal resources and are alkaline. Here I investigated the plant communities and soil chemistry of reclaimed surface mines in CVNP to determine the implications of SMCRA protocols on the landscape on sites with alkaline soils. First, I analyzed how vegetative communities on reclaimed surface mines at CVNP changed over a 28-year chronosequence with particular regard to woody species and invasive species. Natural succession of sites was occurring slower than park staff anticipated, as the presence of woody species did not increase significantly over time. However, this did not appear to be a result of invasive plant colonization because exotic plant presence decreased over time, pointing toward inadequate soil conditions rather than interactions among the plant community withholding the growth of woody species. Results imply that SMCRA reclamation protocols do not improve site conditions sufficiently to facilitate natural succession as a tool to return native forests to mines within the timeframe envisioned by land managers. Second, I observed the effects of early colonization of woody nitrogen (N) fixing individuals on soil nutrient concentrations and vegetative communities at the mines. I compared an invasive N-fixing species, autumn olive (Elaeagnus umbel (open full item for complete abstract)

Committee: Chris Blackwood Ph.D. (Advisor); David Ward Ph.D. (Committee Member); Oscar Rocha Ph.D. (Committee Member) Subjects: Ecology

Doctor of Philosophy, The Ohio State University, 2019, Evolution, Ecology and Organismal Biology

The drivers of plant diversity and community composition are often influenced by deterministic mechanisms, such as existing environmental conditions, including landscape-level topographic features. In addition, evidence suggests that stochastic mechanisms can also play a critical role in plant community assemblage. Therefore, I investigated how diversity and composition are distributed through space in a mid- successional mixed hardwood forest in northern lower Michigan, USA. This region has been heavily influenced by its glacial past, which resulted in geographically and abiotically distinct glacial landforms that have been shown to influence spatial dynamics of forest communities. Vegetation sampling plots (n=87) were established at the University of Michigan Biological Station (UMBS). Vegetation data of the overstory (>9cm dbh), sapling (1.5-9cm dbh) and groundcover (% cover) layers were collected. Abiotic variables, including elevation, pH, and soil nutrients, were collected in a subset of plots (n=40). I conducted various multivariate statistical analyses to assess the difference in plant communities and abiotic condition, including ANOVA, Variation Partitioning, PERMANOVA, NMDS, and RDA. Variation Partitioning results demonstrated that both deterministic and stochastic mechanisms influenced the community composition of all vegetation layers, however the overstory was mostly influenced by stochastic mechanisms, while the sapling and groundcover layers were opposite. ANOVA results showed strong differences in diversity between glacial landforms. Additionally, PERMANOVA and Non-metric Multidimensional Scaling (NMDS) showed strong differences in community composition between the glacial landforms. Redundancy Analysis (RDA) revealed a strong influence of abiotic variables on composition, with the strongest effects coming from elevation and O horizon depth (O_depth). My findings indicate a large influence of glacial landforms on the production and maintenance of loc (open full item for complete abstract)

Committee: Peter Curtis (Advisor); Maria Miriti (Committee Member); Stephen Hovick (Committee Member); Luke Wilson (Other) Subjects: Ecology; Plant Biology

Doctor of Philosophy, The Ohio State University, 2012, Horticulture and Crop Science

Invasions by exotic insect pests and pathogens have been devastating North American forests for decades. Presently, emerald ash borer (EAB; Agrilus planipennis) is devastating populations of native ash (Fraxinus species) trees throughout eastern North America. Disturbances, such as canopy gap formation due to EAB-induced ash mortality, alter availability of resources including light, water, and mineral nutrients, potentially resulting in shifts in plant community composition. Following the loss of nearly all reproductively mature trees, ash regeneration was effectively eliminated, and the “orphaned cohort” of ash in the seedling layer represents the potential for persistence of ash in EAB-impacted forests. Hemispherical photographs, used to calculate percent gap fraction, were taken at a height of 1.5 m to determine how loss of ash was affecting radiant energy resources available to the understory vegetation. Variation among gap fraction values indicated high heterogeneity in light reaching the forest understory. Percent gap fraction was negatively correlated with percent plant cover within the 2 – 5 m and > 5 m layers, suggesting that while gaps may have formed in the canopy layer, light was intercepted before reaching the forest understory. Plant abundance and composition within the forest understory did not change dramatically during the course of the study, nor was there a direct connection between species abundance or diversity and gap fraction. Plant communities were slightly differentiated by the soil hydrological conditions, and less diverse communities occurred in mesic and xeric sites than in hydric sites. Growth of invasive and native species in the understory was not influenced by percent gap fraction; invasive species typically outgrew native species regardless of light level and soil hydrological condition. In a comparison of emergence and survival of Lonicera maackii and Rosa multiflora under various native and invasive leaf litters we found no differ (open full item for complete abstract)

Committee: John Cardina PhD (Advisor); Daniel A. Herms PhD (Committee Member); P. Charles Goebel PhD (Committee Member); Kathleen S. Knight PhD (Committee Member); Emilie E. Regnier PhD (Committee Member) Subjects: Biology; Botany; Conservation; Ecology; Forestry