Master of Science, The Ohio State University, 2020, Environment and Natural Resources

Urbanization can have profound influences shaping patterns of songbird diversity. For many species, urbanization poses considerable challenges, yet in many instances urban areas provide important habitat for songbirds, most notably riparian urban areas. With renewed interest to maintain functioning urban forests, understanding the interactions between songbirds and their urban environments is critical to making informed land management decisions. My research addresses habitat usage of breeding urban songbirds in Columbus, Ohio, focusing on the relationship between urban songbird presence and behavior and the vegetation in urban riparian forests. Previous songbird studies have been conducted in the Columbus metropolitan area since 2001 and have focused primarily on the impacts of urbanization on abundance, nesting, and survival. My goals for this study were to add to this knowledge base by examining potential correlations between songbird territory density and structural vegetative characteristics in urban forests and to investigate the foraging strategies of urban songbirds. The first component of my study examines the relationship between the breeding territory densities of individual songbird species and the vegetation structure of urban sites. Given that vegetation structure has been linked to urban songbird abundance and survival, the number of trees, the size of trees, and the density of exotic or native stems in a site may influence the territory density of certain species. I tested the hypotheses that overall songbird territory density will be greater in areas will fewer exotic stems and Neotropical territory density will increase with structural diversity. I conducted spot maps in urban riparian forests in Columbus, Ohio from late April to August in 2019 and compared these data to spot maps conducted by my colleagues in 2007 and 2011 to determine territory densities for the most common species, which included the Blue-gray Gnatcatcher, Blue Jay, Carolina (open full item for complete abstract)

Committee: Stephen Matthews PhD (Advisor); G. Matthew Davies PhD (Committee Member); Charles Flower PhD (Committee Member); Christopher Tonra PhD (Committee Member) Subjects: Urban Forestry; Wildlife Conservation; Wildlife Management

Master of Science, University of Akron, 2014, Biology

Temperate forests of North America are being altered by the combined effects of two ecosystem engineers: white-tailed deer, Odocoileus virginianus, and exotic earthworm species from Europe and Asia. The intense pressure of herbivory from white-tailed deer alters the structure, abundance and diversity of plants in the forest understory. Exotic earthworm invasion can dramatically change the physical and chemical attributes of forest soils, altering plant-soil interactions which can facilitate changes in understory plant communities. Here we have used a deer exclosure study to isolate the impacts of white-tailed deer from those of exotic earthworms in order to better understand how they interact in shaping temperate forest plant communities. Results confirm that deer can dramatically reduce the abundance, richness and diversity of native plants. Contrary to past studies we found no evidence that exotic earthworms themselves reduce native plant abundance or diversity. Exotic earthworms are shown to alter the plant community through the loss of specialist species which are replaced by generalist and exotic species. This is the first in situ study of exotic earthworms in temperate forests to account for deer impacts and identify the unique and aspects of exotic earthworm on forest plant communities. The combined effects of these engineering species can dramatically alter the forest plant community and pose a formidable threat to the conservation of biodiversity.

Committee: Randall Mitchell Dr. (Advisor); Gregory Smith Dr. (Advisor); Maatthew Shawkey Dr. (Committee Member) Subjects: Biology; Ecology; Forestry

Master of Science, University of Toledo, 2010, Biology (Ecology)

Extracellular enzymes are produced by both microbes and plants and directly mediate organic matter breakdown. These enzymes can be present on root surfaces or secreted by roots into the rhizosphere and are used to exploit pools of organic nutrients in the soil. Extracellular enzymes secreted by plant roots have received little attention outside of a few studies examining enzyme production on a small scale or in artificial/intensely managed environments. As a result, little is known about the extent of root enzyme activity and the degree to which these enzymes can be used by roots to exploit pools of organic nutrients in the soil. Additionally, comparative studies between native and invasive exotic plant root extracellular enzyme capabilities are lacking. To address these knowledge gaps, the objective of this study was to characterize the activities of a variety of nitrogen and phosphorus acquiring enzymes on the roots of a diverse range of native and invasive exotic plants. High rates of phosphatase and chitinase activity were observed on the roots of all plant sampled compared to the surrounding soil. Rates of root phosphatase activity were the highest ever recorded in our laboratory, even exceeding rates of 14,000 nmol/h/g on roots of the non-mycorrhizal invasive herb Alliaria petiolata (garlic mustard). Roots were also examined for two types of peptidases, leucine amino peptidase and glycine amino peptidase. No roots had any significant glycine amino peptidase activity, while a small proportion exhibited relatively low rates of leucine amino peptidase activity. Regressions comparing nutrient levels and enzyme activity showed no significance, but a few significant relationships were observed with the plants Lonicera maackii (honeysuckle), Acer rubrum (red maple), and A. petiolata. Comparing invasive exotic and native plants yielded no significant comparisons save that A. petiolata again had significantly higher leucine amino peptidase and phosphatase activity than (open full item for complete abstract)

Committee: Michael Weintraub (Advisor); Elliot Tramer (Committee Member); Scott Leisner (Committee Member) Subjects: Botany; Ecology; Environmental Science

Doctor of Philosophy, The Ohio State University, 2009, Evolution, Ecology, and Organismal Biology

Mixed-oak (Quercus ssp.) forests in southern Ohio have been significantly affected by fire suppression policies enforced since the early1920s, possibly altering key ecosystem properties such as soil organic matter quality and quantity, nutrient availability, and microbial activity. The Fire and Fire Surrogate (FFS) program is a multidisciplinary program that included the experimental application of both functional restoration treatments (i.e. prescribed fire at historical intervals) and structural approaches (i.e mechanical thinning to pre-settlement density and species composition). Within that framework, I focused in three unquantified major aspects of southern Ohio forest ecosystems exposed to a quasi-natural disturbance regime: (1) effects on soil microbial communities, (2) possible belowground effects of non-native earthworm species, and (3) impacts on the rates of litter decomposition and subsequent nutrient release. Direct effects of prescribed fire and thinning in soil nutrient dynamics and microbial communities were analyzed three months after the second application of prescribed fire. This short-term analysis was complementary to a series of in-situ, manipulative experiments that evaluated (a) potential effects of non-native earthworm species on N dynamics, as well as changes in soil organic matter and microbial communities within the FFS experimental design, and (b) litterbag incubations of native leaf mixtures and standard litters over more than three years in our study sites, where I evaluated the influence of restoration treatment, leaf litter quality, and landscape position on leaf litter decomposition processes and nutrient release. The major conclusion of my studies is that I did not observe definitive effects of restoration treatments. Rather, a combination of site characteristics and landscape position were responsible for some of the differences observed when comparing unmanaged controls to any of the alternative restoration treatments. I hypoth (open full item for complete abstract)

Committee: Raph Boerner PhD (Advisor); Clive Edwards PhD (Committee Member); Robert Klips PhD (Committee Member); David Stetson PhD (Committee Member); Mac Callaham Jr/PhD (Committee Member) Subjects: Ecology; Forestry

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2012, Biological Sciences

Oak savannas of the Midwestern U.S. are among the most imperiled North American plant communities. The 478-km2 Oak Openings region of Northwestern Ohio is one of the few landscape-scale savanna systems remaining in the Midwest. Despite conversion of large portions of the Oak Openings for human land uses, the region still supports high levels of floristic diversity. However, regional patterns of Oak Openings plant diversity within the modern landscape are not well understood. My research objectives were 1) to determine the current extent and distribution of Oak Openings plant communities, 2) to quantify multiscale patterns of plant species richness within the context of the surrounding landscape, and 3) to build predictive species distribution models of rare plants to evaluate regional patterns in habitat suitability. First, using multi-seasonal Landsat images, I determined that <3% of the Oak Openings remains covered by native savannas, prairies, and barrens, while three-fourths of the region has been converted for urban, residential, and agricultural uses. Second, using measures of spatial heterogeneity derived from field data and remote sensing, I developed models of native and exotic plant species richness at two spatial extents and at four ecological levels for the Oak Openings. These models consistently explained more variation in exotic richness (better explained at the larger spatial extent) than in native richness (better explained at the smaller spatial extent). At all ecological levels, percentage of human-modified land cover in the surrounding landscape (negatively correlated with native richness, positively correlated with exotic richness) was a strong predictor of species richness. Finally, I developed species distribution models for nine rare plant species within the Oak Openings region using the Maxent modeling algorithm. Proportional land cover surrounding species occurrences accounted for a large proportion of the predictive power of all models. As (open full item for complete abstract)

Committee: Karen V. Root PhD (Advisor); Enrique Gomezdelcampo PhD (Committee Member); Helen J. Michaels PhD (Committee Member); Jeffery G. Miner PhD (Committee Member); Robert K. Vincent PhD (Committee Member) Subjects: Biology; Ecology; Natural Resource Management

Master of Science in Environmental Science, Cleveland State University, 2013, College of Sciences and Health Professions

No native earthworms exist in the Great Lakes region of Ohio. All earthworms found in previously glaciated areas of the United States either migrated from unglaciated areas or were introduced as a result of human activities such as agriculture and sport fishing. Non-native earthworms may facilitate dramatic changes in structure and function of plant and invertebrate communities of forest ecosystems. This study examined how the presence of non-native earthworms within the Cleveland Metroparks may correspond with plant and soil invertebrate communities. Special attention was given to the Asian earthworm, Amynthas spp., a recent arrival to northeastern Ohio and a particularly aggressive colonizer. Earthworms and leaf litter were sampled at a set of well-characterized study plots. Length-based allometric equations available in the literature were applied to measure earthworm biomass of most species, and here a new equation for Amynthas was derived. A computer-based method was used to measure length and required less time and effort and produced values of significantly lower variability than the traditional ruler method. Higher abundances and biomasses of earthworms were associated with degraded plant communities. Although decreased litter mass correlated with greater earthworm activity, invertebrate communities were not degraded; in fact there appeared to be a modest beneficial effect. Earthworm activity changed soil chemistry as demonstrated by selective decreases in soil carbon, nitrogen, and phosphorus. Soil composition also affected earthworm communities as low pH favored an acid–tolerant species and was associated with moderate earthworm densities. A strong negative interaction between abundances of Amynthas and those of other exotic earthworms was found, yet Amynthas did not exert a distinctive influence upon plant or invertebrate communities.

Committee: Bernard Walton Ph.D. (Committee Chair); Yung-Tse Hung Ph.D. (Committee Member); Robert Krebs Ph.D. (Committee Member); Julie Wolin Ph.D. (Committee Member) Subjects: Ecology; Environmental Science