Master of Science (MS), Bowling Green State University, 2020, Biological Sciences

Introduced to the Great Lakes Region from Europe before 1900, invasive Butomus umbellatus (Flowering rush) forms monotypic stands that crowd native species and cover open water systems across Great Lakes shorelines and reservoirs in the northern US. Factors contributing to invasion persistence and impacts on ecosystem function by this species are poorly understood. This study characterizes vegetation and environmental factors at the Ottawa National Wildlife Refuge, which borders Lake Erie, to understand how sediment nutrient levels in watersheds affect B. umbellatus invasion. We hypothesized that increased sediment nutrient levels are important drivers of B. umbellatus invasion success. Sediment nutrient levels, matter, water depth, and vegetation were sampled within 1m2 plots throughout the management units of the marsh complex. Vegetation of B. umbellatus and 18 other species present were harvested or canopy characteristics measured to estimate biomass. B. umbellatus was the most abundant of all identified emergent invasive species found, occurring at 55 % of the surveyed plots. B. umbellatus rhizome bud count averaged 509 per plot, with a range of 0 – 2760 buds. While sediment nutrient analysis of nitrogen and phosphorus showed heterogeneity within and across management units, nutrient levels did not predict B. umbellatus abundance. However, B. umbellatus biomass decreased with increasing community biomass. Vegetative propagule production via rhizome buds decreased with increased nutrients and increased community biomass. B. umbellatus was found to have a wide range of nitrogen and phosphorus in leaf tissue, and 2 – 4 times more average phosphorus than all analyzed native species. This data will assist managers in identifying timing and approaches for controlling this invasive species and restoring wetland biodiversity.

Committee: Helen Michaels PhD (Advisor); Andrew Gregory PhD (Committee Member); Kevin McCluney PhD (Committee Member); Angélica Vázquez-Ortega PhD (Committee Member) Subjects: Biology

Bachelor of Science, Wittenberg University, 2023, Biology

This study investigates the soil quality and plant diversity of a discontinued golf course in Springfield, Ohio, with the aim of assessing its potential for restoration. Led by the National Trail Parks & Recreation District, the restoration plans for Snyder Park include the establishment of wet meadows, prairies, and woodlands, which can thrive in the natural hydric soils of the former golf course. In this study, baseline soil data was collected using GIS and GPS technologies, analyzing soil texture, carbon content, nitrate nitrogen, phosphorous, potassium, replaceable calcium, humus, and pH. Plant diversity was evaluated through random sampling of quadrats. Initial observations revealed patches dominated by specific plant species, and a comparison of soil and plant characteristics across elevations was conducted. The golf course mainly consisted of the Westland soil series, which supports water retention. However, deficiencies in humus and low levels of potassium and nitrate nitrogen pose challenges for restoration. Limited native plant species adapted to moist conditions were observed, suggesting ongoing recovery from intensive land management. To sustain a natural wetland or floodplain ecosystem, restoration efforts should focus on introducing native wetland species and providing nutrient inputs, mainly nitrogen and potassium. The Snyder Park golf course holds potential for restoration, but additional measures are necessary for a successful habitat transition.

Committee: John Ritter (Advisor); Nona Moskowitz (Committee Member); Matthew Collier (Committee Member) Subjects: Ecology; Environmental Science; Environmental Studies; Horticulture; Soil Sciences

Doctor of Philosophy (PhD), Wright State University, 2022, Environmental Sciences PhD

Disturbances in environment can lead to a wide range of host physiological responses. These responses can either allow hosts to adjust to new conditions in their environment or can reduce their survival, and can subsequently cause host traits to shift. Small mammals are particularly vulnerable to stochastic disturbances, like a pathogen introduction, because of their high energy demands. Studies examining host responses to pathogens often focus on species highly susceptible to infection that typically have high mortality rates, leading to a gap in understanding the responses of less susceptible species. My dissertation evaluates the energy balance of Eptesicus fuscus (big brown bats), a species considered less susceptible to the introduced fungal pathogen Pseudogymnoascus destructans (Pd) which causes white-nose syndrome in North American hibernating bats. I quantified changes in body mass, energy expenditures and the abundance of E. fuscus over long-term Pd exposure time. Using 30 years of data for 24,129 individual E. fuscus captures across the eastern US, I found E. fuscus body mass decreased with increasing latitude once Pd was established on the landscape (5+ years). When measuring whole-animal energy expenditures of 19 E. fuscus in lab settings using open-flow respirometry, I found that E. fuscus with long-term exposure to Pd have increases or no change to torpid metabolic rates across a wide range of ambient temperatures. Finally, the overall abundance of E. fuscus increased with Pd exposure, and lactating and post-lactating bats increased abundance with increasing latitude in the eastern US. Taken together, these results suggest that E. fuscus may have a combination of pathogen and intraspecific competitive pressures impacting their populations, particularly in northern latitudes. This dissertation highlights how introduced pathogens can cause spatially variable responses in less susceptible hosts over time, and other ecological pressures may contribute t (open full item for complete abstract)

Committee: Megan Rúa Ph.D. (Committee Co-Chair); Lynn Hartzler Ph.D. (Committee Co-Chair); Joe Johnson Ph.D. (Committee Member); Lisa Cooper Ph.D. (Committee Member); Volker Bahn Ph.D. (Committee Member) Subjects: Biology; Ecology; Environmental Science; Physiology; Wildlife Conservation

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Biological Sciences

The eastern redcedar Juniperus virginiana is the most widespread conifer in the eastern United States, and can be found in every state east of the 100th meridian. This tree is encroaching into new habitats and old fields in the western states, as far as Nebraska and South Dakota. J. virginiana can survive and thrive in adverse conditions and extreme environments. We were interested in testing the effects of biotic and abiotic conditions on J. virginiana ecophysiology. We investigated the role of competition and soil substrates in a greenhouse experiment, and in a series of field experiments, we tested a stress-gradient approach on abiotic stress and intraspecific competition, the role of different soil types on local adaptation of two J. virginiana varieties, and the effects of tree size and season on J. virginiana performance and ecophysiology. We found that there was a strong effect of competition with grass (Bromus inermis) but not with post oak (Quercus stellata). In addition, fertilizer had a greater effect than lime on J. virginiana performance, indicating that J. virginiana tolerates rather than prefers limestone soil to avoid competition with other tree competitors. We also found support for Walter's two-layer hypothesis in which there was root partitioning between the J. virginiana and smooth brome grass. Similarly, we also found root partitioning and differentiation between the J. virginiana and post oak, due to root length differences. In our stress-gradient experiment, we found that the population at the site furthest from Lake Erie and with the highest soil nutrients had greater physiological activity and total biomass, which supported our predictions. Intraspecific competition was not an important factor affecting J. virginiana performance. Surprisingly, the intermediate site had the lowest overall performance and lowest water stress, due to poor drainage, indicating that more parameters need to be considered when setting up a stress-gradient experime (open full item for complete abstract)

Committee: David Ward (Advisor); Emily Rauschert (Committee Member); Oscar Rocha (Committee Member); Juliana Medeiros (Advisor) Subjects: Biology; Climate Change; Ecology; Plant Biology; Plant Sciences

Doctor of Philosophy, The Ohio State University, 2021, Entomology

The majority of the human population resides in cities. This transformation to an urbanized world has disrupted many species due to habitat disturbance, alien species colonization, and changes in soil and air quality. This reality has raised concerns about the impact of urbanization on insect communities. Many cities are implementing conservation efforts to combat these stressors by transforming habitats to urban farms, pocket prairies, and rain gardens. Although urbanization is a negative driver of insect biodiversity, opportunities exist to implement conservation strategies in “legacy cities” that can support insects and allow us to understand how challenges of urbanization affect their distribution patterns. Legacy cities are cities that have faced significant population decline due to the fall of manufacturing industries. This has resulted in an increase in vacant land that can be revitalized to target key conservation initiatives. My research was focused on how urban habitat transformation affects predatory insects and their community assembly, distribution patterns, and diet. I used lady beetles (Coccinellidae) and long-legged flies (Dolichopodidae) as my target species due to previous evidence illustrating their decline and importance as biological control agents. My key objectives were to determine how the local management and landscape context of urban greenspaces influenced the abundance, richness, and health of these predators. To examine their health, I focused on their ability to locate prey as well as their dietary breadth. In Chapter 1, I found that habitat type had no effect on native lady beetle abundance while local variables within a site such as plant height, biomass and bloom abundance supported a greater richness of lady beetle species. Also, I found that landscape variables such as decreased impervious surface surrounding a site and sites that were surrounded by less isolated greenspace patches supported a greater abundance and richness in (open full item for complete abstract)

Committee: Mary Gardiner (Advisor); Michel Andrew (Committee Member); Megan Meuti (Committee Member); Carol Anelli (Committee Member) Subjects: Entomology

Doctor of Philosophy, University of Toledo, 2019, Biology (Ecology)

Invasive species are one of the top threats to native biodiversity. Their population genetics and genomics can be useful in control and management of invasive species and can be regarded as accidental evolutionary experiments. Here, in a temporal study of the high impact invasive round goby Neogobius melanostomus in the Laurentian Great Lakes, the ability of invasion genetics to track sources and temporal changes in population structure was demonstrated. We tested for three possible alternative temporal patterns in population genetic diversity over time – termed the `genetic stasis', `supplementation', and `replacement' hypotheses. `Genetic stasis' or no change in allelic composition over time could be caused by a large number of introduced propagules that possibly possess all (or most) of the diversity present in the native source, or by a density dependent process circumventing the establishment of later arrivals. Alternatively, there may be `genetic supplementation' in which populations that experienced an initial founder effect then gain diversity over time. Finally, `replacement' of all or some of the initial founding genetic diversity could result when the early arrivals are the best dispersers, followed by those that are better competitors. Results showed that near the site of initial establishment (the invasion core), high genetic diversity due to a large number of introduced individuals precluded significant changes in allelic composition over time. Further from the invasion core, some slight changes in genetic diversity occurred soon after population establishment. Results supported `genetic stasis' and the founder takes all hypothesis. Due to the territoriality of adult round gobies, it is possible that a density dependent process circumvented establishment of later arrivals. Additional introductions from separate native sources were implicated in some areas of the invasion. Detection of newly introduced species before they can become established and (open full item for complete abstract)

Committee: Carol Stepien (Committee Chair); Jonathan Bossenbroek (Committee Member); Kerry Naish (Committee Member); Matthew Neilson (Committee Member); Von Sigler William (Committee Member) Subjects: Bioinformatics; Biology; Ecology; Genetics; Organismal Biology

Master of Science (MS), Ohio University, 2005, Environmental Studies (Arts and Sciences)

This study documented the terrestrial vascular flora of Strouds Run State Park (SRSP) in Athens Co., Ohio, and compared it with an earlier flora of the same area completed in 1957. Differences in the species composition of the herb layer between mixed mesic and oak forest and between differently aged stands were analyzed using NMS ordination. Over the course of two growing seasons (2003 and 2004), 624 species in 106 families were found in SRSP. The number and abundance of invasive species increased since 1957, but the percentage of species that are exotic decreased. The abundance of some ant-dispersed species increased, some decreased, and some remained the same. The abundance of most medicinal herb species has changed little since 1957, with the exception of goldenseal ( Hydrastis Canadensis ), which has greatly increased. An NMS ordination of the herb-layer species composition of plots showed a clear separation between mesic and oak forest, and between young and old stands. Separation between mesic and oak forest may be due to moisture differences; however, soil moisture was not measured in this study. A significant difference (p < 0.05) in litter accumulation and the amount of canopy cover may explain the separation of old and young stands in mesic forests, but the age separation in oak forests was not explained by the results of this study.

Committee: Philip Cantino (Advisor) Subjects:

Master of Science, University of Akron, 2005, Biology

Invasive plant species have been studied for some time now but little attention has been given to their reproductive competitive abilities. I hypothesized that visitation rate to native Lythrum alatum would be increased in the presence of invasive Lythrum salicaria and that this facilitative effect would diminish with distance. I also hypothesized that seed set in L. alatum would be decreased in the presence of L. salicaria. To test these hypotheses I set up plots of L. salicaria and placed L. alatum mixed, 5m, 20m, and 50 m away from the L. salicaria. Pollinator visitation data, seed set per plant, and germination proportion per plant were recorded and analyzed. I found that visitation rate to L. alatum by large bees (Bombus and Apis) decreased significantly as a function of distance from L. salicaria and visitation rate by small bees (Ceratina, Lasioglossum, etc.) showed a trend of increasing as function of distance. Seed set showed no significant difference as a function of distance and proportion of seeds germinated in L. alatum showed a trend of increasing as a function of distance.

Committee: Randall Mitchell (Advisor) Subjects: Biology, Ecology

Master of Science, The Ohio State University, 2024, Environment and Natural Resources

Forests across the U.S. have been shaped by indigenous stewardship for centuries, and more recently by colonial land managers. Presently these forests are facing multiple stressors such as fragmentation, plant and pest invasion, and climate change. Non-native, ‘invasive' plant species pose a threat to forest ecosystems and are responsible for disrupting the structure and function of these systems, outcompeting native plant species and disrupting soil health. This study investigates (a) management effects on plant communities in an invaded eastern hardwood forest in Coshocton, OH, and (b) decomposition of litter from native and invasive species in managed and unmanaged research plots. The research site contains remnant oak-hickory forest, used in recent history for timber production followed by several decades of disuse. During this period of non-management, several invasive species became abundant throughout the site, including Celastrus orbiculatus vine and Ligustrum vulgare shrub. In addition to infiltration by invasive species, the process of mesophication is underway in some areas of the research site, altering moisture and light availability while driving the community towards a maple-beech dominated composition. In the first chapter of this research, we utilize disturbance-based management practices in invaded forests plots. Our objectives are to (i) investigate how woody plant communities shift with time from treatment and (ii) determine whether treatment effect is contingent upon the passage of time. This research contributes to our understanding of invasive plant management and exemplifies the use of goats as an alternative to fire for the purpose of driving community shifts in invaded oak forests. Research plots were established throughout the site to capture the variety of biotic and abiotic conditions. Each plot underwent one of four treatments: (a) mechanical clearing, (b) high intensity goat browsing, (c) low intensity goat browsing, (d) no tr (open full item for complete abstract)

Committee: G. Matt Davies (Advisor); Stephen Matthews (Committee Member); Horacio Lopez-Nicora (Committee Member) Subjects: Environmental Science

Master of Science, The Ohio State University, 2023, Environment and Natural Resources

Arid and semi-arid ecosystems in western Washington state (USA) are highly valuable as they contain a diverse native flora, harbor many endemic species of fauna, and provide economic benefits. However, spatial patterns and environmental factors can alter soil physical properties and influence the expansion of non-native species such as cheatgrass in turn reducing native plant species. Understanding these ecological concerns is imperative in order to determine specific areas that are urgent for restoration and conservation. To assess these critical unknowns, this research focuses on two main objectives: i) to evaluate the distribution of invasive cheatgrass in relation to environmental characteristics, landscape disturbance, restoration, and fire history; and ii) to evaluate changes in soil physical parameters, specifically soil hardness and water infiltration, as a function of soil type, historical vegetation community, and disturbance. Results from species distribution models indicated that cheatgrass is strongly influenced by the number of fires and site-specific herbicide applications. In addition, heat load index emerged as an important environmental variable in the model indicating that cheatgrass is more likely to be present in areas with high environmental stress. In relation to the second objective, the results indicated that sandy soils were more likely to have low soil hardness and faster infiltration rates. Hard soils and slow infiltration rates were evident in plots with big sagebrush, herbaceous, and live shrub microsites sites, and with current grazing. Fire frequency, however, did not emerge as significant in the models for infiltration rates or soil hardness.

Committee: Matt Davies (Advisor); Simon Power (Committee Member); Scott Demyan (Committee Member); Steve Hovick (Committee Member) Subjects: Ecology; Environmental Science; Natural Resource Management

Master of Science (MS), Wright State University, 2022, Biological Sciences

Garlic mustard is an invasive Eurasian biennial spreading in deciduous forests of North America. Garlic mustard plants in Ohio can be infected with a strain of Xanthomonas campestris, the causal agent of black rot disease in brassicas. I examined variation in susceptibility to X. campestris among garlic mustard populations, several native wild species, and agricultural crop varieties. Twenty-four garlic mustard populations were universally susceptible to X. campestris, though disease severity varied. Cardamine concatenata and Cardamine diphylla were susceptible but can phenologically escape infection in the field. Of the 14 agricultural crops tested, three cultivars (Raphanus sativus, Brassica rapa var. Rapa Hakurei, and cv - Brassica oleracea var. capitata) were susceptible to the X. campestris strain that infects garlic mustards. Nutrient availability enhanced disease susceptibility and severity, but light had a limited effect. A survey of 31 garlic mustard populations in Ohio, Kentucky, and Indiana revealed that X. campestris is established throughout a 120 km radial distance from Dayton, Ohio. The strain of X. campestris infecting garlic mustard in the Wright State University woods was identified by sequencing as X. campestris pv. incanae.

Committee: Donald Cipollini Ph.D. (Advisor); John O. Stireman III Ph.D. (Committee Member); Volker Bahn Ph.D. (Committee Member) Subjects: Biology; Botany; Ecology; Plant Biology; Plant Pathology

BA, Oberlin College, 2016, Environmental Studies

The emerald ash borer (EAB, Agrilus planipennis), is a serious threat to the survival of ash trees (Fraxinus spp.) in North America. Various control methods have been used to eradicate the EAB, but none have been sufficiently successful. The work described in this thesis is a preliminary survey of parasitic nematodes associated with EAB, with the intent of beginning to gauge their potential as biological control agents. 447 EAB adults were collected in the summer of 2015 in Connecticut and subsequently dissected to detect the level of parasitization by nematodes. Four of these beetles were found to be parasitized by nematodes. Attempts to identify collected nematodes were based on morphological examination and sequencing of 18s and 28s rRNA genes. While one of these seems unlikely to have potential as an effective biological control agent, the others are still worth pursuing in future research.

Committee: Yolanda P. Cruz (Committee Chair); Roger H. Laushman (Committee Member); John E. Petersen (Advisor) Subjects: Environmental Studies

Master of Science, University of Toledo, 2022, Biology (Ecology)

Walleye (Stizostedion vitreum) is an ecologically, economically, and recreationally important fish species in Lake Erie that fluctuates in recruitment each year. Walleye recruitment into adulthood is dependent on their growth and survival, which is directly affected by their diet during the first year of life. In the last few decades, Lake Erie has experienced several unintentional introductions of aquatic invasive species (AIS) that have likely led to environmental and food web changes, potentially impacting age-0 walleye diet and growth. To determine how the diet of age-0 walleye has changed in western Lake Erie, we compared diet composition between 2019 (new) and1994 (historical) fish during late spring, summer, and early fall. We found that during late spring (pelagic larval stage), cyclopoid copepods dominated diets in 2019, which differed from 1994 when calanoid copepods dominated diets. From summer to early fall (demersal juvenile stage), we found that large cladoceran species and benthic invertebrates made up a large portion of diets in 2019, which differed from 1994 when fish prey comprised almost all of the diets. Additionally, two of the most recent AIS, the spiny water flea (Bythotrephes longimanus) and round goby (Neogobius melanostomus), were found in 2019 diets, suggesting that age-0 walleye are adapting to the changing food web by incorporating new prey items into their diets. Our results also suggest that zooplankton and benthic invertebrates have become important prey items for age-0 walleye in Lake Erie in the later summer and fall months. Consequently, age-0 walleye by the end of their first growing season were smaller in 2019 compared to 1994 walleye. Switching to diets dominated by smaller non-fish prey during late summer and fall months could explain why walleye were smaller in 2019 and may have implications for walleye survival and recruitment into adulthood. Continued future analysis of age-0 walleye diet would provide confirmation on whethe (open full item for complete abstract)

Committee: Christine Mayer (Advisor); William Hintz (Committee Member); Mark DuFour (Committee Member); Robin DeBruyne (Committee Member) Subjects: Biology; Environmental Science; Zoology

Doctor of Philosophy, The Ohio State University, 2021, Evolution, Ecology and Organismal Biology

Humans engineer their environments by transporting species around the planet. In a new environment, most introduced species will perish, but a small proportion can become invasive, spreading widely and impacting their environments. My dissertation explores how evolutionary processes shape invasive species. I studied two mechanisms of invasive species evolution that can induce rapid evolutionary change: hybridization (mating between genetically distinct individuals) and whole genome duplication (WGD, when offspring inherit an extra set of chromosome pairs). In Chapters 1 and 2, I describe experiments with members of the model plant genus Arabidopsis differing only in genome size and status as either parent or hybrid, effectively isolating the independent effects of WGD and hybridization on traits. I grew plants together under controlled conditions and measured traits and phenotypic plasticity (the change in trait values across imposed environmental gradients). For the handful of traits and gradients in which WGD shifted plasticity values, WGD consistently increased plasticity (Chapter 1). This study provides the most controlled experimental evidence to date in support of the hypothesis that WGD increases plasticity, a hypothesis invoked to help explain how WGD has driven evolution. In contrast to WGD, I found that hybridization produced larger effects on both mean traits and plasticity (Chapter 2). This experiment is the first to fully isolate hybridization and WGD effects on plasticity. In nature, genetic and trait variation provide the raw material allowing invasive species to initially prevail in and, potentially, adapt to the introduced environment. I examined patterns of variation related to hybridization and WGD for two invasive plant systems (Chapters 3 and 4). Chapter 3 focuses on purple loosestrife (Lythrum salicaria), a well-studied species for which other authors have documented post-introduction changes in traits and genetics. A little-studied, mo (open full item for complete abstract)

Committee: Stephen Hovick (Advisor); Alison Bennett (Committee Member); Andrea Wolfe (Committee Member); Kristin Mercer (Committee Member); Amanda Simcox (Committee Member); Robert Klips (Committee Member) Subjects: Biology; Botany; Conservation; Ecology; Evolution and Development; Genetics; Horticulture; Morphology; Organismal Biology

Master of Science, The Ohio State University, 2021, Environmental Science

Eastern oak-hickory forests are threatened by multiple factors including the increasing abundance of invasive species and the process of mesophication, the transition from xeric (shade intolerant but drought tolerant) to mesic (shade tolerant but drought intolerant) species. The encroachment of forest understories by both invasive and native mesic species has altered regeneration and recruitment processes. Increasing invasive species and mesophication have created a need for further research on how biotic and abiotic filters and species functional traits influence regeneration of native trees. Research focused on understanding different controls on the regeneration and recruitment of native tree species, and the efficacy and efficiency of two invasive species control methods, was performed at The Ohio State University's Pomerene Forest Laboratory in Coshocton, Ohio. To understand processes of regeneration and recruitment, abiotic and biotic filters were used in generalized linear models to identify patterns in abundance of 19 plant functional types × size class combinations, while Non-Metric Multidimensional Scaling (NMDS) was used to describe patterns in understory species composition. Models of functional type abundances were found to have a wide range of predictive ability across the functional type × size class combinations, due to small sample sizes and other ecological conditions not examined in this research (such as land use history). The abundance of the functional types was influenced by invasive species. The invasive species' high plasticity allowed higher levels of establishment in areas rich in available resources and forced native trees to regenerate and recruit in conditions not suitable to their functional traits. Species composition was heavily influenced by invasive and native shrubs, isolating the Walnut/Oak canopy community group from the other 4 canopy community groups. After regeneration and recruitment patterns were identified, restoration ma (open full item for complete abstract)

Committee: G. Matthew Davies (Advisor); Benjamin Wenner (Advisor); Roger Williams (Committee Member); Matthew Dickinson (Committee Member) Subjects: Environmental Science; Natural Resource Management

Doctor of Philosophy (PhD), Wright State University, 2021, Environmental Sciences PhD

Attached algae are ubiquitous components of lake benthic habitats wherever sufficient light reaches submerged surfaces. Attached algae interact with heterotrophic bacteria and fungi to form complex biofilms (“periphyton”) that provide a nutritious food source for consumers and influence biogeochemical cycling by regulating redox potential at the sediment-water interface. Despite their ecological importance, there are limited data on the role of periphyton in the Laurentian Great Lakes. I quantified wave exposure and light availability in rocky nearshore habitats in Lake Erie and Lake Huron. Periphyton biomass and productivity in nearshore Lake Erie was very high while algal biomass and productivity in Lake Huron were uniformly low irrespective of depth. Regression modeling demonstrated that wave disturbance and light availability control periphyton biomass and productivity in nearshore areas of the Great Lakes. To better understand how attached algal diversity and abundance vary with depth and substrate, I measured the biomass and composition of sediment algae and periphyton growing on Dreissena across broad depth gradients in Lake Ontario and Lake Erie. Sediment and mussel shell algal biomass were greatest around 20 m and declined with depth. Algal photosynthesis on sediments and mussels declined with depth down to approximately 40 m in both lakes. I found that sediments from both lakes were dominated by benthic diatoms and settled phytoplankton. In contrast, mussel shells harbored diverse filamentous algal assemblages. I analyzed the stable isotope signatures of Dreissena tissue and biofilms collected in Lake Ontario and Lake Erie, discovering enrichment of nitrogen isotopic signatures in both organisms with depth. DNA metabarcoding data from Lake Erie revealed that Dreissena biofilms harbor greater abundances of putative nitrifying and denitrifying bacteria than surrounding sediments, suggesting that Dreissena may be hotspots for nitrogen cycling in the Great Lak (open full item for complete abstract)

Committee: Yvonne Vadeboncoeur Ph.D. (Advisor); Volker Bahn Ph.D. (Committee Member); Soren Brothers Ph.D. (Committee Member); Katie Hossler Ph.D. (Committee Member); Silvia E. Newell Ph.D. (Committee Member) Subjects: Ecology; Environmental Science; Limnology

Master of Science, The Ohio State University, 2021, Environment and Natural Resources

Background: Oak and hickory species (Quercus spp. and Carya spp.) dominance and establishment in eastern forests have been threatened due to fire suppression, shade-tolerant species encroachment, and non-native species invasion. Conservation grazing could be an economically and ecologically sustainable alternative to control non-native plants. Before introducing goat browsing in oak-hickory forests the general and browsing behavior of goats and the economic return of conservation grazing need to be assessed. Objective: The objective of this study was to understand the general behavior and browsing selection of the goats; and quantify the costs and income of conservation grazing. Methodology: Research was implemented at OSU's Pomerene Forest Laboratory (Coshocton, OH). The understory biomass was estimated using field measurement of woody plant density and size (height and diameter) via allometric equations. Conservation grazing was implemented during July and August of 2020 in 12 circular browsing plots of 20-m diameter. Mature Boer-crossed does were randomly assigned to high- (1,019 goat days ha-1) or low browsing pressure (509 goat days ha-1). General and browsing behavior were measured via direct observation through days 1 to 4 of browsing. Seven categories of behavior were recorded: Browsing, ruminating, walking, plant interaction, standing and resting, laying down and resting, and other activities. The “bite category” method was used to estimate browsing behavior and browse preferences. The browse composition and availability were characterized via hierarchical cluster analysis (browse clusters). The vegetation nutritional quality was analyzed for carbohydrates, protein, and fiber. Goats' browsing preferences were evaluated using the Jacob Selectivity Index (JSI). Two generalized linear mixed effects models were implemented to quantify the effect of browse clusters, species, and duration of browsing on JSI. The daily browse intake (DBI g-1) and goats' diet were (open full item for complete abstract)

Committee: G. Matt Davies Ph.D (Advisor); Benjamin Wenner Ph.D (Advisor); Marília Chiavegato Ph.D (Committee Member); Sayeed Mehmood Ph.D (Committee Member) Subjects: Animal Sciences; Ecology; Environmental Economics; Natural Resource Management

Master of Science, University of Toledo, 2021, Biology (Ecology)

Grass carp (Ctenopharyngodon idella, Val.) is an invasive species in the Great Lakes region that may cause ecological damage to the lake ecosystem and harm the region's economy. Grass carp spawning was documented in the Sandusky River, Ohio, in 2015 through targeted egg sampling. Continued egg sampling in the Sandusky River suggested that grass carp spawning is related to discharge and water temperature. In this thesis, I used the egg sampling data from 2014 to 2019 to develop an empirical model to understand the likely conditions related to grass carp spawning. Using a Bayesian approach, I first established the likelihood of spawning as a function of discharge and water temperature. The results suggest that spawning is most likely to occur when discharge is above 10m^3/s and water temperatures below 25℃. Using stream-specific discharge-velocity relationships, the Sandusky River model results were extrapolated to determine the risk of grass carp spawning in eight other tributaries of Lake Erie. The Grand, Maumee, and Cuyahoga rivers in Ohio have the highest risks of spawning. The model provides a mechanism for setting research and management priorities to develop management strategies to prevent the establishment of a spawning grass carp population in Lake Erie. Furthermore, the Bayesian model can be updated with data from another river to incorporate river-specific features to identify likely spawning locations.

Committee: Song Qian (Committee Chair); Christine Mayer (Committee Member); Patrick M. Kocovsky (Committee Member); Ana Rita Gouveia (Committee Member) Subjects: Biology; Ecology; Environmental Science

Doctor of Philosophy, The Ohio State University, 2021, Environment and Natural Resources

Biological invasions threaten biodiversity and ecosystem functions. Stream ecosystems and their adjacent riparian zones are connected via a complex network of direct and indirect linkages, presenting a unique setting for the study of invasion. I investigated the effects of two different riparian invaders on stream biota and stream-riparian trophic linkages: an invasive insect (hemlock woolly adelgid Adelges tsugae; hereafter HWA) and an invasive shrub (bush honeysuckles Lonicera maackii and L. tatarica). Both sets of studies used the same basic approach at >20 streams across a gradient of invasion intensity: record geomorphology and water chemistry, collect and assess in-stream biota, quantify reciprocal subsidies, and determine riparian spider density, relative reliance on aquatically-derived energy (i.e., nutritional subsidies originating from periphyton), and invertebrate food-chain length (using naturally-abundant stable isotopes) at each study reach. I also conducted a before-after, control-impact (BACI design) honeysuckle removal experiment. My results suggest that in-stream physical and chemical alterations (i.e., large-wood characteristics and nutrient concentrations) associated with HWA invasion and subsequent hemlock decline drove changes in stream invertebrate diversity and trophic relationships. Evidence for ecological consequences of this invader was strongest at lower trophic levels. For example, periphyton biomass was greater at uninvaded reference sites than at severely invaded sites (x = 1.37 vs 0.52 mg cm-2), while relative abundance of herbivorous macroinvertebrates increased from 4 to 23% at the severely invaded sites. Spider (family Tetragnathidae) densities were 3.2 times higher at sites with severe hemlock decline and although density was not linked to emergent insect density overall, δ15N signatures of Araneidae and Pisauridae spider families tracked emergent insect δ15N (r2 = 0.42 and 0.78, respectively), suggesting a trophic linkage. (open full item for complete abstract)

Committee: S. Mazeika Sullivan (Advisor); Lauren Pintor (Committee Member); P. Charles Goebel (Committee Member) Subjects: Ecology; Environmental Science; Freshwater Ecology

Master of Science (MS), Ohio University, 2020, Environmental Studies (Voinovich)

This study investigated pollinator use across areas of the channelized Hocking River's banks in different stages of ecological succession, according to when each area last experienced a mowing disturbance. These successional stages of growth—an associated pollinator use—were compared according to each area's community structure using metrics such as diversity, leaf area index (LAI), greatest height, percentage of native plants, and percentage of noxious plants. Each successional stage was monitored over time to assess seasonal change in both vegetative growth and pollinator use. Each area was also evaluated for both actual and hypothetical roughness scenarios to determine what impact mowing regimes—and lack thereof—might have on flood potential. Considerations were given to past studies that examined community perceptions of the channelized river, as well as precipitation and flood trends. Ultimately, this study investigated whether alternative mowing practices could be socially, economically, and ecologically beneficial, without jeopardizing flood protection. The study concluded that the ecosystem service benefits of actively managed growth outweigh the risk of flooding in the channel. It recommends that further studies, including a review from the Army Corps of Engineers, be undertaken to begin the process of restoring the channelized Hocking River's riparian zone to a more sustainable and ecologically beneficial state.

Committee: Natalie Kruse Daniels Ph.D. (Advisor); Rebecca Snell Ph.D. (Committee Member); Amy Lynch Ph.D. (Committee Member) Subjects: Biology; Botany; Civil Engineering; Conservation; Ecology; Engineering; Entomology; Environmental Management; Environmental Science; Environmental Studies; Geography; History; Horticulture; Hydrologic Sciences; Hydrology; Landscape Architecture; Management; Plant Biology; Plant Sciences; Pollen; Wildlife Conservation; Wildlife Management