Doctor of Philosophy, The Ohio State University, 2022, Environmental Science

Tropical savannas support globally important biological diversity and provide a variety of cultural and economic ecosystem-services to humans. As mosaic landscapes, they are characterized by the coexistence of woody and grassy habitats which are strongly regulated by abiotic gradients (e.g., soils, climate) and local disturbance regimes (e.g., fire, flooding and grazing). Consequentially, savannas are inherently dynamic over a variety of scales and provide an array of temporal and spatial ecological niches for wildlife. However, tropical savannas and their ecological functions have been widely degraded by intensifying human land-use and are threatened by impending climate change. Unfortunately, our scientific understanding of savanna ecology is currently limited, impeding development of appropriate conservation approaches. This is especially true of Neotropical systems. This dissertation provides new research, carried out within the Beni, a seasonally flooded Neotropical savanna in Bolivia, that aims to address critical knowledge gaps in savanna ecology. This research will contribute to developing sustainable land management and restoration initiatives to secure and protect savanna ecosystems for people and wildlife. The overarching aim was to understand how ecological (flooding) and agricultural (managed fire and cattle grazing) disturbance influences habitats and wildlife in Beni. To achieve this, three specific objectives were identified: 1) understand how restoration, through cessation of long-term cattle grazing impacts (i) regeneration, (ii) understory structure and composition, and (iii) abundance and diversity of large mammals and nocturnal birds, within the regions' naturally patchy gallery forests; 2) examine how compounded disturbance from flooding and fire shapes the distribution of woody plants and habitats across a savanna-grassland mosaic; and 3) determine functional responses of avian biodiversity to livestock removal across a savanna-grassland ec (open full item for complete abstract)

Committee: G. Matt Davies (Advisor); Christopher Tonra (Advisor); Stephen Matthews (Committee Member); Kaiguang Zhao (Committee Member) Subjects: Conservation; Ecology; Environmental Science; Range Management; Wildlife Conservation

Ph.D., Antioch University, 2021, Antioch New England: Environmental Studies

Seagrass meadows and mangrove forests are ecologically and economically important systems that are increasingly threatened by anthropogenic activity. This study used a non-invasive method, baited remote underwater video systems (BRUVS), to observe mobile marine vertebrates in the seagrass-mangrove ecotone in North and South Bimini, the only area where mangroves remain in the northwestern Bahamas. An extensive area of mangroves and seagrass was removed for coastal development in North Bimini, where a marine protected area, the North Bimini Marine Reserve (NBMR), has been under consideration for decades. This research applied principles of seascape ecology to assess species abundance, diversity, and richness of marine fauna at 102 BRUVS deployment sites to answer the central research question, how does seascape composition and configuration influence mobile marine vertebrates in seagrass meadows adjacent to mangrove and non-mangrove habitats in Bimini, Bahamas? Findings highlighted the importance of the seagrass-mangrove ecotone for marine vertebrates (teleosts, elasmobranchs, and reptiles) with greater species abundance, diversity, and richness associated with denser seagrass near mangrove-lined shores.

Committee: Lisabeth Willey PhD (Committee Chair); James Jordan PhD (Committee Member); Phil Colarusso PhD (Committee Member) Subjects: Ecology; Environmental Studies

Master of Science (MS), Wright State University, 2019, Biological Sciences

In this study, I examined how the spatiotemporal distribution of spider webs and diet changed in a lake riparian zone with increasing distance from an aquatic resource. I surveyed twenty, one-hundred meter transects along the perimeters of Sanford and Escanaba lakes (Wisconsin). Overall, spider web abundance was highest near the lakes and decreased moving into the adjacent forest. Horizontal orb webs, vertical orb webs, and mesh webs showed strong negative relationships with distance from the lakes. Aquatic insects composed an average 36-64% of spider diet for all spider families throughout the riparian zone, suggesting that some spider families are selecting habitats where aquatic prey availability is high. However, all are passively capturing aquatic prey as an abundant resource. These results demonstrate the value of riparian habitats to terrestrial communities and show that spiders could provide a model for assessing the reciprocal flow of allochthonous inputs between aquatic and terrestrial communities.

Committee: Thomas Rooney Ph.D. (Advisor); Katie Hossler Ph.D. (Committee Member); John Stireman III Ph.D. (Committee Member) Subjects: Ecology

Doctor of Philosophy, Miami University, 2004, Zoology

Stream ecosystems are holistic systems that incorporate disturbances and abiotic influences at many spatial and temporal scales. This view supports a three-tiered model of variables that determine biotic integrity in streams, with causes and effects flowing from large-scale to fine-scale processes. Tier One characteristics include variables important at the scale of geomorphological processes and land use over entire watersheds. These variables largely determine Tier Two factors, abiotic conditions in a stream reach. Tier Two variables, in turn, largely structure the Tier Three variables, the stream's biotic communities. Through field studies and GIS analysis, relationships among these three tiers of variables were examined in this research to explore the question of how agriculture exerts its influence on stream fishes. This study investigated 27 streams, in two ecoregions and the transition area, or ecotone, between them, in south-central Ohio. The study design allowed questions to be asked concerning the relative influence of geomorphology and land use in varied landscapes, as well as relative impacts of watershed versus riparian land use. The region also contained relatively equal proportions of three types of agriculture (hay, row crops, and pasture) allowing the study to address the question of which land use might be most harmful to stream fish. This study supported the importance of row crop agriculture, finding it to be the most degrading type of agriculture for stream fish, but also found pasture to be an important causal factor in stream community degradation. This study also supported the importance of riparian buffers, finding riparian agriculture to be more degrading than agriculture over the entire watershed. A more interesting finding is the suggestion that a minor amount of nutrient enrichment from agricultural land use may benefit streams that are naturally oligotrophic. A possible mechanism could be increased primary production, which increases ma (open full item for complete abstract)

Committee: Orie Loucks (Advisor) Subjects: Biology, Ecology