UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
14 results
Search Results
Item LEVERAGING FINE-SCALE GEOSPATIAL DATA TO ADVANCE BIODIVERSITY SENSITIVE URBAN PLANNING, WILDLIFE MANAGEMENT, AND GREEN CORRIDOR DESIGN: APPLICATION TO THE DISTRICT OF COLUMBIA(2023) Spivy, Annette Leah; Mullinax, Jennifer; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Typically, urban wildlife communities are made up of generalist species that are adept at utilizing human resources. However, many wildlife species struggle in the face of extensive urbanization and would benefit from increased conservation of urban green space, increased urban landscape connectivity, and proactive wildlife population management strategies. Unfortunately, maintaining and/or increasing the availability of quality habitat for biodiversity conservation in urban areas can be challenging as these conservation efforts are often influenced by the decreasing availability of critical resources and the challenges in allocating those resources among competing socioeconomic and environmental needs. Therefore, to improve the management and conservation of urban wildlife, accurate measurements of potential trade-offs between the environmental, economic, and social goals and management actions of a city’s sustainable development plan are needed. Until now, much of the effort in wildlife habitat modeling and biodiversity mapping has been across large geographic areas or broad spatial scales. Those efforts have provided valuable insights into overall biodiversity patterns, identifying key hotspots, and understanding large-scale ecological processes. However, in urban environments, the dynamics of wildlife, habitat availability, and ecosystem services operate differently than in natural or rural landscapes. As urbanization continues to expand, there is a growing need to focus on fine-scale factors to address specific conservation challenges in urban systems. This research seeks to address some of these challenges and demonstrates how new and traditional species-relevant geospatial datasets can be leveraged in urban planning and design to drive local-scale conservation decisions that put biodiversity in the forefront. This work links long-term, multi-taxon, wildlife survey data and high-resolution land use and land cover datasets (1m) to determine where high-quality, well-connected habitats exist, or could most easily be justified and acquired, within the District of Columbia. This work also evaluates the spatial patterns of ecosystem service provisions across the urban landscape to identify “win-win” areas for conservation or restoration that will benefit both biodiversity and human wellbeing. Finally, the work evaluates a local translocation effort of the vulnerable eastern box turtle (Terrapene carolina carolina) to inform mitigation strategies when a sudden loss of habitat in an urban environment is inevitable. This research is particularly relevant to wildlife managers and urban planners in highly urbanized areas, where large parcels of land with suitable habitat are minimal and municipal environmental departments are often under-resourced. Local policymakers interested in incentivizing conservation efforts to meet state or national goals can use this information for strategic urban conservation initiatives.Item MANAGEMENT OPTIONS FOR FARMERS FACING SALTWATER INTRUSION ON THE EASTERN SHORE OF THE CHESAPEAKE BAY(2023) Schulenburg, Alison Nicole; Tully, Kate; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rising sea levels, storms, and perigean spring tides push saltwater into coastal agricultural fields. This phenomenon, known as saltwater intrusion, alters nutrient cycling and damages crop yields. As sea levels continue to rise, saltwater intrusion will only worsen, with devastating consequences to agroecosystems along the coast of the Chesapeake Bay. Researchers and farmers alike are looking for solutions to adapt to and mitigate the effects of saltwater intrusion. Landowners may respond by altering their management practices. Farmers may 1) adapt by planting a salt-tolerant crop, 2) attempt to remediate soils with trap crops, 3) restore native marsh grasses, or 4) abandon fields altogether. My project investigates the survival of different crops and plant treatments under saltwater-intruded conditions and the potential for these plants to survive and to remove excess nutrients (e.g. sodium and phosphorus) from the soil, with the overall goal to benefit both the farming community and water quality in the Chesapeake Bay. Results from this study will help inform new management practices to increase soil health and maintain crop yields. Finally, the goal of this work is to guide local best management practices and potential easement opportunities for landowners facing saltwater intrusion, and ultimately determine optimal strategies for climate resilience.Item Turion size advantage in the restoration of Vallisneria americana: the importance of genetic identity and diversity(2019) Carew, Anne; Engelhardt, Katia; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The restoration and rehabilitation of damaged ecosystems has become a worldwide endeavor utilizing vast resources and ecological knowledge to build functioning and resilient ecosystems. Biodiversity restoration increases the likelihood that present species are well-adapted to the environment or can complement each other in resource use. Genetic diversity in populations may increase establishment rate, resistance to invasion, and resilience in a changing world. In parallel field and greenhouse experiments, I established colonies of the submersed aquatic macrophyte Vallisneria americana. Colony survival and performance was affected by environmental conditions in the field and genotypic diversity in the greenhouse. In the presence of nonnative Hydrilla verticillata, V. americana height was reduced; however, biomass increased, suggesting resource partitioning in response to competition. These results suggest that genotypic identity and diversity are important in early establishment of plant populations and calls attention to designing restorations that incorporate genetic information about source populations.Item HYDROLOGICAL, BIOLOGICAL, AND GEOCHEMICAL RELATIONSHIPS AMONG CARBON, NITROGEN, AND BASE CATIONS IN RESTORED AND UNRESTORED URBAN STREAMS(2017) Doody, Thomas Rossiter; Kaushal, Sujay S; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urban infrastructure changes hydrologic flowpaths of water into streams and alters ecosystem function. Geomorphic stream restoration is commonly implemented to stabilize channels, while ecosystem function, and nutrient retention are of secondary concern. This research investigated whether restoration alone significantly influences N uptake in streams and if significant hydrological, biological, and geochemical relationships exist between coupled biogeochemical cycles that should be considered when evaluating restorations. Carbon, nitrogen, base cations, and stream metabolism dynamics were investigated in six urban streams in Baltimore,MD. Nitrate tracer injections were used to quantify nitrogen uptake dynamics. Results did not show significant differences in nitrogen uptake based on restoration. Organic carbon, inorganic carbon, and nitrogen each have distinct but interrelated hydrological, biological, and geochemical relationships across all sites. These dynamic relationships may also significantly affect nitrogen uptake, but more spatiotemporal data are needed to quantify and understand variability among restored and unrestored sites.Item RESPONSE OF PLANKTON COMMUNITIES IN COASTAL LAGOONS TO CHANGES IN NUTRIENT QUALITY AND QUANTITY: CASE STUDY OF FLORIDA BAY(2016) Shangguan, Yini; Glibert, Patricia M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Comprehensive Everglades Restoration Plan was initiated to return Florida Bay to a more natural ecological state. The C-111 project, one phase of this plan and initiated in 2012, was designed to increase freshwater flow into northern Florida Bay. However, it also alters the nutrient regime and, potentially, phytoplankton biomass and assemblage. This dissertation investigated the combined effects of changes in discharge and nutrient on phytoplankton biomass and assemblage in several interconnected, mesohaline coastal lagoon systems (lakes) of Florida Bay using field observations, mesocosm experiments, and a statistical box model. Field measurements on nutrients and phytoplankton were performed before and after C-111 implementation. After C-111, increased freshwater flow and phosphorus (P) input, but decreased salinity and nitrogen (N) input were observed. One set of the lagoon lakes, previously highly eutrophic (average chlorophyll a >20 ug L-1), had a nearly 50% decline in overall phytoplankton biomass. The other set of lakes, originally oligotrophic (average chlorophyll a <2 ug L-1), had a doubling of phytoplankton biomass. Phytoplankton assemblage in both sets of lakes shifted to picocyanobacteria. Mesocosm experiments (5 independent experiments, 5-10 day duration, 1000 L tanks) were conducted to test the effects of nutrient additions. Phytoplankton biomass increased 3 to 10-fold in the +P treatments (alone or +N), but did not increase substantially in the +N alone treatments. The +N+P treatments, particularly the +NO3-+P at a +N:P molar ratio of 32 led to a 20-fold increase in diatoms, whereas N in the form of +NH4+ yielded a > 2-fold increase in picocyanobacteria. A statistical box model based on relationships measured in the field under different salinity regimes was developed to simulate flow, nutrients, and phytoplankton changes in the eutrophic lake chain. Model output showed that higher freshwater discharge decreased phytoplankton biomass in the upper of the connected lakes, but the lower lake had a high potential to generate algal blooms, which is consistent with the field data. Also, picocyanobacteria tripled following an increase in dissolved organic nitrogen (DON). This study recommends co-management of both P and N, particularly NH4+ and DON in Florida Bay if picocyanobacteria blooms are to be controlled.Item Ecosystem dynamics in tidal marshes constructed with fine grained, nutrient rich dredged material(2015) Staver, Lorie Winchell; Stevenson, J. Court; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An ecological study was undertaken of the tidal marshes at Poplar Island, a restoration project utilizing fine grained dredged material from the shipping channels in upper Chesapeake Bay. The goals of the study were to examine the effect of a nutrient rich substrate on vegetation development, elevation change, and nutrient cycling in the constructed tidal marshes. Specifically, I examined macrophyte production, nitrogen (N), carbon (C) and silicon (Si) budgets, as well as the success of a silica amendment in enriching plant tissue concentrations. Establishment of Spartina alterniflora and S. patens on fine grained dredged material was rapid, and growth peaked in the second year. Thereafter S. alterniflora dieback occurred sporadically during the growing season, but the causes remain unclear. Elevation change averaged 7.9 ±0.8 mm y-1 in the dredged material marshes (low marsh only), compared to 7.4 ±1.4 mm y-1 in a low nutrient onsite reference marsh. Elevation change was significantly correlated with biomass production suggesting that inputs of organic matter from high rates of aboveground biomass production on nutrient rich dredged material offset the reduced contribution of belowground biomass to vertical accretion. However, dieback may have a detrimental effect on vertical accretion, which is essential for keeping up with apparent sea level rise (13.6 and 11.0 mm y-1 at Baltimore and Solomon’s tide gauges, respectively) since elevation monitoring began at Poplar Island. The tidal flux study revealed that the marsh exports ~665 kg of N y-1, including 100 kg NH4+-N y-1, and 67,874 kg y-1 TSS, and imports 35 kg NO3-N y-1. Silicon is also exported on both a seasonal and annual basis, including 4,337 kg dissolved Si y-1 and 3,924 kg biogenic Si y-1, with highest exports in July, an overlooked benefit of dredged material restoration projects. Soil Si amendments increased plant tissue concentrations significantly, but this study did not show increased resistance to N related stress effects on the vegetation. Overall, this study suggests that when considering trajectories of vegetation development, nutrient exchanges and elevation change in constructed marshes, it is essential to consider the initial nitrogen content of the substrate.Item THE EXCHANGE OF EASTERN OYSTER (CRASSOSTREA VIRGINICA) LARVAE BETWEEN SUBPOPULATIONS IN THE CHOPTANK AND LITTLE CHOPTANK RIVERS: MODEL SIMULATIONS, THE INFLUENCE OF SALINITY, AND IMPLICATIONS FOR RESTORATION(2015) Spires, Jason Eugene; North, Elizabeth; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With limited funds available for restoration and management, information is needed that would enhance the objectives of restoration of the eastern oyster (Crassostrea virginica) in Chesapeake Bay. One challenge with choosing locations for C. virginica restoration is lack of information regarding larval exchange, which helps determine whether the reefs will be self-sustaining and/or enhance nearby populations. The goal of this research was to estimate the larval exchange between subpopulations within the Choptank and Little Choptank Rivers (Maryland, USA) and to determine the influence of low salinity on these patterns in connectivity. To this end, the Lagrangian TRANSport model (LTRANS) was coupled with a Regional Ocean Modeling System hydrodynamic model of Choptank River (ChopROMS) and applied to predict the exchange of simulated C. virginica larvae between 596 reefs within the system. Model results indicated that there is a high degree of connectivity among the subpopulations in this system. Most simulated larvae were transported down river (rather than upriver). Reefs in upper portions of the Choptank River and its tributaries were in a position to produce the most larvae which encountered suitable habitat, whereas those in the lower Choptank River received the most simulated larvae. In addition, salinity-induced mortality of larvae substantially decreased transport success and self-recruitment, and changed patterns in reef-specific transport success throughout the estuary. Model results provide region-specific information that could be used to support restoration efforts in areas with low salinities like the Choptank River.Item Assessing Wetland Restoration on the Delmarva Peninsula using Vegetation Characteristics(2015) McFarland, Eliza Katherine; Baldwin, Andrew H; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With wetland restoration, post-restoration monitoring is essential for determining developmental trajectories, particularly when comparing to natural reference systems. As part of the Mid-Atlantic Conservation Effects Assessment Project, 15 depressional wetlands on the Delmarva Peninsula of Maryland and Delaware were surveyed for above-ground vegetation and seed bank community composition, annual biomass production, and vegetation carbon content (10 restorations from prior-converted cropland (aged 5-31 years), and 5 natural forested depressions). Within each wetland, hydrologic zones (emergent, transition, upland) were also denoted and sampled. Restored wetlands showed more seed bank community similarity to natural wetlands than above-ground vegetation communities. Restorations also produced more annual herbaceous biomass than natural systems, and lower annual leaf litter biomass. After this period of post-restoration development, restored wetlands do not perform vegetation-related functions identical to their natural counterparts; however, these restorations are performing important vegetation-based functions that require yet more time to truly develop.Item Enhancing Vallisneria americana restoration using knowledge of genotypic and phenotypic diversity(2015) Marsden, Brittany West; Neel, Maile C; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vallisneria americana Michx. (Hydrocharitaceae) is an ecologically important submersed aquatic plant that once dominated freshwater to oligohaline environments in eastern North America. After dramatic declines it is the target of many restoration initiatives. To increase knowledge of the capacity of remaining populations to either adapt through natural selection or acclimate to emerging environmental conditions, I combined genetic data and common environment experiments to quantify V. americana genetic diversity and differentiation at local to regional scales, evaluate evidence of local adaptation to different climate conditions, and assess evidence of inbreeding or outbreeding depression. I quantified the structure of genetic diversity in five sites from the tidal Potomac, Hudson, and Kennebec Rivers, and 33 sites across the species' distribution in the Potomac. Genotypic (0.1-1.0) and allelic diversity (1.5-5.5), observed heterozygosity (0.34-0.72), and relatedness (-0.06-1.00) varied greatly along rivers and across latitude. Hudson V. americana had the lowest genetic diversity and Potomac had the highest. Differentiation and network analysis of relatedness revealed no common genetic diversity distribution patterns within rivers. Major differences in genetic structure were observed across the tidal and non-tidal Potomac. Common environment experiments evaluating growth and reproductive performance of Potomac, Hudson, and Kennebec V. americana grown in different temperature and photoperiod conditions only found evidence of local adaption in Potomac plants. Few overall differences in morphological and life history traits were observed between local and foreign plants. Plants grown under global warming conditions had reduced performance. Limited evidence of local adaptation and high acclimation to different conditions suggest that populations have high potential for resilience in the face of climate change, so long as temperatures do not exceed thermal tolerances. Climate change mitigation strategies that involve transplanting individuals may also be successful. To investigate consequences of restoration strategies that translocate individuals, I evaluated seed production and germination success of controlled reproductive crosses between V. americana within and among genetically differentiated populations in the Chesapeake Bay. There were no consistent patterns of inbreeding or outbreeding depression in crosses. Effects of mixing sources were site-specific and not predicted by levels of relatedness among individuals, genetic diversity within, or differentiation among populations.Item Carbon Storage and Potential Carbon Sequestration in Depressional Wetlands of the Mid-Atlantic Region(2011) Fenstermacher, Daniel E.; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With recent concern over climate change, methods for decreasing atmospheric levels of greenhouse gasses such as CO2 have been of particular interest, including carbon sequestration in soils that have depreciated levels of carbon from cultivated agricultural crop production. The Delmarva Peninsula contains many Delmarva Bay landforms, which commonly contain wetlands. Five pairs of Delmarva Bays were selected to examine change in carbon stocks following conversion to agriculture and to assess the potential for carbon sequestration if these soils were to be restored hydrologically and vegetatively. A loss of approximately 50 % of the stored soil carbon was observed following the conversion to agriculture. If these agricultural soils were to be restored, the wetland soils within the Delmarva Bay basin are predicted to sequester a total of approximately 11 kg C m-2 and the upland soils of the rim would be expected to sequester a total of approximately 4 kg C m-2.