Theses and Dissertations from UMD
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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 give thesis/dissertation in DRUM
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Item MEGAPOOLS: VEGETATION DIEBACK AND RESTORATION POTENTIAL OF A DITCHED COASTAL SALT MARSH(2023) Stahl, Katherine A.; Baldwin, Andrew H; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In many ditched coastal salt marshes, megapools, or large ponded areas of vegetation dieback,have formed. In combination with sea level rise, this interior marsh loss can decrease wildlife habitat suitability, resilience to storms, and other ecosystem services. However, mechanisms of megapool formation are poorly understood, hampering restoration efforts. Here, we explored differences in environmental characteristics between megapools in different stages of formation (Fully Formed, Partially Formed and Nonformed/Control) and between Elevations within megapools (High, Medium, Low). Using IRIS Films (Indicator of Reduction in Soil), we found that Fully Formed megapools had higher sulfide concentrations than Partially formed, which in turn were greater than Nonformed megapools. We additionally found that lower elevations correlated with higher sulfides, lower plant coverage, lower belowground biomass, lower Carbon Density, and predicted megapool type. We noted that in terms of elevation, vegetative cover, and biomass, Nonformed and Partially formed were more similar as were High and Medium elevations. Whereas in terms of soil characteristics, Fully Formed and Partially formed were more similar as were Medium and Low Elevations. To combat megapools and dieback, we will assess the effectiveness of two restoration techniques, the first of which is assessing the survival and growth of plantings at different spacings, elevations, and megapool formation levels. We found survival and growth was higher in Partially formed megapools than Fully formed, and no impact by spacing or elevation. Our second restoration technique is runnels, or 15” channels that reconnect megapools to ditches, which were installed in January of 2023. The data collected above will act as baseline data, repeated again. These baseline results support a close relationship between pool stages of formation, carbon storage, elevation, vegetation health, biomass production, and sulfide levels (Graphical Abstract).Item Embodied Performance: War, Trauma, and Disability on the Eighteenth-Century Stage(2021) LeRoy, Tamar Dora; Rosenthal, Laura; English Language and Literature; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This project brings attention to the emotional work performed by plays about war from the Restoration and eighteenth century—how these plays position soldiers and communities in relation to one another and the state and in what ways they contribute to the work of negotiating trauma. War-themed plays of the period obsessively reenact tropes and devices that communicate particular affective scenarios or experiences of wartime. These affective scenarios include the temporality of soldiering and enlistment that locks the recruit in a state of inevitable injury and injuring; the longings for return of someone seemingly lost or displaced and the simultaneous fear of the outcome of this return (or no return); and a sense of rootlessness or displacement that unsettles surety in homeland, homecoming, or nation. The tropes and devices that convey these affective scenarios include devices involving the literal substitution bodies, such as bed tricks and dead tricks; an obsessive repetition of scenarios of recognition of identity, reunion, and the many complications of mistaken identity; and humor, joking, and comic tropes (like the soldier breeches role) that communicate a sense of the corporeal/temporal experience of war through the body. From these devices an experiential bridge is created in the playhouse between home front and warfront that positions the soldier as well as the grieving individual as part of a larger affective community. These figures are not isolated by their potentially extreme experiences of the battlefield, enlistment, waiting, or mourning: through the collective space of the stage, their extreme experiences are shown to be acknowledged by the larger group. From these plays, we see the affective experience of war at home from the community networks touched by military conflict.Item TREE TRADE-OFFS IN STREAM RESTORATION: IMPACTS ON RIPARIAN GROUNDWATER QUALITY(2020) Wood, Kelsey Lynn; Kaushal, Sujay; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Restoring urban degraded stream channels in efforts to improve water quality often includes substantial alteration of the riparian zone which can require the removal of mature trees. This study assessed the impact of tree removal on riparian groundwater quality over time and space using a chronosequence of restored sites ages 5-20 years and well transects along groundwater flow paths. The response of multiple elements through various hydrologic conditions was evaluated by monitoring dissolved concentrations of inorganic carbon, organic carbon, total nitrogen, boron, calcium, copper, iron, potassium, magnesium, manganese, sodium, and sulfur over a 2-year period. Results revealed that concentrations of most bioreactive and organically derived elements were significantly elevated and increase along flowpaths at recently restored sites.Item Salinity and Inundation Tolerance of Phragmites australis ssp. americanus: A Greenhouse Experiment and Field Study on a Tributary of the Chesapeake Bay(2017) Leason, Diane Elizabeth; Baldwin, Andrew H; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Natural vegetation communities of tidal and non-tidal wetlands are threatened by invasive species, e.g. Phragmites australis (Cav.) Trin. Ex Steud., resulting in diversity losses and declines in wetland services. The native lineage of Phragmites, Phragmites australis ssp. americanus Saltonstall, P. M. & Soreng could be a valuable addition to species currently used in restoration projects aimed at increasing wetland services. However, tolerances of native Phragmites to environmental conditions are uncertain. Salinity and water level tolerances were investigated by monitoring growth of adult plants, established from rhizomes, under varying water and salinity levels in a greenhouse experiment and an observational study. Results show salinity levels above 5 ppt significantly limited growth of native Phragmites regardless of water level indicating appropriate restoration use across the marsh platform of fresh and oligohaline systems. Educational materials and demonstration sites were created to improve field identification of native Phragmites.Item Healing Invisible Wounds: Landscapes for Wounded Warriors Suffering from Posttraumatic Stress Disorder (PTSD)(2013) Ashmun, Sarah C.; Sullivan, Jack; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Characterized by pervasive symptoms of intrusion, numbing, and hyperarousal, coping with PTSD can be a tenacious and lifelong challenge for sufferers (Cahill and Foa 2010). Given the recent surge of war veterans resulting from Operations Enduring and Iraqi Freedom with a high prevalence of PTSD, landscapes may provide a free and accessible means for veterans to successfully cope with their PTSD symptoms and seek treatment. The intention of this project is to merge holistic therapies for PTSD with successful landscapes for trauma patients into the creation of adaptable design principles. Guiding Principles for PTSD will be incorporated into the design of a Healing Woodland for wounded warriors at the Walter Reed National Military Medical Center in Bethesda, Maryland, while also providing potential solutions for other sites aiming to incorporate holistic therapies for PTSD into the landscape.Item Water Flow and Sediment Texture as Co-Varying Submersed Aquatic Vegetation (SAV) Habitat Requirements(2013) Swerida, Rebecca M.; Koch, Evamaria W; Sanford, Lawrence P; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study examined the importance of water flow and sediment texture as co-varying habitat parameters of submerged aquatic vegetation (SAV) in the Chesapeake Bay. An outdoor mesocosm experiment was conducted to test the response of SAV (Zostera marina and Ruppia maritima) to combinations of water flows and sediment grain sizes characterized by sediment deposition, bedload transport and erosion. Water flow, sediment and SAV characteristics were also determined at vegetated and adjacent unvegetated areas at 11 study sites and sediment motion conditions assessed. Greater SAV biomass was developed by Z. marina and R. maritima experiencing sediment motion than sediment deposition. Although habitat parameter thresholds in situ were site-specific, overall SAV presence was limited to moderate ranges of both water flow and sediment grain size. All SAV habitat observed was characterized by sediment bedload transport. Consideration of both water flow and sediment habitat requirements will improve SAV restoration success.Item VEGETATION PATTERNS IN DEPRESSIONAL RESTORED, NATURAL REFERENCE, AND PRIOR-CONVERTED WETLANDS IN THE USA MID-ATLANTIC COASTAL PLAIN.(2012) Yepsen, Metthea; Baldwin, Andrew; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vegetation responds quickly to environmental changes, making it a useful tool for assessing the success of wetland restorations. Plant community composition was compared in 47 sites across the coastal plain of Maryland, Delaware, Virginia, and North Carolina, USA. Fifteen of the sites were isolated depressional wetlands (natural reference), 16 were farmed "prior-converted cropland" sites (ditched and drained former wetlands), and 17 were restored wetlands. Prior-converted sites were highly disturbed and dominated by non-wetland conventional row crops. Natural reference sites were dominated by native woody species and restored sites were dominated by herbaceous wetland species. Natural reference sites had lower Anthropogenic Activity Index scores, higher average coefficients of conservatism, and higher Floristic Quality Assessment Index scores than restored and prior-converted sites. Wetland restorations have succeeded in developing wetland plant communities, but have not developed plant communities that match natural reference wetlands. This is likely due to continued human disturbance, age, and a lack of proper propagules.