Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

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

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    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).
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    Vegetation-Hydrodynamic Interactions and the Stability of Channel Inlets of Tidal Freshwater Wetlands, Chesapeake Bay System
    (2014) Statkiewicz, Anna; Prestegaard, Karen L; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    To maintain elevation, deposition of mineral and organic sediment in tidal freshwater wetlands (TFWs) must outweigh losses due to sea-level rise, erosion, decomposition, and compaction. Sediment loads into tidal marshes are controlled by inlet size and sediment supply, but interactions among vegetation, hydraulics, and geomorphology affect sediment retention. This study focused on these interactions in TFW inlets partially covered by aquatic vegetation (N.luteum, Z.aquatica, and H.verticullata). Measurements of hydraulic parameters and geomorphic change were correlated with observations of spatial and morphological characteristics for each vegetation type. The aquatic plants grew in significantly different water depths and well-defined platforms formed in areas occupied by emergent vegetation where effective shear stress is lowest. Net annual accretion data indicate an inverse relationship between maximum inlet depth and accretion rate. These results suggest that initial vegetation colonization modifies channel inlet morphology; both vegetation and morphology generate the shear stress distributions, which maintain channel form.