The Great Dismal Swamp (GDS) is a forested peatland located in the Atlantic Coastal Plain. Once a mosaic of wetland communities, disturbances (e.g., timber harvesting and ditching) have resulted in altered hydrologic regime, homogenized forest communities, and increased peat subsidence. In response, hydrologic restoration and forest management aim to enhance community composition and function. To help inform these efforts, we investigated variability and drivers of forest communities by surveying vegetation composition and structure, hydrologic indicators, and soil properties at 79 monitoring plots across GDS. Data were augmented with modeled water levels and peat depths. Our results demonstrate red maple (Acer rubrum) dominance across GDS, which decreases tree density, richness, and diversity. However, hierarchical cluster analysis identified four community types: Gum (G), Maple-Gum (M-G), Sweetgum-Maple (SG-M), and Maple (M). These communities differed in tree composition and structure; differences in other growth forms (shrubs, herbaceous, and regeneration) were limited. Modeled water levels failed to explain vegetation differences, but community associations with soil properties suggest that communities exist along a hydrologic gradient. Specifically, the G community likely exists on wetter sites whereas SG-M communities occur at drier locations. Maple-dominated communities (M and M-G; 78% of plots) likely occur across broader hydrologic gradients, explaining their dominance. However, more characterization of hydrology (i.e., time-varying water levels and soil moisture) and other drivers (e.g., site history and soil hydraulics) is needed to further explain community variation. As such, we propose future strategies for long-term monitoring to inform ongoing hydrologic restoration and forest management efforts. / Master of Science / The Great Dismal Swamp (GDS) is a large forested wetland located in southeastern Virginia and northeastern North Carolina. The GDS provides many ecosystem services such as wildlife habitat, biodiversity, water quality and storage, and carbon storage. Prior to disturbance, the GDS was composed of a variety of forest types, including stands dominated by cypress (Taxodium spp.), cedar (Chamaecyparis spp.), and pocosin (Pinus spp.) species. However, land use activities (e.g., ditching, draining, and timber harvesting) have resulted in drier conditions, forests dominated by red maple (Acer rubrum), land subsidence, and increased fire frequency. To restore the GDS to its pre-disturbance state, water control structures have been installed in drainage ditches to increase wetland water levels throughout the swamp. To inform those efforts, research is needed to understand how forest communities will respond to changing hydrology. In this study, we investigated forest composition throughout the GDS and found that four forested communities exist: Gum (G), Maple-Gum (M-G), Sweetgum-Maple (SG-M), and Maple (M). Our findings demonstrate that the M community is the most abundant community at GDS. Where red maple is present in large quantities, the variety of other tree species decreases. Additionally, we found that these communities exist on different degrees of wetness. The G community is located on wet sites, and the SG-M is located on dry sites. The more mapledominated communities (M and M-G) are found across a larger range of wetness conditions. Our findings will inform future monitoring and management efforts at GDS.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/84343 |
| Date | 20 July 2018 |
| Creators | Ludwig, Raymond Francis |
| Contributors | Forest Resources and Environmental Conservation, McLaughlin, Daniel L., Seiler, John R., Strahm, Brian D. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Coverage | Virginia |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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