Forested peatlands of the Great Dismal Swamp (GDS) have been greatly altered since colonial times, motivating recent restoration efforts. Community structure and function were hydrologically altered by 19th and 20th century ditches installed to lower water levels and enable early timber harvesting. Contemporary forest communities are comprised of maturing remnants from selective timber harvesting that ended in the early 1970s. Red maple (Acer rubrum) has become the dominant species across GDS, encroaching on or replacing the historical mosaic of cypress (Taxodium spp.)/tupelo (Nyssa spp.), Atlantic white-cedar (Chamaecyparis thyoides), and pocosin (Pinus spp.). Moreover, peat soil has been exposed to more unsaturated conditions resulting in carbon loss through decomposition and increased peat fire frequency and severity. Installation of ditch control structures aim to control drainage and re-establish historical hydrology, vegetation communities, peat accretion rates, and fire regime. To help inform restoration and management, we conducted two complimentary studies to test hypotheses regarding hydrologic influences on vegetation, peat depths, and peat fire vulnerability. First, we found thicker peat, lower maple importance, and higher species richness at wetter sites (e.g., higher mean water levels). In our second study, we evaluated the integrated effects of peat properties and water level dynamics on peat fire vulnerability. We found decreased burn vulnerability with increased wetness, suggesting that the driest sites were always at risk to burn, whereas the wettest sites never approached fire risk conditions. Together our findings demonstrate strong hydrologic controls on GDS ecosystem structure and function, thereby informing water level management for restoration goals. / Master of Science / Forested wetlands, like the Great Dismal Swamp (GDS) in eastern Virginia, provide valuable ecosystem services, including wildlife habitat, biodiversity, water quality and storage, carbon storage, and many others. Many of these ecosystems have been lost to land conversion, or hydrologically altered. Ditches installed to lower water levels and enable timber harvesting altered GDS ecosystem services. Lowered water levels changed the forest from a historical mosaic of diverse tree species to a more homogeneous forest dominated by one tree species, red maple. Moreover, GDS’s organic soil (peat) has been exposed to drier conditions resulting in carbon loss through decomposition and increased peat fire frequency and severity. To restore GDS ecosystem services, installation of water control structures in the ditches aim to control drainage and re-establish historical water levels (hydrology), forest cover, peat soil development rates, and fire regime. To help guide this hydrology management, we conducted two complimentary studies to test hypotheses regarding hydrology’s influences on vegetation, peat soil, and peat fire vulnerability. First, we found thicker peat soil, lower red maple prevalence, and more vegetation species at wetter sites. In our second study, we evaluated the integrated effects of peat soil properties and water level dynamics on peat fire vulnerability. We found decreased fire vulnerability with increased wetness, suggesting that the driest site was always at risk to burn, whereas the wettest site never approached conditions for fire risk. Together our findings demonstrate hydrology’s strong controls on GDS ecosystem services, thereby informing water level management for restoration goals.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77701 |
| Date | 22 May 2017 |
| Creators | Schulte, Morgan L. |
| Contributors | Forest Resources and Environmental Conservation, McLaughlin, Daniel L., Aust, W. Michael, Varner, Julian Morgan, Steward, Ryan D. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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