Holocene records of wetland hydrology and fire in Great Dismal Swamp (Virginia and North Carolina, USA): documenting natural variability and human impacts
Abstract
The Great Dismal Swamp (GDS) originally covered more than one million acres in Virginia and North Carolina, but logging, ditching, and road construction beginning in the 18th century reduced its extent to ~100,000 acres. Among needs of resource manager are improved understanding of wetland resilience under various management and climate scenarios. To address this need, we generated new sedimentary records from the Refuge to document how Holocene patterns of climate variability and human alteration of the landscape combined to influence hydrology, native vegetation, and fire regimes. We present new records of pollen, plant macrofossils, macroscopic charcoal, and physical properties from six sites in GDS that span the last ~14,000 years. Collectively, these sites record the initial deglacial presence of cool-temperate forests dominated by oak and beech, with common white spruce. By about 11,000 years ago, marshes with abundant grasses and varying amounts of waterlily, sedge, and other marsh taxa were established in wetlands along stream courses. Fluctuations in marsh composition and charcoal abundance throughout the marsh phase indicate the frequent occurrence of fires in the early and middle Holocene. Between ~4,000 and 3,000 years ago, forested wetlands blanketed GDS, dominated by tupelo and cypress with common maple, holly, and, locally, Atlantic white cedar. An increase in cypress abundance ~3,000-2,000 years ago, followed by greater abundance of tupelo, is suggestive of changes in rates and patterns of streamflow. The rare occurrence of charcoal throughout the tupelo-cypress interval indicates that fires were infrequent in GDS during the late Holocene. During the last few centuries, we observed shifts from tupelo-cypress forests to modern pine pocosin and maple-gum forests, suggesting that Colonial-era ditching and drainage of the swamp played a significant role in determining distribution of modern vegetation. Comparison of late Holocene records with those of the last few centuries provides insights on the relative roles of hydroclimate, drainage beginning in the Colonial era, and other environmental stressors on the distribution and composition of wetland communities of the Great Dismal Swamp.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB052.0003W
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0497 Wetlands;
- BIOGEOSCIENCES;
- 4950 Paleoecology;
- PALEOCEANOGRAPHY