HOLOCENE HYDROCLIMATE AND FIRE VARIABILITY IN THE GREAT DISMAL SWAMP, SOUTHEASTERN VIRGINIA, USA

The Great Dismal Swamp (GDS) originally covered more than a half million acres in Virginia and North Carolina, but logging, ditching, and road construction beginning in the 18^th century reduced its extent to ~100,000 acres. Recent management activities have focused on wetland resilience and restoration, and a fundamental science need is an understanding of how climate variability and human alteration of the landscape combined to affect 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 up to the last ~14,000 years. Collectively, these sites record the initial deglacial presence of cool-temperate forests dominated by Quercus and Fagus, with common Picea glauca. By about 12,000 years ago, the presence of marsh vegetation is indicated by the dominance of grass pollen and presence of Nymphaea and Sagittaria. The marsh phase persisted until about 3,500 cal yr BP, and fluctuations in marsh composition and charcoal abundance indicate the frequent occurrence of fires in the early and middle Holocene. Around 3,500 cal yr BP, forested wetlands developed across GDS, dominated by Nyssa and Taxodium with common Acer, Ilex, and, locally, Chamaecyparis. An increase in Cupressaceae abundance ~3,000-2,000 cal yr BP, followed by greater abundance of Nyssa, is suggestive of changes in rates and patterns of streamflow. Rare occurrence of charcoal throughout the Nyssa-Cupressaceae interval indicates that fires were infrequent in GDS during the late Holocene. 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.