USGS

Hydrology and tree-distribution patterns of Karst Wetlands at Arnold Engineering Development Center, Tennessee

U.S. Geological Survey, Water Resources Investigations Report 96-4277

by W.J. Wolfe

This report is available as a pdf below


Abstract

Flooding regimes, ground-water interactions, and tree distribution patterns were determined in seasonally flooded sinkhole wetlands at Arnold Engineering Development Center near Manchester, Tennessee.The wetlands are ecologically significant becausethey support coastal-plain plants and animals far from their typical ranges.

Surface-water stage, ground-water levels, rainfall, and streamflow were monitored at or near five wetland sites. Sinking Pond, Willow Oak Swamp, and Westall Swamp are compound sinks with depths greater than 2.5 meters, visible internal drains, and complex bottom topography dominated by coalesced sinkholes and connecting channels. Tupelo Swamp and Goose Pond are karst pans with depths less than 1.5 meters, flat bottoms, and without visible internal drains. Stage rose and fell abruptly in the compound sinks. Maximum water depths ranged from 2.6 meters in Westall Swamp to 3.5 meters in Sinking Pond. Water levels in wells adjacent to Sinking Pond and Westall Swamp rose and fell abruptly, corresponding closely to surface-water stage throughout periods of high water. The two karst pans filled and drained more gradually, but remained flooded longer than the compound sinks. The maximum recorded water depths were 1.1 meters in Tupelo Swamp and 0.7 meter in Goose Pond. Water levels in nearby wells remained lower than the stagein the pans throughout the study period. Tree species were identified and the elevations and diameters of individual trees were measured along 10 transects.Two transects crossed Sinking Pond, two crossed Tupelo Swamp, and one crossed Willow Oak Swamp. The remaining five transects crossed intermittent drainageways that carry flow into or out of Sinking Pond. Transects through ponds had fewer trees but more basal area per unit area of land surface than did transects through channels. Water tupelo (Nyssa aquaticu L.) dominated the interior of Tupelo Swamp and had minimal overlap in terms of elevation and flooding duration with other wetland trees that were confined to the ponds periphery. Overcup oak (Quercus Zyrutu Walt.) dominated the interior of Sinking Pond. Overlap between overcup oak and other wetland trees in terms of elevation and flooding frequency was minimal across the deeper Sinking Pond transect but was substantial across the shallow transect. Willow oak (Quercus phellos L.) dominated the interior of Willow Oak Swamp and had a relation to other wetland trees similar to that of overcup oak in the shallow Sinking Pond transect. Transects acrossbroad swales had a relatively large degree of vertical zonation among wetland and upland tree species.Along transects through well defined channels, elevation distributions of wetland and some upland tree species were grouped near each other and near the distribution of land-surface elevations.

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