PARENT SESSION
Oral Session #70: Riparian Ecology. Presiding: R. Cosgriff.
Thursday, August 9, 2001. 1:00 PM to 4:45 PM. Hall of Ideas I.
Fluvial geomorphology and biodiversity of forested wetlands along two tributaries of the Chesapeake Bay.
Alexander, Lauren 1, 2, Ross, Katie2, 3, Hupp, Cliff2, Forman, Richard1, 1 2 3
ABSTRACT- Vegetation of forested wetlands or floodplains can be described as a mosaic driven partially by overbank flows, hydroperiod, and floodplain surface heterogeneity. In this research, hydrogeomorphic conditions are investigated as potential indicators of plant diversity and composition in forested wetlands on a longitudinal gradient along the Chickahominy and Pocomoke Rivers, two tributaries on the Coastal Plain of the Chesapeake Bay. We characterize site hydrology, geomorphology, and vegetation, and describe and spatially represent physical conditions, site surface heterogeneity and vegetation. The floodplain surfaces were surveyed in 100 x 100 m grids at three characteristic sites along each river, and woody and herbaceous species were tallied using quarter point measurements and 400 m2 plots. Hydroperiod values were calculated from USGS gaging station records and field observations. Along the Chickahominy River, we found strong upstream-to-downstream trends: increases in length of hydroperiod (from 3.5 days/yr to more than 45), total species richness (17 to 24), woody diversity using the Shannon-Weiner diversity index (0.51 to 1.95), and surface heterogeneity (elevation range from 1.1 to 2.4 m, standard deviation from 0.24 to 0.51); and decreases in deposition rates (1.9 to 0.9 mm/yr), percent sand deposition (high to low), and number of discrete debris piles (12 to 0). A comparison of Chickahominy trends and Pocomoke patterns suggests that many factors, including longitudinal gradient, may relate to biodiversity in Chesapeake Bay forested wetlands.
KEY WORDS: Forested Wetland, Fluvial geomorphology, Biodiversity, Floodplain