A NEW MODEL FOR SOUTHERN APPALACHIAN WETLAND EVOLUTION

Naturally occurring wetlands are scarce in the Appalachian Mountains of North Carolina, Tennessee, and areas to the south. The few wetlands that were present pre-settlement have largely been altered by humans. Those that remain today are small, isolated systems usually found in stream valleys, or as seepage wetlands on mountain slopes, or occasionally related to local karst topography. In an effort to better understand the origin and evolution of these wetland systems, a wetland inventory was conducted in Great Smoky Mountains National Park, which straddles the North Carolina/Tennessee state line. Wetland areas in the park were initially located and described. Monitoring wells were installed in 10 sites. Water levels were monitored on a monthly basis. Twelve sites were chosen for detailed water and soil chemistry analysis. Water samples were collected monthly and analyzed for Ca, Mg, Na, K, P, pH, DO, and conductivity. Samples were collected from both the hydrologic in-flow and out-flow of each site (where possible). Soil samples were collected seasonally and analyzed for Ca, Mg, Na ,K P, and loss-on-ignition (LOI). None of the study sites are peat accumulating environments. Average values for all of the sites indicate that these wetlands are nutrient poor; yet, they have relatively high pH values, similar to those of rich-fens. Hydrologically, most sites are seepage-controlled, groundwater fed, with a handful situated in sinkholes and other karst features. Cluster analysis of the chemistry data groups the wetlands on the North Carolina side of the park separately from those on the Tennessee side. This is concluded to be a result of bedrock control of groundwater chemistry. Finally, all of these wetland sites appear to be ephemeral features on the southern landscape. During dry years (e.g 1999), many wetlands dry up during the summer and are invaded by upland vegetation. The fact that these systems have almost no organic layer is an indication that the water table is frequently drawn down. It is proposed that the number of wetlands existing on the landscape in the southern Appalachians is directly related to decadal/millenial scale changes in climate. Preliminary analysis suggests that those wetlands at high elevation and those located at low elevation but adjacent to steep slopes are the most persistent.