HYDROLOGIC RESPONSE TO FIRE AND DROUGHT IN A SOUTHERN APPALACHIAN WETLAND

This presentation will focus on hydrologic data collected at a Southern Appalachian fen in Clay County, North Carolina. This 5-acre, groundwater-fed wetland was purchased by the Nature Conservancy in 1988 to protect the only known population of Sarracenia oreophilia (a federally-endangered pitcher plant) in the state. The site is underlain by approximately 10 feet of clayey stream deposits (K=0.05 ft/d) above gravel and/or competent bedrock. Groundwater wells were installed in the mid-1990s and have been monitored at varying frequencies since that time. In general, the water table fluctuates throughout the year, with higher water levels in the winter-spring and lower levels in the summer-fall. During wetter years, the water table remained at or near the ground surface for much of the year, with the clay layer underlying the site retaining moisture even after the water table has dropped. However, the “clay wetting” period was shorter during dryer years (drought years 1999-2000 and 2007-2008 in particular) and corresponded with a reduction in the number of pitcher plant clumps observed at the site.

In addition to the geologic and climatic controls on hydrology, the site has been subject to controlled burns since the early 1900s. Previous land owners used fire to maintain open space for grazing cattle, and The Nature Conservancy has continued the practice to combat woody vegetation and open the canopy. The most recent controlled burn was completed in April 2015, which reduced evapotranspiration, led to a rapid 0.35-0.96 ft (0.1-0.3m) rise in water levels across the site, and resulted in a thriving Sarracenia population. Drought conditions returned in the second half of 2016, however, along with the lowest recorded water levels at the site since 2008.