Nitrogen Cycling Responses to Fire in the Southeastern U.s

I. ABSTRACT Fire can play a significant role in runoff, sediment yield and nutrient transport from aquatic and terrestrial ecosystems in the southeast US. Hydrologic and nutrient cycling interactions with fire are likely to vary considerably across the physiographic regions of the southern U.S.; however, there have been few large comparative studies. Our approach was to combine field measurements and modeling to quantify the impacts of fire on water quality and hydrology at three sites characteristic of the mountain, piedmont and coastal plain regions of the southeastern U.S. We used the nutrient cycling model NuCM (Nutrient Cycling Model) as our platform for predicting nutrient response. Study sites were located in the Nantahala National Forest in the southern Appalachians, the Uwharrie National Forest in the piedmont region and the Croatan National Forest in the coastal plain region. We focused on inorganic nitrogen (NO3, NH4) because it acts as a key indicator of ecosystem response to disturbance and are important water quality parameters. NuCM was parameterized and calibrated with pre-burn data from the three sites. In addition, more severe and intense prescribed fires and wildfire scenarios were modeled by increasing fire effects on parameters that are directly or indirectly altered by fire. In general, both NO3-N and NH4-N concentrations were unaffected by prescribed fire at any level of intensity or severity.