1. Marco A. Galang, Lawrence A. Morris, and Daniel Markewitz D.B. Warnell School of Forestry and Natural Resources, The University of Georgia, DW Brooks Drive, Athens, GA 30602 Potential for Soil Nutrient Mobility After Prescribed Burning in >40-yr-old Loblolly Pine Forest in the Sumter National Forest, South Carolina, USA In pine ecosystems in the Southeastern Untied States, prescribed burning is utilized for site preparation, species control, nutrient recycling, and wildlife management. Effects of prescribed burning on soil and solution chemical attributes have been assessed using paired-watersheds or plot-scale studies. As both of these are dependent on rain events which could occur either shortly after burning or not until the burned area has been covered with fresh fallen litter, results often vary. We conducted an assessment of nutrient mobility in soil before, one week after, and three months after prescribed burning through an artificial leaching experiment. Sampling was done in a >40-yr-old loblolly pine stand at the Long Cane Ranger District, Sumter National Forest. Intact soil core samples were taken before, one week after, and three months after the most recent burn treatment of March 2007. Deionized water was added to soil cores in an amount equivalent to 5 cm of rainfall and the leachate was analyzed for pH, conductivity, dissolved reactive P, K, Ca, and Mg. Separate soil samples were also collected and analyzed for the same soil properties following standard techniques. A soil P fractionation was also included to determine changes in soil P fraction as a result of burning. Results reveal increased soil leachate concentrations of extractable P and cations one week after prescribed burning and back to pre-burn levels three months after burning. This signifies potential for nutrient mobility at the site in the event of immediate rainfall after prescribed burning, although total amounts solubilized were relatively small (e.g., 27 kg-P ha -1 ). MATERIALS AND METHODS We collected 80 soil cores and 40 soil samples before (Pre-burn), a week after (1-Week Post burn), and three months after prescribed burning (3-Month Post burn) in a 3-ha parcel at the Long Cane Ranger District, Sumter National Forest (Figure 1). Cores are either mineral soil only or organic material + mineral soil (char + mineral soil for post burn). RESULTS Soil core extractions were done with intact cores and deionized water leaching (Figure 2). Figure 2. Summary of the soil extraction process and analysis. Deionized water = 5 cm rainfall Intact Soil core Leachate Ca, Mg, K analysis using DIONEX Ion Chromatograph pH and Conductivity Dissolved Reactive Phosphorus using Ascorbic Acid Method and a Manual Spectrometer Separate soil sample Mehlich I extraction Modified Hedley P Fractionation Ca, Mg, K analysis using Flame Atomic Absorption Spectrometer P analysis using Ascorbic Acid Method and a Manual Spectrometer ABSTRACT Figure 1. The loblolly pine stand at the Long Cane Ranger District, Sumter National Forest, South Carolina before and after the prescribed burn of March 13, 2007. Two measured soil temperatures at 2 cm were 100 and 1000 o C. Through soil core leaching, the potential for increased nutrient runoff was demonstrated. This signifies the importance of the timing of rainfall events after prescribed burning in mobilizing nutrients. Despite increased concentrations in runoff chemistry, however, the total content of nutrients in runoff water is low and unlikely to impact non-point source pollution. This increase in soil solution and soil (i.e., HCO 3 -P) concentrations could play an important role in other components of the ecosystem (e.g. microbial growth or plant uptake). CONCLUSION Figure 3. Soil core leachate chemistry (mean±1SD) before (Pre-burn), a week after (1-Week Post burn), and three months (3-Month Post burn) after the prescribed burn treatment at the Long Cane Ranger District, Sumter National Forest, South Carolina. *NA- indicates no data are available because it was impossible to separate the ash from the mineral soil in the 1-Week Post burn OBJECTIVES To determine: a.Potential effects of prescribed burning on nutrient mobility through soil core leaching; and b.Changes in soil P fraction as a result of prescribed burn. Soil core leachates had significant increases in cations, conductivity, and dissolved reactive P one week after the burn. This increase, however, was no longer evident three months after burning (Figure 3). Soil Ca, K, and pH, analyzed following standard techniques, did not increase significantly after the burn (Figure 4). Prescribed burning significantly affected NaHCO 3 extractable inorganic Phosphorus (Figure 5). Figure 5. Soil phosphorus (P) fractions (mean±1SD) before (Pre-burn) and a week after (1-Week Post burn) the prescribed burn treatment at the Long Cane Ranger District, Sumter National Forest, South Carolina. (Pi = Inorganic phosphorus, Po = Organic phosphorus). Figure 4. Soil pH (1:1 water) and Mehlich 1 extractable Ca and K (mean±1SD) before (Pre-burn), a week after (1-Week Post burn), and three months after (3-Month Post burn) the prescribed burn treatment at the Long Cane Ranger District, Sumter National Forest, South Carolina.