Effects of climate variability on forest hydrology and carbon sequestration on the Santee Experimental Forest in coastal South Carolina

Long-term weather and hydrology data from the Santee Experimental Forest were used to assess trends in air temperature, precipitation, and the water balance in gauged watersheds over a 63-year period. Since 1946, the mean annual air temperature has increased at a rate of 0.19 °C per decade, a rate higher than the global mean for the same period. Total annual precipitation has not changed significantly over the period of 1946-2008; however, large storm events (>50 mm precipitation) have increased 21 percent over the 63-year period. Annual stream discharge has varied from 5.5 percent of annual precipitation in dry years to 44.7 percent in wet years. In 1989, much of the forest was destroyed by Hurricane Hugo, a disturbance that, in turn, influenced streamflow. The water balance was estimated using the hydrologic model MIKE SHE; the long-term simulations showed that average annual flow was about 24 percent of annual precipitation and that mean annual evapotranspiration was approximately 76 percent over the 63-year period. The carbon balance on the 500-ha watershed was evaluated using Forest-DNDC. The model performance efficiency was 0.67 for soil CO₂ efflux, 0.70 for soil temperature, 0.40 for soil moisture, and 0.86 for wood biomass dynamics, demonstrating that this model was applicable for predicting carbon dynamics for this complex forest mosaic.