PS 29-156 - Longleaf pine restoration: initial alterations to carbon and water dynamics

Abstract: Widespread management efforts are currently underway to restore longleaf pine (Pinus palustris) dominated systems throughout much of their historical range in the southeastern United States. Longleaf systems have the potential to provide a variety of ecosystem services, including critical wildlife habitat, water resources, and climate- and disturbance-resilient forests. These fire-maintained, savannah-like systems can span from excessively drained to poorly drained soils and present a strong compositional and structural contrast to the short-rotation pine plantations or unmanaged mixed-species stands they are replacing. However, knowledge gaps remain about the immediate effects of the restoration process on hydrology and carbon sequestration, particularly in poorly-drained sites. In this study, we focus on a watershed-scale restoration project at the Santee Experimental Forest on the coastal plain of South Carolina. We use eddy covariance data and streamflow gauging stations from the first growing season following a near-total clearcut to establish a longleaf restoration project and compare it to an adjacent, mature mixed pine/hardwood stand, representing an alternate management state. Despite higher soil temperature in the cut site, ecosystem respiration was only slightly higher than in the mature site. However, higher primary production in the mature stand led it to be a carbon sink, whereas the cut site was a carbon source. Instantaneous evapotranspiration was often similar among the two sites when soil moisture was high, but became lower in the cut site as soil moisture declined. Subsequent work will examine effects of herbaceous growth and longleaf seedling planting in the restoration plots.