Evapotranspiration of a Mid-rotation Loblolly Pine Plantation and a Recently Harvested Stands on the Coastal Plain of North Carolina, U.s.a

Evapotranspiration (ET) is the primary component of the forest hydrologic cycle, which includes plant transpiration, canopy rainfall interception, and soil evaporation. Quantifying ET processes and potential biophysical regulations is needed for assessing forest water management options. Loblolly pines are widely planted in the coastal plain of the Southeastern US, but their water use is rarely directly measured. This study aims to quantify ecosystem ET and its components by direct measurements of sap flow, canopy interception, and eddy fluxes. Our research sites included a 13year old loblolly pine plantation and a recently harvested stand on Weyerhaeuser’s Parker Tract in Washington County, eastern North Carolina. Sap flow data were collected with sensors at different sapwood depths and circumferential positions for 8 loblolly pines using thermal dissipation probes. Sapflow flux measured at individual trees was scaled up to the stand level. Sap flow flux density was empirically correlated to meteorological factors to examine the biological and physical controls. Precipitation above tree canopy, throughfall, and stem flow were measured to quantify canopy interception. Two separate flux towers at the centers of two stands were installed in measure eddy flux for water and carbon fluxes and microclimate since October 2004. Comparisons of ET estimates between sapflow methods and the eddy covariance method showed a 20% difference. Recently-cut stand had similar ET as the mid-rotation plantation stand.