POTENTIAL CLIMATE-CHANGE EFFECTS ON LOBLOLLY-PINE FOREST PRODUCTIVITYAND DRAINAGE ACROSS THE SOUTHERN UNITED-STATES

PnET-IIS, a well validated, physiologically based, forest ecosystem mo del combined soil and vegetation data with six climate change scenario s. The model predicted annual net primary productivity and drainage on loblolly pine sites in the southern US states of Texas, Mississippi, Florida and Virginia. Climate scenario air temperature changes were +2 degrees C to +7 degrees C > historic (1951 to 1984) values and climat e scenario precipitation changes were -10% to +20% > historic values. Across the sites, increasing air temperature would have much greater i mpact on pine forest hydrology and productivity than would changes in precipitation. These changes could seriously impact the structure and function of southern United States forests by decreasing net primary p roductivity and total leaf area. Water use per unit area would increas e, but total plant water demand would decrease because of reduced tota l leaf area, thus increasing regional pine forest drainage. An average annual air temperature increase of 7 degrees C, caused a considerable reduction in the loblolly pine range.