OUR GOAL IS TO EXPLORE PHYSIOLOGICAL PARAMETERS THAT UNDERLIE RESPONSES OF DIFFERENT GENOTYPES AND STAND DENSITIES OF MID-ROTATION LOBLOLLY PINE (PINUS TAEDA) TO DROUGHT. THE WESTERN GULF REGION OF THE USA IS PREDICTED TO EXPERIENCE MORE FREQUENT AND SEVERE DROUGHTS, WHICH CAN SUBSTANTIALLY AFFECT VITALITY OF THE REGION'S ECONOMICALLY SIGNIFICANT LOBLOLLY PINE FORESTS. SINCE THE 1970'S LOBLOLLY PINE GENETIC STOCK FROM THE EASTERN PORTION OF THE SPECIES' NATURAL RANGE HAS BEEN OPERATIONALLY PLANTED IN THE WESTERN GULF BECAUSE EASTERN GENOTYPES OFTEN EXHIBIT FASTER GROWTH AND BETTER FORM THAN LOCAL STOCK. HOWEVER, EASTERN GENOTYPES MAY BE LESS RESILIENT TO DROUGHT. WHILE PLANTING GENOTYPES WITH BETTER DROUGHT HARDINESS CAN MITIGATE DROUGHT PRODUCTIVITY LOSSES AND MORTALITY, AS FORESTS AGE COMPETITION FOR SITE RESOURCES MAKES THEM MORE DROUGHT SUSCEPTIBLE. REDUCING STAND DENSITY BY THINNING CAN IMPROVE DROUGHT RESISTANCE OF LOBLOLLY PINE FORESTS AS THEY REACH THE CANOPY CLOSURE STAGE OF STAND DEVELOPMENT. IN THIS STUDY WE WILL INDUCE DROUGHT AND THINNING TREATMENTS AND MONITOR HYDRAULIC FLUXES, CARBON ASSIMILATION, AND GROWTH TRENDS OF LOBLOLLY PINE GENOTYPES OF DIVERSE ORIGIN (WESTERN AND EASTERN PORTIONS OF THE LOBLOLLY PINE RANGE), STOCK TYPE, GROWTH RATES, AND FORM. OUR OBJECTIVE IS TO QUANTIFY PARAMETERS ASSOCIATED WITH PLANT WATER RELATIONS AND CARBON STATUS AS WELL AS TREE GROWTH, PHENOLOGY, AND BIOMASS ALLOCATION OF LOBLOLLY PINE IN RESPONSE TO THIS COMBINATION OF TREATMENTS TO INFORM PLANTING AND THINNING GUIDELINES FOR THE WESTERN GULF REGION.