**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** OAK SAVANNAS ARE AN IMPORTANT VEGETATION TYPE IN THE SOUTHERN USA, MAKING UP MORE THAN 120,000 KM2.OVER THE PAST 150 YEARS, THESE LANDSCAPES HAVE BEEN RADICALLY TRANSFORMED BY CULTIVATION AND SUBSEQUENT ABANDONMENT, ALTERED FIRE REGIMES, URBANIZATION, AND FRAGMENTATION. THIS ALTERED FIRE REGIME HAS ALLOWED UNDESIRABLE PLANTS TO INVADE THE UNDERSTORY, CREATING DENSE THICKETS OF VEGETATION--A PROCESS DESCRIBED BY SOME AS THICKETIZATION.THE OVERARCHING GOAL OF OUR PROPOSED PROJECT IS TO DEVELOP A BETTER UNDERSTANDING OF THE ECOHYDROLOGICAL IMPLICATIONS OF THICKETIZATION IN OAK SAVANNAS. WE ARE PARTICULARLY INTERESTED IN DETERMINING IF GROUNDWATER RECHARGE COULD BE ENHANCED VIA THE CREATION OF A MORE OPEN STRUCTURE. WE WILL FOCUS OUR FIELD STUDIES ON THE POST OAK SAVANNA ECOREGION IN EASTERN TEXAS. WE BELIEVE THAT THIS ECOREGION HOLDS PARTICULAR PROMISE FOR INCREASING GROUNDWATER RECHARGE AT A REGIONAL SCALE BECAUSE ABOUT ONE-THIRD OF ITS AREA IS UNDERLAIN BY THE DEEP SANDY SOILS OF THE CARRIZO-WILCOX RECHARGE ZONE. WE WILL EMPLOY A VARIETY OF FIELD MEASUREMENTS AT TWO LOCATIONS IN THE POST OAK SAVANNA, ALL OF WHICH ARE DESIGNED TO BETTER QUANTIFY WATER FLUXES ACROSS THESE LANDSCAPES (ESPECIALLY RECHARGE). USING BOTH REMOTE SENSING AND HYDROLOGICAL MODELING, WE WILL BE ABLE TO SCALE UP OUR RESULTS TO THE ENTIRE REGION AND APPLY THEM TO OTHER OAK SAVANNAS. A SECONDARY BUT VERY IMPORTANT GOAL OF THIS PROJECT IS TO ADVANCE ECOHYDROLOGY RESEARCH OPPORTUNITIES FOR EARLY- CAREER SCIENTISTS AND UNDERGRADUATE STUDENTS.THE PROJECT WILL SUPPORT ONE FULL TIME POST-DOCTORAL SCIENTIST AND HEAVILY INVOLVE THREE PH.D. STUDENTS.