IN THE NEAR-TERM FUTURE, THE POPULATION IS EXPECTED TO RISE, AND CHANGING DIETARY PREFERENCES ARE EXPECTED TO INCREASE FOOD DEMAND BY 25-75%. COINCIDENT WITH THIS INCREASE IN POPULATION, CLIMATE IS ALSO CHANGING -- WITH POTENTIALLY DRASTIC IMPACTS ON FOOD PRODUCTION. A LARGE BODY OF PREVIOUS WORK HAS PROJECTED DECREASES IN CROP YIELD UNDER THIS CHANGING CLIMATE -- LARGELY DUE TO INCREASING TEMPERATURES. MOST STUDIES, HOWEVER, HAVE NEGLECTED THE ROLE OF VAPOR PRESSURE DEFICIT (VPD). A KEY KNOWLEDGE GAP REMAINS FOR HOW CROPS WILL RESPOND TO RISING TEMPERATURES VERSUS INCREASING VPD LEVELS, AND THE INDEPENDENT MECHANISMS THROUGH WHICH THE TWO CLIMATE FACTORS CAN AFFECT YIELD. A QUANTITATIVE UNDERSTANDING OF THESE CLIMATE IMPACTS IS CRITICAL FOUNDATIONAL KNOWLEDGE FOR SELECTING OPTIMAL PLANT TRAITS AND IDENTIFYING MANAGEMENT PRACTICES THAT CAN AID ADAPTATION EFFORTS WITHIN OUR AGRICULTURAL SYSTEMS UNDER A CHANGING CLIMATE.WE WILL USE A PROCESS-BASED CROP SIMULATION MODEL TO SIMULATE MAIZE YIELD RESULTING FROM MANY TRAIT AND MANAGEMENT COMBINATIONS ACROSS THE US AND UNDER FUTURE CLIMATE TREATMENTS. SPECIFICALLY, WE WILL 1)IDENTIFY REGION-SPECIFIC OPTIMAL PLANT TRAITS AND MANAGEMENT PRACTICES THAT LEAD TO MAXIMUM YIELD UNDER CURRENT CLIMATE CONDITIONS; 2)QUANTIFY THE INDEPENDENT AND SPATIALLY VARYING EFFECTS THAT TEMPERATURE AND VPD HAVE ON MAIZE YIELDS IN THE US, AND GAIN A MECHANISTIC UNDERSTANDING OF THE PHYSIOLOGICAL PROCESSES THAT LEAD TO THEIR IMPACTS ON YIELD; 3)IDENTIFY REGIONS THAT ARE VULNERABLE TO YIELD LOSS UNDER FUTURE CHANGES IN TEMPERATURE AND VPD, AND INVESTIGATE THE POTENTIAL IMPACT OF MITIGATION AND ADAPTATION THROUGH CULTIVAR SELECTION AND SHIFTS IN MANAGEMENT PRACTICES.WE WILL COMMUNICATE OUR FINDINGS THROUGH SCIENTIFIC CONFERENCES AND PEER-REVIEWED PUBLICATIONS. THE OUTCOME OF THIS RESEARCH WILL BENEFIT US AGRICULTURE BY EQUIPPING BREEDERS, CROP SCIENTISTS, POLICYMAKERS, AND AGRONOMISTS, WITH LOCALIZED CULTIVAR AND MANAGEMENT TARGETS AND PRIORITIES TO ADAPT TO IMPENDING CLIMATE STRESSORS.