THE CENTRAL GRASSLANDS OF THE MIDWEST, WHICH CONTRIBUTE $10 BILLION IN AGRICULTURAL ANNUALLY TO KANSAS ALONE, ARE DOMINATED BY THE PERENNIAL GRASS ANDROPOGON GERARDII. THIS FOUNDATIONAL GRASS SPECIES COMPRISES UP TO 80% OF GRASSLAND BIOMASS AND IS HEAVILY IMPACTED BY DROUGHT. GIVEN THAT DROUGHT FREQUENCY IS EXPECTED TO INCREASE, MANAGING FOR RESILIENCY IN THIS CRITICAL ECOSYSTEM REQUIRES UNDERSTANDING HOW A. GERARDII RESPONDS TO DROUGHT. DESPITE THE IMPORTANCE OF ANDROPOGON GERARDII TO NATURAL PRAIRIES AND MANAGED RANGELANDS, WE KNOW LITTLE ABOUT THE LINKAGES BETWEEN THESE COMPONENTS AND PROCESSES. WE KNOW EVEN LESS ABOUT THE POTENTIAL FOR ESTABLISHMENT OF NEW PLANT HOST POPULATIONS AND THEIR RHIZOBIOMES UNDER ANTICIPATED SCENARIOS OF ENVIRONMENTAL CHANGE WITH IMPLICATIONS FOR GRASSLAND RESTORATION. INCREASING EVIDENCE SUGGESTS THAT THE RESPONSES OF PLANTS TO DROUGHT ARE MEDIATED BY SOIL MICROBIAL PROCESSES. THUS, DESIGNING APPROPRIATE MANAGEMENT STRATEGIES TO INCREASE RESILIENCY TO DROUGHT WILL REQUIRE UNDERSTANDING UNDERLYING ECOTYPIC VARIATION IN A. GERARDII, HOW THIS RELATES TO SOIL MICROBIAL COMMUNITIES AND SOIL PROCESSES, AND THE DEGREE OF MATCH BETWEEN HOST AND SOIL MICROBES. IT WILL ALSO REQUIRE ANTICIPATING SHIFTS IN THE PLANT-SOIL MICROBE RELATIONSHIP AS CONDITIONS CHANGE.WE AIM TO ELUCIDATE THE INTERACTION BETWEEN PLANT HOST AND ITS ASSOCIATED RHIZOBIOME BY EXAMINING THE RHIZOBIOME COMPOSITION AND FUNCTION, NUTRIENT CYCLING, PLANT GENETICS, PLANT PHENOTYPE, AND PLANT GENE EXPRESSION. TO DO THIS, WE WILL USE A SET OF COMPLEMENTARY FIELD AND GREENHOUSE EXPERIMENTS, BROAD GEOGRAPHIC SAMPLING OF NATURAL GRASSLANDS ACROSS THE GREAT PLAINS, AND SEVERAL MODELING AND APPROACHES. WE WILL INTEGRATE MULTI-OMICS DATA, PLANT PHENOTYPE AND GENOTYPE ANALYSES, AND MICROBIALLY MEDIATED PROCESSES THROUGH A MIXED MODEL. FINALLY, WE WILL EXPLOIT RHIZOBIOME FUNCTIONS, STRUCTURAL EQUATION MODELING (SEM) AND SPATIAL MODELING TO PREDICT HOW ECOTYPE VARIATION WILL AFFECT RHIZOBIOME INTERACTIONS AND MICROBIALLY MEDIATED PROCESSES ACROSS THE GREAT PLAINS. THE OUTCOME WILL BE A MORE COMPLETE UNDERSTANDING OF HOW PLANT GENETIC DIVERSITY AFFECTS RHIZOBIOME COMPOSITION AND FUNCTION, AND IN TURN MICROBIALLY MEDIATED PROCESSES. HERE WE PROPOSE TO 1) QUANTIFY THE RELATIONSHIP BETWEEN THE PLANT ECOTYPE, ASSOCIATED RHIZOBIOME, AND MICROBIALLY-MEDIATED SOIL PROCESSES; 2) TEST WHETHER MISMATCHES BETWEEN HOST ECOTYPE AND RHIZOBIOME AFFECT PLANT FITNESS AND DROUGHT; 3) DETERMINE IF THE OBSERVED PLANT GENETIC DIVERSITY IN PLANT POPULATIONS IN NATURAL PRAIRIES ACROSS THE GREAT PLAINS FEEDS BACK TO AFFECT RHIZOBIOME COMPOSITION AND SOIL PROCESSES; AND 4) PREDICT CURRENT AND FUTURE RESPONSES OF PLANT-MICROBE-SOIL PROCESSES TO DROUGHT AND TEMPERATURE.WE WILL ACCOMPLISH THIS RESEARCH BY INTEGRATING TRANSDISCIPLINARY EXPERTISE IN ECOLOGICAL GENOMICS, BIOINFORMATICS AND COMPUTATIONAL SCIENCE, MICROBIOME DIVERSITY AND FUNCTION, ECOSYSTEM PROCESSES, AND SPATIAL DISTRIBUTION MODELING. THIS RESEARCH WILL HELP CHARACTERIZE A. GERARDII ECOTYPE RESPONSES TO FUTURE CHANGING CLIMATES AND WILL IDENTIFY IF LOCAL ADAPTATION TO CLIMATE AND THE RHIZOBIOME LIMITS THIS SPECIES' ABILITY TO ADJUST TO CHANGING CLIMATE, OR IF POPULATIONS HAVE POTENTIAL TO MIGRATE (OR BE RESTORED) TO MATCH FUTURE CLIMATE CONDITIONS. ULTIMATELY, OUR RESULTS WILL INFORM CONSERVATION AND RESTORATION MANAGERS TO BETTER IDENTIFY THE OPTIMAL REGIONAL ECOTYPES AND SOIL THAT OPTIMIZES PRODUCTIVITY AND ECOSYSTEM PROCESSES UNDER DIFFERENT CLIMATE SCENARIOS.OUR WORK WILL BE CRITICAL FOR ENSURING THE ECONOMIC INTEGRITY AND ENHANCING RESILIENCY OF THIS ECONOMICALLY VITAL ECOSYSTEM.