DROUGHT IS ONE OF THE MOST HARMFUL WEATHER DISASTERS WITH RESPECT TO AGRICULTURAL PRODUCTIVITY IN THE US, WITH THE ECONOMIC COSTS OF THESE EVENTS EXPECTED TO INCREASE AS DROUGHTS ARE MORE FREQUENT AND INTENSE IN THE FUTURE. IMPROVED UNDERSTANDING OF HOW THE SOIL MICROBIOME (E.G., BACTERIA AND FUNGI THAT INHABIT THE SOIL ENVIRONMENT) RESPONDS TO INCREASED FREQUENCY AND INTENSITY OF DROUGHT MAY PROVIDE INSIGHT VALUABLE FOR MITIGATING THESE LOSSES AND SUSTAINING AGRO-ECOSYSTEM FUNCTIONS. RANGELANDS, WHICH PROVIDE VALUABLE ECOSYSTEM SERVICES SUCH AS FORAGE PRODUCTION FOR LIVESTOCK, ARE PARTICULARLY PRONE TO DROUGHT. RECENT RESEARCH SUGGESTS THAT BOTH PLANTS AND SOIL MICROBES RESPOND STRONGLY TO EXPERIMENTAL DROUGHT IN US RANGELANDS. THUS, OUR GOAL IS TO ASSESS HOW DROUGHT-INDUCED CHANGES IN SOIL MICROBES AND THE INTERACTION BETWEEN PLANTS AND SOIL MICROBES INFLUENCES IMPORTANT ECOSYSTEM SERVICES, SUCH AS FORAGE PRODUCTION. WE WILL USE EXISTING EXPERIMENTAL INFRASTRUCTURE TO IMPOSE DROUGHT IN THREE MAJOR RANGELANDS OF THE CENTRAL US - SHORTGRASS STEPPE IN NORTHEASTERN CO, MIXED GRASS PRAIRIE IN WESTERN KS, AND TALLGRASS PRAIRIE IN NORTHEASTERN KS. FOR EACH RANGELAND, WE WILL COMPARE HOW PLANTS AND SOIL MICROBES RESPOND TO DROUGHT OVER TIME, ASSESS HOW CHANGES IN THE SOIL MICROBES AFFECTS THE MOST ABUNDANT GRASS SPECIES IN EACH RANGELAND AND VICE VERSA, AND QUANTIFY HOW RESPONSES OF PLANTS AND SOIL MICROBES TO A DROUGHT AFFECT FUTURE RESPONSES TO DROUGHT. OUR PROPOSED RESEARCH ADDRESSES THE CORE OBJECTIVES OF THE AGRICULTURAL MICROBIOMES PROGRAM AREA PRIORITY BY CHARACTERIZING AGRICULTURAL MICROBIOMES, MICROBIOME FUNCTIONS AND HOST-MICROBIOME INTERACTIONS THAT CONFER DROUGHT TOLERANCE.