ENSURING PLANT SURVIVAL DURING ENVIRONMENTAL STRESS IS NECESSARY TO FEED OUR GROWING HUMAN POPULATION PARTICULARLY IN THE FACE OF FLUCTUATING PRECIPITATION AND TEMPERATURE REGIMES LINKED TO CLIMATE CHANGE. THE RELEASE OF CARBON (C)-RICH ROOT EXUDATES IS A KEY MECHANISM BY WHICH PLANTS MANAGE THE ROOT MICROBIOME TO WITHSTAND ENVIRONMENTAL STRESS, RESULTING IN A C-COST DIVERTED FROM GROWTH AND METABOLISM. THE PROPOSED RESEARCH PROJECT WILL DETERMINE HOW PLANTS AND SOIL MICROBES ADAPTED TO DIFFERENT CLIMATE REGIMES BALANCE THE COST-BENEFIT OF MAINTAINING THE ROOT MICROBIOME UNDER DROUGHT AND HEAT STRESS. I WILL USE A GREENHOUSE EXPERIMENT TO IMPOSE FOUR ENVIRONMENTAL STRESS TREATMENTS ON THE GRASS SPECIES BLUE GRAMA: AMBIENT, HEAT, DROUGHT, HEAT+DROUGHT IN SOILS COLLECTED ACROSS A NATURAL PRECIPITATION GRADIENT. I WILL MEASURE PLANT C ALLOCATION TO GROWTH AND ROOT EXUDATES USING 13CO2-LABELLING AND PLANT PHYSIOLOGY AND DETERMINE HOW STRESS-INDUCED SHIFTS IN C ALLOCATION ALTER THE ACTIVE RHIZOSPHERE USING METAGENOMICS (STABLE ISOTOPE PROBING, SIP). DELIVERABLES WILL INCLUDE ONE PEER-REVIEWED, FIRST-AUTHOR PUBLICATION CONTRIBUTED TO MY DISSERTATION MATERIALS, AND THREE CO-AUTHORSHIPS. THIS PROPOSAL DIRECTLY ADDRESSES THE AFRI PRIORITY AREA OF PLANT HEALTH AND PRODUCTION AND PLANT PRODUCTS AS IT WILL RESULT IN NEW KNOWLEDGE REGARDING THE ADAPTATION OF PLANTS AND MICROBES TO ENVIRONMENTAL STRESSES AND THE CONSEQUENCES OF ALTERED PLANT C ALLOCATION FOR AGRICULTURAL LANDSCAPES. THIS PREDOCTORAL FELLOWSHIP IS RELEVANT TO THE AFRI EWD GOAL OF ADVANCING SCIENCE BECAUSE IT WILL ALLOW ME TO PURSUE MY CAREER GOAL OF IMPROVING AGRICULTURAL SUSTAINABILITY BY DEVELOPING CLIMATE-SMART AGRICULTURAL PRACTICES PRIORITIZING HEALTHY PLANTS AND SOILS.