**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** RESTORING DEPLETED SOIL CARBON (C) CAN PARTIALLY OFFSET FOSSIL FUEL EMISSIONS, IMPROVE SOIL HEALTH, AND HELP MEET FUTURE AGRICULTURAL DEMANDS. ONE AVENUE TO RESTORE SOIL C IS REESTABLISHING NATIVE GRASSLAND DIVERSITY IN LANDS THAT WERE ONCE USED FOR AGRICULTURE. HOWEVER, OVER TIME GRASSLAND SOILS BOTH TAKE UP AND LOSE C, MAKING IT DIFFICULT TO PREDICT WHEN OUR EFFORTS WILL SUCCESSFULLY OFFSET FOSSIL FUEL EMISSIONS. SOIL RESPIRATION IS THE PROCESS BY WHICH SOILS LOSE C, AND AS SUCH IT REPRESENTS A LENS THROUGH WHICH WE CAN ASSESS WHETHER GRASSLAND SOILS MIGHT GAIN SOIL C. WHILE WE KNOW HOW ENVIRONMENTAL CONDITIONS LIKE SOIL MOISTURE AND TEMPERATURE AFFECT SOIL RESPIRATION, WE KNOW MUCH LESS ABOUT HOW CHANGES IN PLANT COMMUNITIES AFFECT SOIL RESPIRATION AND FURTHERMORE, HOW BOTH PLANT COMMUNITIES AND SOIL RESPIRATION MIGHT BE ALTERED WITH CHANGING PRECIPITATION. FROM PREVIOUS USDA-FUNDED RESEARCH, WE FOUND GRASS-DOMINATED COMMUNITIES EXHIBIT HIGHER SOIL RESPIRATION RATES THAN OTHER COMMUNITIES, ESPECIALLY IN WETTER CONDITIONS. THESE FINDINGS ALSO SUGGEST THAT THE SPECIFIC TYPE OF PLANTS PRESENT INTERACTS WITH ALTERED PRECIPITATION TO INFLUENCE SOIL C LOSS. THE FORCES DRIVING THESE RESULTS, HOWEVER, REMAIN UNCLEAR, WHICH IS WHAT THIS RESEARCH BEGINS TO ADDRESS. THROUGH LAB AND GREENHOUSE EXPERIMENTS PAIRED WITH AN ESTABLISHED PRECIPITATION AND PLANT DIVERSITY MANIPULATION EXPERIMENT THAT ALTERS BOTH THE NUMBER OF PLANT SPECIES AND WHICH SPECIES ARE PRESENT IN A COMMUNITY, WE PROPOSE TO TEST HOW PLANT ROOTS INFLUENCE C LOSS FROM GRASSLAND SOILS.WE FIRST EXPLORE WHETHER THE DEATH AND DECAY OF ROOTS, ROOT DECOMPOSITION, IS ONE OF THE FORCES DRIVING INCREASED SOIL RESPIRATION IN GRASS COMMUNITIES. TO DO SO, WE WILL MONITOR THE LOSS OF ROOTS FROM MESH BAG BURIED IN THE PLOTS AND BY COMPARING THE CHANGE IN WEIGHT OVER TIME TO SOIL RESPIRATION WE WILL BE ABLE TO DETERMINE WHETHER ROOT DECOMPOSITION IS ONE OF THE FORCES GOVERNING C LOSS FROM SOILS. GRASSES MAY ALSO INFLUENCE MICROBIAL COMMUNITY RESPIRATION BY SECRETING COMPOUNDS, ROOT EXUDATES, THAT STIMULATE MICROBIAL COMMUNITIES TO BREAK DOWN OLDER ORGANIC MATERIALS ALREADY IN SOILS. WE WILL, SECONDLY, COLLECT ROOT EXUDATES DIRECTLY FROM PLANTS GROWN IN A GREENHOUSE AND APPLY THEM TO COMMON SOILS TO MONITOR SOIL C LOSE OVER TIME. WE WILL LIKEWISE COLLECT SOIL POREWATER, WHICH CONTAINS EXUDATES IN OTHER ADDITIONAL COMPOUNDS, AND USE THE SAME METHOD TO SEE IF SAMPLES COLLECTED FROM THE FIELD AND SAMPLES ISOLATED FROM A GREENHOUSE GENERATE THE SAME RESULTS. THIS WORK WILL HELP US BEGIN TO UNRAVEL HOW THE COMPLEXITIES OF BIOLOGICAL COMMUNITIES, BOTH WHICH PLANTS ARE PRESENT AND HOW MANY, INTERACT WITH ALTERED PRECIPITATION REGIMES TO HELP MITIGATE C LOST FROM SOILS AND HELP US IMPROVE OUR ABILITY TO REESTABLISH SOIL C ON PREVIOUSLY CULTIVATED LANDS. SINCE GRASSLANDS REPRESENT ALMOST 40% OF TERRESTRIAL SURFACE AREA, IT IS IMPORTANT TO UNDERSTAND THE RELATIONSHIP BETWEEN GRASS COMMUNITIES, SOIL C STORAGE, AND C,HANGING PRECIPITATION. OUR WORK WILL ALSO BE OF INTEREST FOR STAKEHOLDERS MANAGING BIOFUEL CROPS. SWITCHGRASS, A COMMON GRASS CHOSEN FOR BIOENERGY FEEDSTOCKS, WAS SPECIFICALLY SELECTED FOR EXPERIMENTS. OFTEN BIOENERGY FEEDSTOCKS, LIKE SWITCHGRASS, ARE GROWN IN WITHOUT A DIVERSITY OF NEIGHBORING PLANTS, WHICH COULD LIMIT THEIR ABOVEGROUND GROWTH AND ABILITY TO STABILIZE SOIL C. OUR WORK WILL PROVIDE USEFUL GUIDANCE ON HOW BEST TO GROW BIOENERGY STOCKS, SUCH AS SWITCHGRASS, TO MINIMIZE C LOST FROM THEIR SOILS AND TO MAXIMIZE THEIR ABILITY TO SEQUESTER C IN STABLE FORMS.?