** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** DEVELOPMENT OF NEW BIOENERGY CROPS HAS THE POTENTIAL TO REDUCE CONSUMPTION OF FOSSIL FUELS WHILE ALSO ENHANCING ENVIRONMENTAL BENEFITS, INCLUDING THROUGH BUILDING BELOWGROUND SOIL CARBON STOCKS. SWITCHGRASS, A MEMBER OF NORTH AMERICAN TALLGRASS PRAIRIE, HAS BECOME A PROMISING FEEDSTOCK FOR BIOENERGY PRODUCTION. YET, IT IS NOTORIOUSLY SLOW IN GENERATING SOIL CARBON GAINS. WE ENVISION TWO SOLUTIONS TO THIS PROBLEM: 1) BREEDING SWITCHGRASS TO HAVE HIGHER CAPACITY TO BUILD SOIL CARBON, AND 2) DEVELOPING SWITCHGRASS CROPPING SYSTEMS THAT INCLUDE OTHER PLANT SPECIES TO ENHANCE THE STABILIZATION OF CARBON IN THE SOIL. TO EXPLORE THE FEASIBILITY OF THESE SOLUTIONS, WE NEED TO GAIN A BETTER UNDERSTANDING OF HOW SWITCHGRASS ROOT SYSTEMS AND SOIL MICROORGANISMS INTERACT WITH SOIL PORE STRUCTURE, AND HOW THIS INTERACTION RESULTS IN STABILIZATION OF THE FIXED CARBON THAT SWITCHGRASS ALLOCATES BELOWGROUND.WE WILL PERFORM AN IN-DEPTH ANALYSIS OF THE ROOT BIOMASS AND STRUCTURE, MICROBIAL SYMBIONTS, SOIL PORES, AND RESULTING SOIL CARBON ACCUMULATION IN TWO EXPERIMENTS. IN THE FIRST, WE WILL COLLECT DATA FROM 18 SWITCHGRASS GENOTYPES GROWN IN THE FIELD AT THREE LOCATIONS (IN MI, MO, AND TX). IN THE SECOND, WE WILL COLLECT DATA FROM A FIELD EXPERIMENT IN WHICH SWITCHGRASS IS GROWN WITH NINE OTHER SPECIES AS NEIGHBORS, INCLUDING NATIVE SPECIES OF GRASSES, FORBS, AND LEGUMES. THIS STUDY WILL PROVIDE KNOWLEDGE ABOUT HOW SOIL STRUCTURE, WHICH IS CRITICAL FOR PROTECTION OF CARBON IN SOIL, IS AFFECTED BY SWITCHGRASS ROOTS AND MICROBIAL SYMBIONTS. IN ADDITION, WE WILL BE ABLE TO ASSESS THE MOST PROMISING TRAITS FOR PLANT BREEDING, AND THE MOST PROMISING ADDITIONAL PLANT SPECIES FOR A MULTI-SPECIES CROPPING SYSTEM, WITH THE GOAL OF ENHANCED SOIL CARBON SEQUESTRATION. THE RESULTS OF THIS STUDY WILL BENEFIT SOCIETY BY PROVIDING KNOWLEDGE NEEDED TO DESIGN BIOENERGY CROPPING SYSTEMS THAT HAVE BOTH HIGH PRODUCTIVITY AND CAN CAPTURE CARBON FROM THE ATMOSPHERE.