CELLULOSIC BIOENERGY CROPS HAVE THE POTENTIAL TO MEET UNITED STATES GREENHOUSE GAS (GHG) REDUCTION TARGETS AND PROVIDE ENERGY SELF-SUFFICIENCY. THE RENEWABLE FUEL STANDARD (RFS) CALLS FOR INCREASING THE VOLUME OF CELLULOSIC BIOFUEL BY 16 BILLION GALLONS WHILE REDUCING LIFECYCLE GHG EMISSIONS BY 60%. CONSIDERATION OF CROP SELECTION, LOCATION, AND MANAGEMENT STRATEGIES IS CRITICAL TO MEET THESE GOALS AND PREVENT ENVIRONMENTAL AND ECONOMIC COSTS FROM OUTWEIGHING BENEFITS. DEPENDING ON THE PRODUCTIVITY OF SELECTED LAND, 33 TO &GT;50 MILLION HECTARES ARE REQUIRED FOR CELLULOSIC BIOENERGY PRODUCTION TO MEET RFS TARGETS. THIS IS ABOUT 25% OF CURRENT U.S. AGRICULTURAL LAND. CONVERTING THIS MUCH LAND INTO BIOENERGY PRODUCTION COMES WITH CHALLENGES INCLUDING ECONOMIC VIABILITY, LANDOWNER WILLINGNESS, AND POTENTIAL ENVIRONMENTAL CONSEQUENCES (E.G. HABITAT LOSS, DEGRADATION, AND CARBON DEBT). BECAUSE A VARIETY OF FACTORS ARE CRITICAL TO A SUCCESSFUL TRANSITION TO CELLULOSIC BIOENERGY, BIOGEOCHEMICAL MODELING PLAYS AN ESSENTIAL ROLE IN ASSESSING POTENTIAL SCENARIOS. MODELS CAN EVALUATE POTENTIAL YIELD, CARBON POOLS AND FLUXES, AND OTHER GHG AND NITROGEN FLUXES (E.G. NITROUS OXIDE AND METHANE EMISSIONS, NITRATE LEACHING) WITH VARYING LANDSCAPES AND MANAGEMENT. THIS RESEARCH USES BIOGEOCHEMICAL MODELING TO EVALUATE THE SUSTAINABILITY OF VARYING BIOENERGY CROPS, LOCATIONS, AND MANAGEMENT TO BETTER INFORM ECONOMIC MODELS AND POLICY DECISIONS TO MEET RFS TARGETS. TO DETERMINE AN EFFECTIVE PATH FOR THE U.S. TRANSITION TO CELLULOSIC BIOENERGY, UNDERSTANDING OF HOW EACH CROP MAY INTEGRATE IN A LANDSCAPE FROM FIELD TO FUEL IS ESSENTIAL. ECOSYSTEM MODELS, LIKE DAYCENT, PROVIDE INSIGHT TO POTENTIAL YIELD AND ECOSYSTEM SERVICES, SUCH AS GHG MITIGATION AND WATER QUALITY, THAT ARE INCORPORATED INTO LIFECYCLE ANALYSES. HOWEVER, REPRESENTATION OF SOIL CARBON DYNAMICS IN MOST MODELS IS OVERSIMPLIFIED WITH DECAY CONSTANT DRIVEN DECOMPOSITION AND SOIL CARBON POOL STRUCTURES THAT DO NOT ALIGN WITHMEASURABLE POOLS OR CURRENT UNDERSTANDING OF SOIL CARBON STABILIZATION. INCREASING MICROBIAL REPRESENTATION IN MODELS HAS SHOWN TO REDUCE UNCERTAINTY OF PREDICTED SOIL CARBON. THIS IS IMPORTANT NOT ONLY FROM A GHG PERSPECTIVE, BUT ALSO BECAUSE SOIL CARBON DYNAMICS ARE INTERTWINED WITH SOIL HEALTH ATTRIBUTES THAT INCREASE LANDSCAPE RESILIENCY (I.E. SOIL FERTILITY, WATER HOLDING CAPACITY, AND EROSION RESISTANCE). THE FIRST OBJECTIVE IS TO INTEGRATE AND EVALUATE SOIL MODEL MODIFICATIONS INTO A VERSION OF DAYCENT THAT WAS RECENTLY UPDATED TO ENCOMPASS PLANT TRAITS SPECIFIC TO PERENNIAL BIOENERGY CROPS.WITH IMPROVEMENTS TO THE SOIL MODEL, DAYCENT WILL BE BETTER SUITED TO EVALUATE YIELD, SOIL HEALTH, AND GHG BALANCES ACROSS LANDSCAPES. IDENTIFYING APPROPRIATE LOCATIONS FOR A PARTICULAR CROP IS PARAMOUNT TO MEETING GHG ATMOSPHERIC LOADING REDUCTIONS, FULFILLING SOCIOECONOMIC NEEDS, AND ACHIEVING SUSTAINABLE LAND USE. IN COMPARISON TO TRADITIONAL AGRICULTURAL CROPS, SOME BIOENERGY CROPS HAVE PHYSIOLOGICAL ATTRIBUTES (E.G. LOW N REQUIREMENTS, HIGH BELOWGROUND BIOMASS, NO TILLAGE) THAT WILL OUTWEIGH THE POTENTIAL NEGATIVES IF PLANTED STRATEGICALLY. HOWEVER, THERE IS STILL MUCH UNCERTAINTY AND CONTROVERSY SURROUNDING WHERE CELLULOSIC BIOENERGY CROPS WILL BE GROWN. CONVERSION OF LAND TO CELLULOSIC BIOENERGY CROPS THAT IS CURRENTLY USED FOR FOOD PRODUCTION RAISES CONCERNS ABOUT FOOD-SCARCITY AND SEQUENTIAL CONVERSION OF UNCULTIVATED LAND CONVERTED FOR FOOD PRODUCTION (INDIRECT LAND-USE CHANGE) RESULTING IN CATASTROPHIC LOSSES OF SEQUESTERED CARBON AND ECOSYSTEM SERVICES THAT WILL NOT BE RECOUPED THROUGH ANNUAL ROW CROP PRODUCTION. CONVERSION OF LAND TO BIOENERGY CROPS THAT IS NOT CURRENTLY USED FOR AGRICULTURAL PRODUCTION ALSO RAISES ENVIRONMENTAL CONCERNS INCLUDING THE EFFECTS ON GHG BALANCES, BIODIVERSITY AND ECOSYSTEM SERVICES, INCREASING REACTIVE NITROGEN THROUGH FERTILIZER, AND WATER USE. THESE POTENTIAL SIDE EFFECTS OF CONVERSION ARE THOUGHT TO BE LARGELY AVOIDED IF BIOENERGY CROPS ARE PRODUCED ON LAND THAT HAS BEEN DEEMED MARGINAL, OR UNPRODUCTIVE LAND THAT WAS USED FOR AGRICULTURE IN THE RECENT PAST. HOWEVER, BECAUSE OF CONSTRAINTS SUCH AS PROXIMITY TO A POTENTIAL REFINERY LOCATION, LANDOWNER WILLINGNESS, AND ECOLOGICAL RISKS, THERE IS NOT ENOUGH IDENTIFIED MARGINAL LAND TO MEET THE 2022 U.S. PRODUCTION MANDATE ESTABLISHED BY THE 2007 ENERGY INDEPENDENCE AND SECURITY ACT. THIS PROJECT WILL EVALUATE LAND THAT IS CURRENTLY IN USE FOR CORN AND SOY PRODUCTION BUT MAY BECOME MARGINAL WITH INCREASING CLIMATE VARIABILITY. THE SECOND OBJECTIVE IS TO IDENTIFY CURRENT CROPLAND THAT IS LIKELY TO EXPERIENCE INCREASED YIELD LOSSES AS A RESULT OF INCREASING FLOODING AND EXTREME PRECIPITATION AND ANALYZE THE POTENTIAL FOR GROWING MORE TOLERANT BIOENERGY CROPS USING THE NEW VERSION OF THE MODEL. CURRENTLY, EMPIRICAL STUDIES OF CELLULOSIC BIOENERGY CROPS ARE LIMITED IN SPATIAL EXTENT AND LONGEVITY. PROCESS-BASED BIOGEOCHEMICAL MODELS INFORMED BY EMPIRICAL STUDIES ALLOW US TO EXTRAPOLATE ECOSYSTEM CARBON AND NITROGEN BALANCES OF VARYING LAND USES (E.G. BIOENERGY CROPS, NATIVE VEGETATION, CONVENTIONAL AGRICULTURE, ETC.) THROUGH SPACE AND TIME. THEY PROVIDE THE OPPORTUNITY TO DEVELOP MORE SUBSTANTIAL HYPOTHESES ABOUT THE ENVIRONMENTAL TRADEOFFS OF BIOENERGY CROPS. IMPROVEMENTS TO PROCESS-BASED MODELS AS NEW EMPIRICALLY BASED DATA EMERGES ARE CRITICAL FOR BETTER INFORMED POLICY AND LAND MANAGEMENT DECISIONS.THROUGH ADVANCES IN SOIL CARBON MODELING AND EXPLORATION OF SOLUTIONS TO BIOENERGY CROP LAND NEEDS WHILE MITIGATING CROP LOSSES, THIS PROJECT DIRECTLY ALIGNS WITH THE BIOENERGY, NATURAL RESOURCES, AND ENVIRONMENT USDA FARM BILL PRIORITY AREA OF THE AFRI EDUCATION AND WORKFORCE DEVELOPMENT RFA. THE PROPOSED RESEARCH ADDRESSES THE PROGRAM GOAL TO ATTAIN BIOFUEL PRODUCTION THAT IS BOTH SUSTAINABLE AND ECONOMICALLY BENEFICIAL FOR AMERICA. THIS PROJECT WILL SEEK LOCATIONS FOR BIOENERGY CROP PRODUCTION THAT MINIMIZE CARBON DIOXIDE, NITROUS OXIDE, AND METHANE EMISSIONS, MAXIMIZE SOIL HEALTH AND SOIL CARBON SEQUESTRATION, AND REDUCE NITRATE LEACHING INTO WATERWAYS, THUS MEETING THE GOAL OF IMPROVING AIR, SOIL, AND WATER QUALITY.