OVER THE PAST SEVERAL CENTURIES, ATMOSPHERIC CONCENTRATIONS OF GREENHOUSE GASES (SUCH AS CARBON DIOXIDE, METHANE AND NITROUS OXIDE) HAVE INCREASED SUBSTANTIALLY. THIS INCREASE IS IN PART ATTRIBUTABLE TO EMISSIONS OF GREENHOUSE GASES FROM CROPLANDS, WHICH CURRENTLY OCCUPY ALMOST ONE FIFTH OF THE GLOBAL LANDSCAPE. AS RISING GREENHOUSE GAS CONCENTRATIONS HAVE LED TO WIDESPREAD GLOBAL CHANGES IN CLIMATE, DAMAGES TO ECONOMIES AND DISRUPTIONS TO SOCIETAL FUNCTIONS, THE DEVELOPMENT OF LAND USE SYSTEMS THAT MINIMIZE SOIL GHG EMISSIONS WILL BE CRITICAL TO PREVENTING FURTHER ENVIRONMENTAL, ECONOMIC AND SOCIETAL IMPACTS ASSOCIATED WITH INCREASED ATMOSPHERIC GREENHOUSE GAS CONCENTRATIONS. THE ESTABLISHMENT OF LONG-LIVED PERENNIAL CROPS REPRESENTS A POTENTIAL PATHWAY TO REDUCING CROPLAND SOIL GAS EMISSIONS. INTERMEDIATE WHEATGRASS (IWG; THINOPYRUM INTERMEDIUM, TRADENAME KERNZA &REG;), A COOL-SEASON PERENNIAL GRASS DOMESTICATED FOR GRAIN AND FORAGE PRODUCTION AND THE MOST ADVANCED PERENNIAL GRAIN CROP CURRENTLY UNDERGOING DOMESTICATION, HAS ALREADY BEEN SHOWN TO BETTER PROVISION WATER-RELATED AND SOIL-RELATED ECOSYSTEM SERVICES LARGELY THAN ANNUAL CROPS DUE TO THE DENSE ROOT NETWORKS DEVELOPED BY IWG. HOWEVER, DENSE IWG ROOT SYSTEMS MAY ALSO INCREASE THE CONNECTIVITY AND VOLUME OF SOIL AIR SPACES (I.E. SOIL PORES) AT THE SOIL SURFACE, WHICH MAY IN TURN PROMOTE THE LOSS OF GREENHOUSE GASSES ACCUMULATED THROUGHOUT THE SOIL PROFILE TO THE ATMOSPHERE THROUGH SURFACE SOIL GAS EMISSIONS. WHOLE-YEAR SOIL GAS EMISSIONS, AND THEIR RELATIONSHIP TO SOIL PORE CONSTRUCTION AND HERITABLE ROOT TRAITS REMAINS UNCLEAR IN IWG SYSTEMS, HAMPERING OUR ABILITY TO DEVELOP CLIMATE FRIENDLY CROPPING SYSTEMS FEATURING PERENNIAL GRAINS.THIS PROPOSAL AIMS TO QUANTIFY SOIL GAS EMISSIONS IN PERENNIAL GRAIN AND FORAGE SYSTEMS (IWG, ALFALFA AND IWG-ALFALFA BICULTURE), ELUCIDATE THE RELATIONSHIP BETWEEN SOIL GHG FLUXES (CO2, N2O AND CH4), ROOT TRAITS AND SOIL PORE FEATURES (DERIVED FROM X-RAY IMAGING) IN THESE SYSTEMS; AND EVALUATE THE PLANT GENETIC CONTROLS OVER SOIL GHG EMISSIONS. USING A VARIETY OF METHODS, INCLUDING CAVITY RINGDOWN SPECTROMETRY TO MEASURE SOIL-DERIVED GREENHOUSE GASES AND X-RAY COMPUTED TOMOGRAPHY TO QUANTIFY SOIL PORE NETWORK FEATURES, I WILL ENHANCE OUR UNDERSTANDING OF IWG'S CAPACITY TO MITIGATE SOIL GHG EMISSIONS, WHILE PROVIDING A FOUNDATION OF KNOWLEDGE REGARDING PLANT GENETIC AND ROOT-SOIL CONTROLS OVER SOIL GHG FLUXES, WHICH CAN BE APPLIED TO THE BREEDING AND DEVELOPMENT OF MORE SUSTAINABLE PERENNIAL AND ANNUAL BIOFUEL, GRAIN OR FORAGE CROPS.