** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE LONGLEAF PINE (LLP) SAVANNA OF THE SOUTHEAST US COVERS A MERE 3% OF ITS ORIGINAL 92-MILLION ACRES AND IS IN DIRE NEED OF RESTORATION. AS A FIRE DEPENDENT ECOSYSTEM, PRODUCTIVITY OF THE UNDERSTORY VEGETATION ENABLES FIRE SPREAD, MAINTAINING ECOSYSTEM HEALTH AND FUNCTION. THUS, THE VEGETATION-FIRE FEEDBACK LOOP IS A PRIMARY RESTORATION GOAL. YET FIRE ALSO CREATES RESOURCE CONSTRAINTS AS NITROGEN (N) IS LOST TO THE ATMOSPHERE DURING BIOMASS BURNING. LEGUME PLANTSHAVE THE POTENTIAL TO OVERCOME N-LIMITATION THROUGH FORMING A SYMBIOSIS WITH N-FIXING BACTERIA (RHIZOBIA). RHIZOBIA LIVE IN ROOT NODULES AND FIX ATMOSPHERIC N INTO FORMS OF N THAT PLANTS CAN UTILIZE, AND IN RETURN, LEGUMES PROVIDE RHIZOBIA WITH SHELTER AND SUGARS PRODUCED DURING PHOTOSYNTHESIS. THIS SYMBIOSIS HAS POTENTIAL TO BE A USEFUL TOOL IN THE RESTORATION OF LLP SAVANNAS, AS RHIZOBIA FACILITATE THE RETURN OF BIOAVAILABLE N AFTER LOSSES FROM FIRE, THEREBY INCREASING UNDERSTORY PRODUCTIVITY AND ENSURING THE RETURN OF THE VEGETATION-FIRE FEEDBACK LOOP. BEFORE THIS SYMBIOSIS CAN BE USED AS A TOOL IN RESTORATION EFFORTS, WE MUST FIRST UNDERSTAND WHAT FACTORS INFLUENCE RATES OF N-FIXATION SO THAT WE CANMANIPULATE THESE FACTORS, ENHANCING N-FIXATION AND THE EFFICACY OF THE LEGUME-RHIZOBIA SYMBIOSIS. TO INVESTIGATE THIS, WEMEASURED SEVERAL ABIOTIC AND BIOTIC VARIABLES FOR 120 LEGUME INDIVIDUALS BELONGING TO FOUR SPECIES ACROSS 3 SITES FROM LONGLEAF PINE SAVANNA IN NORTH CAROLINA. WE THEN DUG UP THE PLANTS, REMOVED ROOT NODULES, AND INCUBATED THEM IN ACETYLENE GAS TO ESTIMATE N-FIXATION (RHIZOBIA USE THEIR NITROGENASE ENZYME TO CONVERT ACETYLENE TO ETHYLENE IN THE SAME WAY THEY CONVERT ATMOSPHERIC N INTO AMMONIA). USING THIS INFORMATION, WE ARE ABLE TO DETERMINE WHICH RHIZOBIA WERE RESPONSIBLE FOR THE GREATEST RATES OF N-FIXATION. IN A GREENHOUSE EXPERIMENT, WE WILL INOCULATE LEGUME SEEDS WITH EITHER THE RHIZOBIA THEY TYPICALLY ASSOCIATE WITH OR THE MOST EFFECTIVE N-FIXING RHIZOBIA, BOTHIDENTIFIED FROM OUR FIELD WORK. THIS GREENHOUSE EXPERIMENT WILL INFORM RESTORATION EFFORTS BY DETERMINING IF LEGUME SPECIES CAN ASSOCIATE WITH AN EFFECTIVE N-FIXING RHIZOBIA THAT THEY DON'T TYPICALLY FORM A SYMBIOSIS WITH, AND IF THIS LEADS TO INCREASES IN N-FIXATION, SOIL N, AND ABOVEGROUND PRODUCTIVITY COMPARED TO THE OTHER TREATMENT. OVERALL, THIS WORK WILL(1) FURTHER OUR UNDERSTANDING OF SYMBIOTIC N-FIXATION, (2) PUT PRACTICAL TOOLS IN THE HANDS OF RESTORATION PRACTITIONERS, AND (3) BRING BACK VALUABLE PRODUCTIVITY AND DIVERSITY LOST WITH THE DESTRUCTION OF THE ONCE WIDESPREAD LLP SAVANNA ECOSYSTEM.?