FORESTED RIPARIAN BUFFERS ARE A CENTRAL STRATEGY FOR SUSTAINABLE AGRICULTURAL INTENSIFICATION. TREE ROOTS IN AGRICULTURAL MARGINS INTERCEPT LEACHED NUTRIENTS, SUCH AS NITROGEN (N), TO MEET WATER QUALITY GOALS. HOWEVER, THESE BUFFERS CAN BECOME HOTSPOTS FOR "POLLUTION SWAPPING"-- DECREASING N IN STREAMS BUT EMITTING N2O, A GREENHOUSE GAS WITH 300X THE WARMING POTENTIAL OF CO2. THERE IS A PRESSING NEED TO DESIGN BUFFERS THAT BALANCE THESE WATER QUALITY AND CLIMATE CHANGE OBJECTIVES.I PROPOSE TWO FIELD AND ONE GREENHOUSE EXPERIMENTS TO EXPLORE CONTROLS ON N POLLUTION SWAPPING OVER THE LIFE OF AN EDGE-OF-FIELD RIPARIAN BUFFER, AND TO TEST THE POTENTIAL FOR INTENTIONALLY SELECTING TREE SPECIES THAT OPTIMIZE N RETENTION. SPECIFICALLY, I WILL (1) ESTIMATE N POLLUTION SWAPPING FROM EDGE-OF-FIELD BUFFERS ACROSS TIME; (2) EXPLORE HOW TREE PHYSIOLOGY MODIFIES N2O EMISSIONS FROM BUFFERS; AND (3) LINK SPECIES' ROOT PHYSIOLOGY TO RELATIVE N2O:N2 EMISSIONS. LEVERAGING A BUFFER AGE GRADIENT, I WILL ACHIEVE MY OBJECTIVES THROUGH COLLOCATED MANUAL CHAMBERS, ROOT IN-GROWTH CORES, AND DENITRIFICATION POTENTIAL IN THE FIELD, AND THROUGH AN ISOTOPE TRACER STUDY IN SOIL COLUMNS.GLOBALLY, RIPARIAN AREAS ARE A SIGNIFICANT SOURCE OF N2O, AND MY WORK QUANTIFIES THESE EMISSIONS AS BUFFERS AGE (OBJECTIVE 1). WITH INSIGHT INTO MECHANISMS THAT PARTITION DENITRIFICATION INTO N2O AND N2 (OBJECTIVES 2 &AMP; 3), WE CAN DESIGN SUSTAINABLE BUFFERS THAT USE PLANTS TO DRIVE COMPLETE DENITRIFICATION IN SUPPORT OF THE FARM BILL PRIORITY AREA 4 AND NIFA STRATEGIC SUB-GOAL 1.3. MY RESEARCH AND PROFESSIONAL DEVELOPMENT OBJECTIVES ALIGN WITH THE AFRI-EWD GOAL OF ADVANCING SCIENCE.