UNDERSTANDING THE FACTORS THAT DRIVE RANGELAND ECOSYSTEM RESPONSES TO LAND MANAGEMENT WILL ALLOW LAND MANAGERS TO BETTER ASSESS THEIR GOALS AND STRATEGIES. GRASSLANDS - IN PARTICULAR, GRAZED RANGELANDS - SUPPORT MORE THAN 1 BILLION PEOPLE ECONOMICALLY. IN CALIFORNIA ALONE, THE CATTLE INDUSTRY IS WORTH OVER $1 BILLION USD. THESE MESIC AND SEMI-ARID ECOSYSTEMS ARE PARTICULARLY VULNERABLE TO SHIFTING DROUGHT REGIMES WHERE MANAGING FOR CONSISTENT FORAGE IS A CONSTANT A CHALLENGE FOR RANGELAND MANAGERS DUE TO INCREASINGLY HIGH RAINFALL VARIABILITY AND FREQUENT DROUGHTS. WITH GROWING POPULATION DEMANDS AND THE VARIABLE CONDITIONS CAUSED BY CLIMATE CHANGE, MAINTAINING AND IMPROVING THE FUNCTIONING OF EXISTING RANGELANDS IS ESSENTIAL FOR LONG-TERM SUSTAINABILITY, THE ECONOMIC VIABILITY OF RANCHING, AND ENHANCING THE QUALITY OF LIFE FOR RANCHERS. WHILEFORAGE PRODUCTION HAS BEEN THE TRADITIONAL ECONOMIC MOTIVATION ON RANGELANDS, THERE IS GROWING INTEREST IN ACTIVELY MANAGING RANGELANDS FOR BELOWGROUND ECOSYSTEM FUNCTIONS, SUCH AS SOIL C STORAGE AS A MITIGATION STRATEGY FOR CLIMATE CHANGE. RANGELAND MANAGERS FACE INCREASING CHALLENGES FROM CLIMATE CHANGE WHERE MORE VARIABLE PRECIPITATION AND DROUGHT CHANGE WATER AND NUTRIENT DYNAMICS ACROSS LANDSCAPES. CHANGES TO RESOURCE AVAILABILITY UNDER DIFFERENT LAND MANAGEMENT STRATEGIES (E.G., WATER AND NUTRIENTS) ARE LINKED TO ECOSYSTEM FUNCTION, BUT MECHANISMS ARE POORLY UNDERSTOOD, ESPECIALLY FOR BELOWGROUND FUNCTIONS. WHILE ABOVEGROUND PLANT PRODUCTIVITY IS WELL-STUDIED, BELOWGROUND RESPONSES TO LAND MANAGEMENT ARE RELATIVELY UNKNOWN.THE PREMISE OF MY PROPOSAL IS THAT SOIL BIOLOGICAL COMMUNITIES ARE OVERLOOKED DRIVERS, AND THEIR INTERACTIONS WITH PLANTSEXPLAIN AND PREDICT BELOWGROUND RESPONSES IN A HEURISTIC WAY.MY PROJECT TESTS MECHANISMS OF BELOWGROUND CONTROLS ON RANGELAND ECOSYSTEM FUNCTIONING AND IDENTIFIESPLANT TRAITS USEFUL FOR PREDICTING BELOWGROUND RESPONSE TO MANAGEMENT IN A SIMPLE FRAMEWORK. THIS PREDICTIVE FRAMEWORK CAN BE APPLIED EASILY TO OTHER LAND MANAGEMENT STRATEGIES AS A HEURISTIC TOOL. TAKING A SOIL ECOLOGY APPROACH, MY RESEARCH INCLUDES: 1) A SOIL COMMUNITY SURVEY WITHIN A COMPOST AMENDMENT EXPERIMENT, AND 2) A SOIL COMMUNITY EXPERIMENT PAIRED WITH A PLANT TRAIT STUDY TO IMPROVE PREDICTABILITY OF RANGELAND ECOSYSTEM FUNCTION IN RESPONSE TO LAND MANAGEMENT PRACTICES. IN THE SURVEY, I WILL COLLECT SOIL SAMPLES TO ASSESS BELOWGROUND ROOT PRODUCTION, THEIR ARBUSCULAR MYCORRHIZAL FUNGI, AND SOIL NEMATODE ABUNDANCE ACROSS AN ESTABLISHED EXPERIMENT, WHERE THREE AMENDMENT TREATMENTS (COMPOST, INORGANIC NITROGENFERTILIZER, AND NO AMENDMENT) ARE CROSSED WITH THREE PRECIPITATION TREATMENTS (DRY, WET, AND AMBIENT). FOR THE SOIL COMMUNITY EXPERIMENT, I WILL PLANT THREE SPECIES THAT REPRESENT MAJOR FUNCTIONAL GROUPS (E.G. GRASSES, LEGUMES, AND FORBS) AT COMPOSITION RATES TARGETED BY MANAGERS WITHIN THE ESTABLISHED EXPERIMENT. WITHIN THESE SEEDED PLOTS, I WILL ESTABLISH FOUR SOIL COMMUNITY MANIPULATIONS:CONTROL COMMUNITY, NO FUNGI, NO NEMATODES, AND NO FUNGI OR NEMATODES AND WILL ASSESS FUNGI, NEMATODES, AND PLANT TRAITRESPONSES. THIS PROJECT ADDRESSES AFRI FARM BILL PRIORITY AREA 4 - BIOENERGY, NATURAL RESOURCES, AND ENVIRONMENT, BY SPECIFICALLY ADDRESSING SUSTAINABILITY GOALS TO IMPROVE ENVIRONMENTAL QUALITY AND THE NATURAL RESOURCES UPON WHICH AGRICULTURE DEPENDS BY IMPROVING LAND MANAGEMENT EFFICIENCY THROUGH BETTER UNDERSTANDING OF NATURAL BIOLOGICAL FEEDBACKS. THE OVERALL GOAL OF MY PROPOSED RESEARCH IS TO TEST PLANT AND SOIL RESPONSES TO LAND MANAGEMENT TO GENERATE A PREDICTIVE FRAMEWORK FOR BELOWGROUND ECOSYSTEM FUNCTIONS WITH THE AIM OFIMPROVINGPLANT PRODUCTIVITY ON RANGELANDS AND PROVIDING GUIDANCE FORMANAGEMENT DECISIONS BASED ON SPECIFIC GOALS, SUCH AS GREATER FORAGE OR SOIL C STORAGE.IN ADDITION TO RESEARCH SUPPORT, THE USDA NIFA POSTDOCTORAL FELLOWSHIP WILL PROVIDE CRITICAL SKILLS AND EXPERIENCE THROUGH PROFESSIONAL CAREER DEVELOPMENT TO CULTIVATE MY SUCCESS AS AN INDEPENDENT RESEARCHER AND LEADER IN AGROECOLOGY