**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** MANY WESTERN FORESTS ARE UNDER FREQUENT STRESS FROM DROUGHT, AND AT RISK FROM CATASTROPHIC WILDFIRES. WILDFIRES CAUSE IMMEDIATE LOSSES OF FOREST PRODUCTIVITY VIA MORTALITY AND STEM DAMAGE, BUT THE SEVERITY OF EFFECTS ON SOIL CAN ALSO COMPROMISE CRITICAL ECOSYSTEM SERVICES AND FOREST PRODUCTIVITY IN THE FUTURE BY DECREASING SOIL HEALTH, ESPECIALLY IN FORESTS THAT LACK ECOLOGICAL ADAPTION TO HIGH-SEVERITY BURNS. THIS PROJECT WILL PROVIDE FOUNDATIONAL KNOWLEDGE ABOUT HOW SOIL PROCESSES RESPOND TO FIRE, BY INVESTIGATING RELATIONSHIPS BETWEEN SOIL HEATING AND ITS DIRECT AND INDIRECT EFFECTS ON SOIL PROPERTIES THAT CONTRIBUTE TO SOIL HEALTH. THE OVER-ARCHING HYPOTHESIS IS THAT BURN SEVERITY AND SOIL HEATING DETERMINE THE MAGNITUDE OF IMPACT ON SOIL HEALTH, AS WELL AS ITS PATTERN, TIMEFRAME, AND LEVEL OF REBOUND. SPECIFICALLY, THIS PROJECT WILL (1) DEFINE RELATIONSHIPS BETWEEN SOIL BURN SEVERITY AND SOIL HEATING, AND (2) DETERMINE HOW SOIL PROPERTIES AND THE RESILIENCE OF SOIL HEALTH CHANGE AS A FUNCTION OF TEMPERATURE AND DURATION OF HEATING, AND ACROSS GRADIENTS OF SOIL BURN SEVERITY. WE WILL THEN (3) APPLY OUR DATA TO IMPROVE AND VALIDATE RESEARCH AND MANAGEMENT TOOLS, BY EXPANDING A NEW MODEL THAT PREDICTS BIOLOGICAL RESPONSE TO SOIL HEATING, VALIDATING MODEL PREDICTIONS IN WILDFIRE SITES. RESULTS WILL BE COMMUNICATED TO MANAGERS THROUGH A GUIDE RELATING PRE-FIRE SITE CHARACTERISTICS AND BURN SEVERITY TO RISKS TO SOIL HEALTH AND ASSOCIATED ECOSYSTEM SERVICES. IMPROVING SCIENTIFIC UNDERSTANDING OF THESE RELATIONSHIPS IS ESSENTIAL FOR MANAGING SOILS, WHICH ARE A NON-RENEWABLE RESOURCE AND THE FOUNDATION OF ECOSYSTEM PRODUCTIVITY.