Wildfire Severity and Post-Fire Treefall Dynamics: Insights from Long-Term Trail Crew Records in the Absaroka Beartooth Wilderness

Abstract

Wildfire severity and frequency are increasing across the Northern Rockies, reshaping forest structure and management needs in wilderness landscapes. When fires cause extensive tree mortality, treefall can obstruct trail systems for years, creating sustained maintenance challenges where the use of mechanized tools is prohibited. Therefore, in this study I use long-term U.S. Forest Service trail crew records from the Absaroka-Beartooth Wilderness in Montana to quantify post-fire treefall dynamics and evaluate their relationship to burn severity, vegetation type and density, and topographic setting. Trail logs from three study areas serve as the basis for analysis: the Anderson Ridge Trail (Wicked Creek Fire, 2007), the Wallace Pass and Passage Creek Trails (Passage Falls and Wicked Creek Fires, 2006 and 2007), and the South Fork Deep Creek Trail (Pine Creek Fire, 2012). I standardize these records for trail length and maintenance interval to produce annualized treefall rates. I then integrate these data with spatial summaries from the Monitoring Trends in Burn Severity (MTBS) project, Landsat-derived Normalized Difference Vegetation Index (NDVI), LANDFIRE Existing Vegetation Type (EVT), and U.S. Geological Survey digital elevation models (DEM). Treefall rates increase sharply following fire across all study areas, with sustained onsets detected within five to seven years after fire and peaks occurring ten to thirteen years after fire. Across these sites, the timing and magnitude of post-fire increases generally track burn severity and canopy loss, while topographic factors show limited influence. High-severity burns with large NDVI declines tend to experience faster and more concentrated treefall, whereas mixed-severity burns exhibit slower, more prolonged responses. These results suggest that trail-crew records can capture meaningful patterns of post-fire snag fall and forest change in remote wilderness areas. By linking operational maintenance data with satellite-derived fire and vegetation metrics, this study demonstrates a transferable approach for anticipating long-term trail-clearing needs and informing wilderness management after fire.