A comprehensive study on forest management and wildfire trends in dry western coniferous regions of the United States

Abstract

In response to the growing concern over the escalating severity of wildfires in dry coniferous forests across the Western United States, this study aims to evaluate the effectiveness of Managed Fire Operations (MFO) in mitigating wildfire severity. By leveraging satellite-derived fire severity data, specifically the Difference Normalized Burn Ratio (dNBR), I conducted a comprehensive analysis comparing fire severity between forest lands with and without MFO, subsequently affected by wildfires. Employing a paired study design, I analyzed wildfire events from 1985 to 2021 within dry coniferous forests, limited to south-facing slopes with moderate terrain gradients, using fire perimeter data from the Monitoring Trends in Burn Severity (MTBS) program. Geospatial analysis identified areas where wildfire perimeters intersected with MFO-designated zones, enabling the delineation of new burn perimeters for each wildfire. The results revealed that regions subjected to MFO before wildfires experienced a statistically significant decrease in fire severity compared to areas without MFO (Wilcoxon signed-rank test, p-value < .01). Ecoregion stratification revealed notable variations, with the Northwestern Forested Mountains showing an estimated median fire severity difference nearly three times greater than the Temperate Sierras. Further stratification by time since MFO implementation displayed consistent, modest reductions in fire severity across two intervals (0-15 years and 15-40 years), with minimal variations between the temporal categories. These results highlight the effectiveness of MFO in mitigating wildfire severity and emphasize the importance of regional context and temporal factors in evaluating MFO efficacy in Western U.S. dry coniferous forests over the past four decades.