Effects of fuel treatments on basal area loss and soil burn severity in the Cedar Creek and Cub Creek 2 fires

Abstract

Fire regimes in the western United States have been significantly altered by the wildland fire suppression activities standard within 20th century land management practices. Well-intentioned fire suppression activities have increased tree stand density, fuel connectivity and loading, and the competitive stress placed on the forests. These changes, coupled with the forces of climate change have led to an increase in fire severity, the length of the fire-season, and the amount of area burned by fire. Modern hazardous fuel-reduction treatments such as thinning and prescribed burning can be used by land managers to reduce the frequency and extent of stand-replacement fires, with the goal of returning the fire regimes to their historical characteristics. Therefore, the aim of my study was to evaluate forested areas that have been damaged from large high severity fires to determine the impact, if any, that recent hazardous fuel reduction treatments had on post fire soil burn severity and basal area loss. In July 2021,the Cedar Creek fire and the Cub Creek 2 fire ignited in the dry-ponderosa pine forests surrounding the Methow Valley of Washington. Both fires were very large and burned through areas that had undergone fuel reduction treatments in the previous five years as well as areas that had not received fuel reduction treatments in that time period. The fire damage generated by these events provided the data for my study. I analyzed post fire soil burn severity and basal area loss using QGIS to create maps and calculate percentage area of fire effects for these variables. Treated areas were compared to similar untreated damaged areas, each classified by slope, aspect (north or south), and fuel type to aid in the analysis. Areas subject to fuel reduction treatments in both fires exhibited reduced proportions of high fire severity effects and greater proportions of low fire severity effects than did their comparison untreated areas. Consequently, with increases in fire severity and size, and the rising costs of fighting these fires, fuel reduction treatments can be used to reintroduce fire into the landscape at lower severity to improve forest resiliency.