Fire history modulates burn severity in reburns, while daily fire weather and annual climate anomalies influence fire severity in all fires

Fire history modulates burn severity in reburns

Authors: Cansler, C. Alina, Kane, Van R., Kane, Jonathan T., Churchill, Derek J., Hessburg, Paul F., Lutz, James A., Povak, Nicholas A., Larson, Andrew J.

Abstract: We investigated the relative importance of fire weather, biophysical setting, and recent forest management and fire history to explaining patterns of remotely sensed fire severity in conifer forest in Northeastern Washington State, USA. Daily fire weather, annual precipitation anomalies, and the forest type—as measured by the fire resistance traits of the species—were important predictors of fire severity. In reburns, previous fire severity and time since the last fire influenced subsequent fires severity. Previous fires decrease severity of subsequent fires for up to 25 years. In areas managed before fire, thinning, harvest, and prescribed fire treatments had lower fire severity than matched untreated control areas, while recent plantings had higher fire severity. Prescribed fire was the most effective treatment at lowering subsequent fire severity. Prescribed fire areas were usually unburned or burned with low severity in subsequent fires. Management actions after a first fire only had weak influences on the severity of subsequent fires: harvest slightly increased fire severity, harvest combined with planting slightly decreased fire severity, and planting did not cause a clear directional change in subsequent fire severity. The importance of prescribed fire and past wildfire in moderating fire severity indicate the important role of forest management in reestablishing stabilizing fire-vegetation feedbacks using prescribed fire or managed wildfire with mechanical treatments.