Post-fire logging reduces surface woody fuels up to four decades following wildfire

Severe wildfires create pulses of dead trees that influence future fuel loads, fire behavior, and fire effects as they decay and deposit surface woody fuels. Harvesting fire-killed trees may reduce future surface woody fuels and related fire hazards, but the magnitude and timing of post-fire logging effects on woody fuels have not been fully assessed. To address this issue, we sampled surface woody fuels within 255 coniferous forest stands that burned with high fire severity in 68 wildfires between 1970 and 2007 in eastern Washington and Oregon, USA. Sampling included 96 stands that were logged after wildfire and 159 stands that were not logged. Most forest stands sampled were dominated by ponderosa pine (Pinus ponderosa) or Douglas-fir (Pseudotsuga menziesii) prior to wildfire and historically supported low and mixed-severity fire regimes. In unlogged stands, woody fuel loads were low initially, but then increased and peaked 10–20 years following wildfire. In logged stands, small and medium diameter woody fuel loads peaked immediately after logging, whereas large diameter woody fuel loads peaked 10–20 years after wildfire. Relative to unlogged stands, post-fire logging initially increased surface woody fuel loads, increasing small diameter fuel loads by up to 2.1 Mg/ha during the first 5 years after fire and increasing medium diameter fuel loads by up to 5.8 Mg/ha during the first 7 years after fire. Logging subsequently reduced surface woody fuel loads, reducing large diameter fuel loads by up to 53 Mg/ha between 6 and 39 years after wildfire, reducing medium diameter fuel loads by up to 2.4 Mg/ha between 12 and 23 years after wildfire, and reducing small diameter fuel loads by up to 1.4 Mg/ha between 10 and 28 years after wildfire. Logging also reduced rotten, large diameter fuel loads by up to 24 Mg/ha between 20 and 39 years after wildfire. Our study suggests that post-fire logging can significantly reduce future surface woody fuel levels in forests regenerating following wildfires. The magnitude of woody fuel reduction depends, however, on the volume and sizes of wood removed, logging methods, post-logging fuel treatments, and the amount of coarse woody debris left on-site to support wildlife habitat, erosion control, and other competing management objectives.