High severity wildfires produce pulses of dead trees (snags) and initiate fuel succession processes in which snags decompose and deposit fuels on the forest floor while forest vegetation recovers and produces litter and progressively larger surface fuels. These pulses of fuel succession are important for future fire behavior in dry coniferous forests where wildfires are likely to recur before wood decay processes are complete. The decay status of large woody fuels can also influence fire behavior and effects, as rotten logs may burn more thoroughly than sound logs. Post-fire logging has been proposed for reducing future fuels economically, but the practice remains controversial. By removing large amounts of woody biomass, post-fire logging clearly reduces total potential fuels, but also accelerates the snag decomposition process. The purpose of this study was to compare patterns and rates of fuel succession after wildfire, with and without post-fire logging. To do this, we sampled fire-killed trees and surface fuels on 255 plots across a chronosequence of 49 wildfires that burned dry coniferous forests of eastern Washington and Oregon during 1970-2007. 

Results/Conclusions

Without logging, surface accumulations of small diameter fuels (up to 7.6 cm) and larger diameter (> 7.6 cm) sound fuels increased to a maximum 10-20 years following fire and then declined, with large diameter fuels peaking later than small diameter fuels.  Large diameter rotten fuels increased monotonically with time since fire, and pre-fire stand basal area was positively correlated with loadings of large diameter fuels.  Small diameter surface fuel loads were higher on logged sites than on unlogged sites shortly after fire and logging. However, small diameter surface fuels on unlogged sites exceeded those on logged sites from 5-10 years following wildfire through at least 30 years after fire. Large diameter woody fuels were higher on logged than on unlogged sites during the first 3-5 years following wildfire, but thereafter were lower on logged sites through at least 35 years after wildfire. Our study suggests that post-fire logging increases potential fire intensity during the first 5-10 years following wildfire, particularly if logging slash is left untreated and there is sufficient horizontal connectivity in fine fuels to facilitate fire spread. Thereafter, logging reduces potential fire intensity and severity (particularly for soils) by reducing both small and large diameter fuels and the amount of rotten large wood.