Wildfire-initiated dead wood legacies: Post-fire habitat and fuels trajectories in westside Pacific Northwest forests, USA

Managers grappling with questions about dead wood in productive, often high-volume, westside Pacific Northwest forests seek to balance wildlife habitat quality and fire hazard reduction, especially following wildfires which can both consume and generate exceptional quantities of dead wood. Longitudinal analysis of a large (n = 327) sample of permanent forest inventory monitoring plots measured before and repeatedly after wildfires and an equal-sized sample of comparable but unburned reference plots revealed post-fire trajectories of dead wood and factors that drive abundance of snags, litter, duff, fine (FW) and coarse down wood (CW) over the first two decades post-fire. Fire generated pulses of snag recruitment in these forests, increasing snag density to an average of 3X that found on unburned reference plots, and 5X where fire burned at high severity. Depending on fire severity, 25–45 % of these snags fell within the first two decades after fire, producing a lagged pulse of new down wood that yielded CW stocks 1.5X those found on unburned reference plots. Fine fuel loads were reduced in burned stands initially post-fire, but FW and litter began to re-accumulate during the first post-fire decade, returning to levels seen on unburned reference plots. Thus fire-initiated reductions in reburn potential were temporary while increases in proportion of forested landscape with the elevated levels of dead wood needed to support high quality wildlife habitat persisted.