Persistent impact of conventional seismic lines on boreal vegetation structure following wildfire

Linear disturbances from geological exploration (i.e., seismic lines) have an extensive footprint across much of Canada’s western boreal forest; however, how seismic lines interact with subsequent wildfire remains poorly understood. We assessed whether wildfires effectively mitigate the footprint of seismic lines by promoting forest recovery. We evaluated the forest structure of legacy seismic lines burned in 2001 and 2002 by comparing them against adjacent unburned control plots, using metrics derived from airborne laser scanning (ALS) data collected between 2007 and 2009. Airborne laser scanning metrics identified persistent differences in vegetation height and structure between seismic lines and adjacent forest controls, seven to nine years post-fire. Median canopy height was 2.90 m lower on upland seismic lines and 1.94 m lower on lowland seismic lines than on adjacent controls, corresponding to a 21% and 25% height reduction, respectively. Field surveys revealed greater graminoid and non-vascular plant cover, and lower tall-tree cover and dead vegetative matter, on seismic lines, in comparison with controls. Our results show that tree recovery remains significantly delayed on most upland and lowland burned seismic lines in our study area, and that additional management efforts or longer timescales may be required to restore these fragmented landscapes.