Regeneration Lags and Growth Trajectories Influence Passive Seismic Line Recovery in Western North American Boreal Forests

Across the western North American boreal region, networks of narrow clearings called seismic lines from oil and gas exploration fragment forests. Restoration of seismic lines for habitat recovery of threatened woodland caribou has been prioritized, but there is little guidance on temporal and spatial targets for boreal forest recovery. Between 2016 and 2022, we sampled regenerating trees on 344 seismic lines with limited re-disturbance across the oil sands region of Alberta, Canada. We modeled growth relationships for regenerating trees, including regeneration lags, using field and geospatial data to predict passive forest recovery on seismic lines. Recovery on seismic lines in peatland and transitional forests could take >30 years, due to longer regeneration lags (8–13 years) and slower-growing tree species (>25 years to reach 3 m). Recovery in xeric and mesic uplands was nearly half that, due to shorter regeneration lags (3–5 years), faster-growing species (9–13 years to reach 3 m), and recent wildfires. Over half of seismic lines in upland forests had predicted regeneration lags ≤5 years, including many seismic lines that burned after initial seismic line clearing, indicating regeneration was not delayed. However, all seismic lines in transitional and peatland forests were predicted to have regeneration lags >8 years. Slower recovery on seismic lines is associated with the compounding effects of longer regeneration lags and slower growth rates of dominant tree species. Restoration efforts should prioritize seismic lines where active treatment can significantly reduce regeneration lags and expedite growth.