Are key ecological attributes maintained following the establishment cut in an irregular shelterwood system?

The persistence of ecological attributes associated with late-successional forests has rarely been studied in the context of the irregular shelterwood system. This study assesses the abundance of legacy trees (cavity or potential cavity trees, fruit trees or veteran trees, live and dead), standing dead trees and coarse woody debris in six forest types in Québec (Canada) using 37 blocks of paired natural stands treated with operational irregular shelterwood or left as unmanaged controls. Treated stands retained a lower abundance than unmanaged control for legacy trees (70 ± 7 vs. 32 ± 4 trees·ha−1), standing dead trees (145 ± 13 vs. 81 ± 8 trees·ha−1) and coarse woody debris (26 ± 3 vs. 16 ± 2 m³·ha−1), representing respectively decreases of 54, 44 and 38%. Despite these reductions, post-harvest averages generally exceeded current retention thresholds. Irregular shelterwood can help maintain key late-successional structural attributes after the establishment cut, but retention measures are recommended when pre-harvest abundances are low.