Long-term effects of salvage logging after a catastrophic wind disturbance on forest structure in northern Japan

Many reports on the effects of conventional salvage logging—the removal of fallen and damaged trees after a catastrophic windthrow—on subsequent forest restoration have focused on short-term results occurring over less than 20 years; however, this time scale is inadequate, especially for boreal forests, because of the time required for tree growth. Here, we examine the long-term effects of salvage logging after a catastrophic windthrow event in 1954 on the resilience of a boreal forest by assessing the continuous recruitment of coniferous trees, dominance of typical coniferous tree species, and potential for future recruitment. We targeted two regions with different proportions of coniferous trees that were subject to three disturbance and management histories: windthrow (WT: fallen trees left intact), windthrow and salvage (WT+SL: salvage logged after the windthrow), and old growth (OG: not affected by the windthrow). In both regions, past salvaging has had serious negative impacts on the continuous recruitment of coniferous trees and potential for future recruitment. Negative impacts on the dominance of typical coniferous tree species were only observed in mixed forests. Our results suggest that in comparison to the coniferous forest, the mixed forest was less resilient, i.e.; the capability of a forest to maintain its identity as assessed by the dominance and recruitment of typical conifer species after wind disturbance and salvage logging. We found that salvage logging could affect forest structure, even 60 years later, by destroying advanced growth, including potential mother trees, and nursery beds for seedlings of typical conifer tree species.