Veteran trees and deadwood are key elements to maintain forest biodiversity. Setting aside protected forest areas and old-growth patches is a recent concept intended to favor deadwood dependent species. We compared forest areas where no harvesting occurred for at least 30 years with regularly managed forests, in order to assess the efficiency of such conservation measures. We collected data from 24 sites in Switzerland, where we inventoried dead trees and habitat structures such as cavities, cracks, bark pockets, etc.

In unmanaged forests we found deadwood amounts of 98–143 m3 and 20 snags > 30 cm DBH per hectare, one and half time more large trees (> 60 cm DBH) und twice as many habitat structures as in managed forests. The latter had in average 15–19 m3 of deadwood and 3 snags > 30 cm DBH per hectare. Deadwood amounts in unmanaged forests were similar to the ones in natural forests of central Europe. However, we found 10–50 times less veteran trees (> 80 cm DBH) than in natural forests (1 vs. 0.2 trees per hectare in unmanaged vs. managed forests). For equal diameter classes, trees had more habitat structures in unmanaged than in managed forests. Forest managers plan to intensify wood harvesting in Swiss forests. Consequently, we recommend to urgently set aside protected forest areas and old-growth patches, to maintain and favor habitat trees in managed forests, and to introduce an efficient sustainable deadwood management in any forest.

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