2020

Hämäläinen, Karoliina; Junninen, Kaisa; Halme, Panu; Kouki, Jari

Successional and other temporal habitat changes may also affect conservation areas and reduce their conservation value. Active management to promote vulnerable habitat features may be an effective, but controversial, solution. Old deciduous trees and deciduous dead wood in boreal forest reserves are examples of habitat features that may be lost during succession, yet several threatened species, including the white-backed woodpecker (Dendrocopos leucotos), are dependent on them. Encroaching spruce have been removed from white-backed woodpecker territories to promote the regeneration of deciduous trees and to preserve habitat quality, although the efficiency of this treatment is unclear. In this study, we measured the canopy tree potential (integrating the number, height and condition) of aspen, birch and spruce saplings, and the number and basal area of mature trees in control and treatment sites 2–12 years after spruce removal. The canopy tree potential of aspen saplings increased on treated sites, along with a decrease in the number of spruce saplings and mature spruce trees. We found no evidence that spruce removal would benefit birch saplings. For both aspen and birch saplings, the abundance of mature trees of the same species increased their canopy tree potential more than spruce removal. Overall, our results indicate that spruce removal facilitates aspen regeneration, particularly in areas where large mature aspen trees are present. The lack of birch regeneration, however, indicates that maintaining a full array of important habitat characteristics in white-backed woodpecker territories may require a more comprehensive set of management tools than simply removal of spruce.