Fra granplantefelt til stedegen fjellbjørkeskog i Junkerdalsura naturreservat: korttidseffekter av restaurering på vegetasjon

Abstract

In the forests of Europe, the planting of spruce in deciduous forests has had a significant impact on forest ecosystems. Junkerdalsura nature reserve north of Saltfjellet in Nordland has large areas covered by species rich mountain birch forests. A threat to these native birch forests is the spread of Norway spruce Picea abies, which was planted in parts of the reserve between the 1920s and 1960s. Restoration measures were therefore initiated to restore the native mountain birch forest with associated vegetation. Logging with timber extraction was carried out in two spruce plantations in 2018 and 2019. In 2022, we investigated the effect of these measures on the vegetation. We found that partial logging in an area with some remaining canopy cover of birch Betula pubescens and spring water influence, resulted in a species composition and cover of species in the field layer equivalent to the surrounding birch forest already three years after the restoration measure. More extensive logging in a somewhat drier area resulted in an increase of pioneer species mainly dominated by raspberry Rubus idaeus four years after the restoration measure. Although species richness did not reach the level of the birch forest in any of the areas, the results show that restoring species composition in birch forest can be fast if conditions are right. Logging intensity, remaining canopy cover and spring water influence can be important factors affecting the recovery process after restoration in boreal mountain birch forests. This study in Junkerdalsura is the only known study of restoration of boreal mountain birch forests in the Nordic countries and is an important contribution to the knowledge of restoration of these forests.