The Effects of Moose (Alces alces) Browsing on Boreal Tree Species in Norway and Quebec

The circumpolar boreal forest is important for recreational purposes, timber harvesting, game meat and as a CO2-storage. Biodiversity is important for maintaining these ecosystem services. Many boreal forests are experiencing an increase in the cervid populations. Densities of moose Alces alces not seen before in modern history have been reported several places. Knowledge about the interactions between this selective browser and the regenerating forest is therefore of importance for both the forest management in order to preserve biodiversity as well as for the forest industry. The aim of this paper is to study the impacts of moose browsing on tree height and density for early and late successional species in different boreal ecosystems. An experimental design with 51 exclosures and browsed controls in recent clear-cuts in Norway and Quebec (Canada) have been used to document the effects of browsing on a large regional scale. The deciduous species in both Canada (rowan Sorbus americana, birch Betula papyrifera) and Norway (rowan Sorbus aucuparia, birch Betula pubescens) showed an effect of the browsing treatment with a decreased height growth outside exclosures compared to inside exclosures. Balsam fir (Abies balsamea) was also affected by the treatment with a reduced height growth outside the exclosures. Spruce did not show an effect of the treatment in neither Norway (Picea abies) nor Quebec (Picea glauca). The effect of the treatment on the pine (Pinus sylvestris) in Norway was not statistically significant. This study has shown that although the ecosystem is not the same, species in the same successional stage show similar response to browsing. Since the boreal ecosystems around the world have different successional trajectories depending on their biological legacy and productivity, this knowledge is of importance when managing the forest and the cervid population