Assessing the Impact of Climate Change Versus Land Use on Tree- and Forest Line Dynamics in Norway

Alpine tree- and forest lines (TFL) are dynamic, influenced by a variety of processes. In Norway, where TFLs are dominated by deciduous mountain birch, the lines are generally on the move to higher altitudes. Contemporary land use changes interfere the interpretation of the consequences of recent high latitude warming for TFL dynamics due to possible combined effects. We have assessed all available long-term studies (>30 years) (n = 8) of TFL dynamics focusing on separating the effects of climate change from those of changed land use in Norway. Most of the studies emphasize the importance of changed land use on TFL dynamics. However, a deeper understanding of the relevance of land use changes and climate changes for TLF dynamics and of possible interacting effects is hampered by a lack of spatially representative TFL change data and site-specific climate and land use change data.