Climate change impacts across a large forest enterprise in the Northern Pre-Alps: dynamic forest modelling as a tool for decision support

Mountain forest managers face the challenge to anticipate climate change (CC) impacts across large elevational ranges. For management planning, information on site-specific long-term responses to CC as well as the consequences for protection functions is particularly crucial. We used the process-based model ForClim to provide projections of forest development and their protective function as decision support for a large forest enterprise in the Northern Pre-Alps. Specifically, we investigated the impact of three climate scenarios (present climate, low- and high-impact CC) at five representative sites along an elevational gradient (700–1450 m a.s.l.). Relatively small changes to current forest structure and composition were evident under present climate, but divergent trajectories occurred under CC: while the low-elevation sites (≤ 1000 m) were affected by drought-related mortality, high-elevation sites benefited from the warming. Changes at low-elevation sites were accompanied by shifts in species composition, favouring in particular Tilia (‘low-impact’ CC) and Pinus sylvestris (‘high-impact’ CC). Forest management accelerated the shift towards climate-adapted tree species, thereby reducing detrimental effects of the ‘low-impact’ CC scenario. Under the ‘high-impact’ scenario, however, drastic decreases in protective function occurred for the late twenty-first century at low elevations. A set of exemplary disturbance scenarios (windthrow and bark beetle) demonstrated the importance of forest management and low browsing for the resilience of mountain forests. Overall, our results underline the potential of process-based forest models as decision support tools for forest enterprises, providing local projections of CC impacts across large elevational ranges at the site-specific resolution required by forest managers.