Simon Emil Mutterer

Close-to-nature forestry (CNF) is considered an effective strategy to adapt forests to climate change while sustaining ecosystem services and biodiversity (BES). However, for forest management it remains unclear whether current CNF strategies sufficiently reduce forests' predisposition to climate-change-induced shifts in disturbance regimes. To address this increasing complexity, we introduce the integration of a climate-sensitive forest gap model with assessments of predisposition to fire, bark beetle, and windthrow disturbances, as well as BES provision. We conducted simulations for a forest enterprise in the Central Swiss Alps, covering a large elevation gradient, under three climate scenarios (historical, SSP2–4.5, and SSP5–8.5). The simulations additionally considered six management strategies, including CNF variants with different management intensities and climate-adapted approaches. Our results indicate that climate change will dynamically alter disturbance predisposition across elevation gradients. Site-related predisposition to fire and bark beetle infestation generally increased under climate change, while stand-related predisposition to all disturbances varied with climate scenario and elevation. Under moderate warming (SSP2–4.5), stand-related predisposition to fire and windthrow increased across all elevations. In contrast, under severe warming (SSP5–8.5), long-term reductions in stand-related predisposition to fire, bark beetle infestation, and windthrow occurred at lower elevations due to climate-change-induced shifts in forest dynamics, while predisposition increased at higher elevations with improved growing conditions. Our results further show that increasing management intensity generally reduces stand-related disturbance predisposition but focusing purely on disturbance mitigation can also lead to trade-offs, such as reduced BES provision. We conclude that climate-adapted forest management must account for both stand-related and site-related predisposition to prioritize disturbance-prone 'hotspots', especially in areas of high BES value. Proactively reducing disturbance predisposition may involve trade-offs regarding BES provision but may be crucial to avoid potential BES losses from severe disturbances. As climate change may alter trade-offs between BES and disturbance mitigation, we underscore the need for decision support systems in long-term forest planning to account for conflicting management objectives.

Strategic long-term planning of mountain forests in the European Alps requires a balancing act between sustaining forest biodiversity and ecosystem services (BES) and mitigating disturbance risks, particularly under climate change. Multi-criteria decision support systems (DSSs) address this challenge by integrating climate-sensitive forest modelling into frameworks for the evaluation of BES provision under simulated climate and management trajectories. Recent developments incorporate assessments of disturbance predisposition into DSSs, accounting for risks from bark beetle infestations and windthrow. These DSS frameworks have proven flexible applicability across various forest models, spatial scales, forest types, and environmental conditions. However, climate-change-induced transitions of disturbance regimes require adaptations of existing DSS frameworks by accounting for emerging disturbance agents, such as forest fires. Here, we introduce the integration of a fire predisposition assessment system (PAS) into a DSS, incorporating factors such as topography, climatic conditions, wildland–urban interface, and stand structural characteristics. Particularly in the context of long-term planning in mountain forests, the expanded DSS could enable the identification of conflicting forest management objectives related to BES provision and disturbance mitigation efforts under climate change, leading to more informed management decisions.

• A predisposition assessment system for assessing multiple predisposing factors of forest fires is presented.
• The fire PAS enables an integrated evaluation with disturbance predisposition to bark beetle infestations and windthrow, as well as BES provision.
• The modular structure of the fire PAS enables adaptation and application to various spatial scales, as well as integration with different forest models.

Close-to-nature forestry (CNF) has a long tradition in European Alpine forest management, playing a crucial role in ensuring the continuous provision of biodiversity and forest ecosystem services, including protection against natural hazards. However, climate change is causing huge uncertainties about the future applicability of CNF in the Alpine region. The question arises as to whether current CNF practices are still suitable for adapting forests to climate change impacts while also meeting the increasing societal demands regarding Alpine forests, including their potential contribution to climate change mitigation. To answer this question, we simulated forest development using the ForClim forest model at two Alpine study sites, together representing a large biogeographic gradient from high-elevation inner Alpine forests (Switzerland) to lower-elevation south-eastern Alpine forests (Slovenia). The simulations considered three climate scenarios (historical climate, SSP2-4.5 and SSP5-8.5) and six alternative management strategies, including both current CNF management practices and climate-adapted versions. Using an indicator based multi-criteria decision analysis framework, we assessed the joint impacts of climate and management on biodiversity and key ecosystem services of the investigated regions, including carbon sequestration (CS) inside and outside the forest ecosystem boundary. The joint effects of climate change and CNF varied, both among and within the study sites along the biogeographical gradient. While CS was more resistant to climate change under current CNF at the south-eastern Alpine site, it was more sensitive at the inner Alpine site, where CS potentials decreased at lower elevations. This adverse effect could be partly mitigated by fostering the use of climate-adapted tree species. However, current CNF and adaptations of it did not meet multiple management objectives equally well: while protection from gravitation hazards and timber production also benefited from this silvicultural practice, biodiversity benefited from CNF variants with low-intensity or no management. In conclusion, CNF has a high potential to continue fulfilling its crucial role in European Alpine forests. A differentiated approach will be needed in the future, however, to identify forest stands where adaptive measures are required, especially at sites particularly vulnerable to climate change. In combination with less intensively managed or unmanaged areas, CNF provides a management portfolio that will help European Alpine forests to meet the demands of future society.