Borkenkäferdynamik im klimawandel: Die bedeutung der landschaftsebene

Climate change affects forest development directly through rising temperatures and changing precipitation patterns and indirectly through changes in the disturbance regime. Bark beetles are a key factor in the future development of forests dominated by spruce (Picea abies), but the manifold interactions between forest stand, bark beetles and weather and climate are difficult to analyse. To quantify these influences, forest landscape models such as LandClim have been developed. These models typically combine processes of local forest development (growth, mortality, regeneration) with those tak-ing place at landscape level (seed dispersal, forest manage-ment, disturbances). This article uses the example of LandClim to show how forest landscape models are structured and how they can be applied to model future forest development at the landscape level. In a case study in the Dischma valley near Davos (canton of Grisons, Switzerland) we investigated the dynamics of disturbances by the European spruce bark beetle (Ips typographus) under past climate and under a climate change scenario with two windthrow scenarios. The simulations showed a marked increase in beetle-induced spruce mortality under climate change and an amplifying effect of windthrow on beetle damage, which only occurred under climate change but not under the past climate. We discuss the broad application of LandClim, which ranges from climate-adaptive management to disturbance ecology and palaeoeco-logy, and the disadvantages resulting from the general model structure. LandClim is best suited to understand the relative importance of climate, disturbance and management effects, but less suited for precise predictions of timber supply, stem numbers or harvesting potential.