Future climate change impacts on forests in the Canton of Bern, Switzerland

Rapid anthropogenic climate change is projected to change forest composition and productivity in the coming decades to centuries. Forest managers and decision-makers therefore need regional-scale forest projections to assess climate change impacts and mitigate adverse effects by anticipatory forest management. Here, we simulate future forest composition in the Canton of Bern (Switzerland) under different climate and management scenarios, using the dynamic vegetation model LandClim. Our aim is to identify climate-change sensitive areas and tree species affected by increasing summer drought, in order to assess the potential of adaptive forest management to maintain current ecosystem services in today’s forests. Our results consistently show a decline of Picea abies under future climatic changes, either due to drought-induced mortality in lowland plantations or competitive replacement by temperate trees in its natural habitat. Our results also suggest that Fagus sylvatica can persist in favorable sites at low elevations, contradicting recent projections of a total disappearance on the Swiss Plateau. Additionally, our results support palaeoecological findings suggesting that Abies alba is well adapted to global warming conditions under low browsing intensity. Other trees that will thrive under higher temperatures and drier summers are Tilia cordata, Tilia platyphyllos, Ulmus glabra, Carpinus betulus, Quercus robur, Quercus petraea, Quercus pubescens and Acer pseudoplatanus. Warmer temperatures will also allow Mediterranean evergreen and deciduous species to establish first populations on the warmest and driest sites. Our results demonstrate that overall, Swiss forests might increase in biomass, suggesting that they can act as a net carbon sink. However, special attention must be given to southern exposed slopes and areas with shallow soils. There, climate change will have the most drastic and immediate effects with dieback of Fagus sylvatica and a shift to more drought-tolerant species.