Forests under climate change: potential risks and opportunities

Climate change will affect forests in Germany through the end of this century. The impacts of climate change on forest productivity, water budget and the associated biotic and abiotic risks are relevant for the forestry sector and its decision makers. We analysed the possible impacts of climate change on Germany's forests using a variety of climate scenarios generated with the regional statistical climate model STARS and the process-based forest growth model 4C. The focus of our analyses was on mono-specific stands of the main tree species Norway spruce (Picea abies L. Karst.), Scots pine (Pinus sylvestris L.), European beech (Fagus sylvatica L.), oak (Quercus robur L. and Quercus petraea Liebl.), and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco). The impacts on net primary production of forest stands are mainly positive for needle tree species and more negative at low elevation, water-limited sites for broadleaved tree species like beech, which is in contrast to the overall tendency of deterioration of the annual percolation rates independent of tree species. The application of a fire danger index and a nun moth risk species index according to Zwlfer indicates that Germany's forests will experience, under the warmer and dryer climate described by RCP8.5, higher potential risks from fire and some specific pest species. An integrated evaluation reflecting the potentials and risks of forests under RCP8.5 for the German natural regions illustrates that the dryer (water-limited) low elevated regions reaching from southwestern to northeastern Germany will benefit less from the assumed climate change than regions in the Northwest and forest sites at higher altitudes, which are mainly temperature limited.