Growth reaction of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus silvatica L.) to possible climatic changes in Germany.: A sensitivity study

The paper presents scenario calculations for the growth of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus silvatica L.) under climate change. Simulation runs with the individual tree model SILVA 2.2 show that the present increment increase in German forests under strong climate change may lead to severe increment reductions and shifts in competition between tree species. The current observed growth trends as well as the simulation results confirm that the reactions of Norway spruce stands to climatic changes vary widely. In addition, the reaction of Spruce and Beech may be quite different. The recent temperature increase as shown for the northern hemisphere and the prolongation of the vegetation period provides a probable explanation for the increment increase over large regions. The extent of the increment reaction depends on the species specific ecological amplitude and is superimposed by locally and regionally influences, such as soil characteristics, element inputs and biotic stressors. This superimposition generates a number of increment reaction patterns including positive and negative deviations from an expected development of an age typical increment. It delivers an explanation for the seemingly paradoxical result that even hypertrophic growth, increment reductions and death of stands can occur concurrently.