Martin Gutsch

Projections of regional changes in forest net primary productivity for different tree species in Europe driven by climate change and carbon dioxide

Abstract• ContextProjecting changes in forest productivity in Europe is crucial for adapting forest management to changing environmental conditions.• AimsThe objective of this paper is to project forest productivity changes under different climate change scenarios at a large number of sites in Europe with a stand-scale process-based model.• MethodsWe applied the process-based forest growth model 4C at 132 typical forest sites of important European tree species in ten environmental zones using climate change scenarios from three different climate models and two different assumptions about CO2 effects on productivity.• ResultsThis paper shows that future forest productivity will be affected by climate change and that these effects depend strongly on the climate scenario used and the persistence of CO2 effects. We find that productivity increases in Northern Europe, increases or decreases in Central Europe, and decreases in Southern Europe. This geographical pattern is mirrored by the responses of the individual tree species. The productivity of Scots pine and Norway spruce, mostly located in central and northern Europe, increases while the productivity of Common beech and oak in southern regions decreases. It is important to note that we consider the physiological response to climate change excluding disturbances or management.• ConclusionsDifferent climate change scenarios and assumptions about the persistence of CO2 effects lead to uncertain projections of future forest productivity. These uncertainties need to be integrated into forest management planning and adaptation of forest management to climate change using adaptive management frameworks.

Mistletoe-induced growth reductions at the forest stand scale

The hemiparasite European mistletoe (Viscum album L.) adversely affects growth and reproduction of the host Scots pine (Pinus sylvestris L.) and in consequence may lead to tree death. Here, we aimed to estimate mistletoe-induced losses in timber yield applying the process-based forest growth model 4C. The parasite was implemented into the eco-physiological forest growth model 4C using (literature-derived) established impacts of the parasite on the trees water and carbon cycle. The amended model was validated simulating a sample forest stand in the Berlin area (Germany) comprising trees with and without mistletoe infection. At the same forest stand, tree core measurements were taken to evaluate simulated and observed growth. A subsample of trees were harvested to quantify biomass compartments of the tree canopy and to derive a growth function of the mistletoe population. The process-based simulations of the forest stand revealed 27% reduction in basal area increment (BAI) during the last 9 years of heavy infection, which was confirmed by the measurements (29% mean growth reduction). The long-term simulations of the forest stand before and during the parasite infection showed that the amended forest growth model 4C depicts well the BAI growth pattern during >100 years and also quantifies well the mistletoe-induced growth reductions in Scots pine stands.

Wald und Forstwirtschaft

In der Vergangenheit haben sich Walder an die geringen Veranderungen des am Wuchsort herrschenden Klimas angepasst. Die gegenwartige Geschwindigkeit des Klimawandels in Verbindung mit der aktuellen Verteilung der Baumarten uberfordert jedoch die naturliche Anpassung. Vegetationszonen, Verbreitungsgebiete der Baumarten und Artzusammensetzung der Walder verschieben sich. Das Kapitel charakterisiert die Folgen, die der Klimawandel fur die Walder mit sich bringt, stellt Schadfaktoren im Einzelnen vor und schildert die Auswirkungen auf die Produktivitat. Daruber hinaus wird detailliert auf die Rolle des Waldes als Kohlenstoffspeicher eingegangen, denn Walder produzieren nicht nur den nachwachsenden Rohstoff Holz, sondern sie leisten auch viel fur die Umwelt und wirken ausgleichend auf das Klima. Auch mogliche Anpassungsoptionen werden dargestellt.