Variability and influences of carbon exchange processes in German Forests

Tree growth and forest development depend to a large degree on climatic conditions. This is mostly because they are determining primary production, respiration losses, water demand and availability. The complex nature interacting climate components, however, represents a challenge if carbon sequestration and forest growth should be evaluated under changing conditions. Therefore, we apply a physiologically-based model (LandscapeDNDC) that has been evaluated on 15 ICOS flux tower sites, to all forested area in Germany in order to investigate the variability of carbon exchange processes in German Forests and their sensitivity to extreme events, specifically drought years. The results indicate that the net carbon sequestration is considerably reduced only in years and at sites with high water deficit (supply-demand) during extended periods of the growing period. The sensitivity to such stress, and thus also the variability between years, however, is different with species. Based on the simulations, we are also discussing the uncertainties related to model applications and the need to account for legacy effects.