The influence of climate and management on survival probability for Germany's most important tree species

Due to climate change for many regions an increase in tree mortality is expected. Considering changes in mortality risk is important for management decisions. Therefore, models are needed that predict mortality risk under future climate. We fitted survival models for Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), Silver Fir (Abies alba Mill.), Douglas fir (Pseudotsuga menziesii (Mirbel) Franco), European beech (Fagus sylvatica L.), sessile oak (Quercus petraea (Mattuschka) Liebl.), and pedunculate oak (Quercus robur L.) based on the German crown condition survey as well as pan-European crown condition data from Level I and Level II plots, thus encompassing large environmental gradients. We used parametric accelerated failure time models assuming Weibull- or log-normal distribution of survival times. The models allow to estimate survival probability in dependence on age, climate and species mixture. For all species, a decrease in survival probability with increasing temperatures was found. Decreasing precipitation increased mortality risk for Norway spruce, Scots pine and Douglas fir. In addition, for Norway spruce and Douglas fir a positive effect of species admixture on survival was found. In summary, we could fit parsimonious parametric survival models explaining differences in survival times by 30-year climate averages that we interpret as predisposing factors that increase a tree's vulnerability. However, uncertainty in estimations remains high due to limitations of the sampling design and the methodology.