TRACE - Tree Rings in Archaeology, Climatology and Ecology

Abstract

According to the projections of the IPCC-scenario A1B, summer temperatures in southern Germany will increase up to 2.4°C until the end of this century. Even more important, a remarkable change in the seasonal distribution of precipitation is expected with an increase in winter precipitation and a decrease in summer rainfall. Summers are predicted to be warmer and drier while there will be a surplus of water in spring-time. Besides, extreme climate events in central Europe are expected to be more intense and more frequent. Thus, forests will most probably suffer from increasing and more frequent summer drought stress (Christensen et al. 2007 [IPCC], Rennenberg et al. 2004, Sutmoller et al. 2008). It is still uncertain how forests and individual tree species will react to these climatic changes and their consequences, but higher drought stress will probably influence the vitality, the stability and the productivity of European forests. As a result, forest management strategies as well as the choice of cultivated tree species have to be reconsidered and adjusted (Sutmoller et al. 2008). We study the growth reactions of common beech (Fagus sylvatica) and sessile oak (Quercus petraea (Mattuschka) Liebl.) to severe drought events. Climatic extreme events are often imprinted in tree rings as abrupt growth reductions which also influence tree growth of the years following a climatic extreme event (Schweingruber 2001). In the light of the expected increasing intensity and frequency of drought events in the future, it is important to know if beech and oak will still be able to grow on edaphically dry sites or if the recurrence interval between drought events will be too short for these species to recover. Our approach is therefore to determine the recreation time of beech and oak to recover from severe drought events during the 20 century. The final goal is to estimate if these tree species are already potentially endangered at dry sites or if they are able to cope with more frequent and intense drought events. Different wood parameters show diverse reactions and sensitivities to climatic variables (Skomarkova et al. 2006). Thus, we investigate a combination of the wood parameters ring width (RW), maximum latewood density (MXD), wood anatomical parameters and stable carbon isotopes. Here we focus on the reactions of ring width and MXD of Fagus sylvatica, which is one of the economically most important tree species in central Europe, to selected drought events.