Drought Stress Reaction of Growth and Δ13C in Tree Rings of European Beech and Norway Spruce in Monospecific Versus Mixed Stands Along a Precipitation Gradient

Tree rings include retrospective information about the relationship between climate and growth, making it possible to predict growth reaction under changing climate. Previous studies examined species-specific reactions under different environmental conditions from the perspective of tree ring growth and 13C discrimination (Δ13C). This approach is extended to monospecific versus mixed stands in the present paper. We investigated the resistance and resilience of Norway spruce (Picea abies [L.] Karst) and European beech (Fagus sylvatica [L.]) in response to the drought event in 2003. The study was carried out along a precipitation gradient in southern Germany. Responses of basal area increment (BAI) and Δ13C were correlated with a Climate-Vegetation-Productivity-Index (CVPI). The species showed different strategies for coping with drought stress. During the summer drought of 2003, the BAI of spruces reveal a lower resistance to drought on dry sites than those of beech. For beech, we found an increasing resistance in BAI and Δ13C from dry to moist sites. In mixture with spruce, beech had higher resistance and resilience for Δ13C with increasing site moisture. The combination of Δ13C and tree ring growth proxies improves our knowledge of species-specific and mixture-specific reactions to drought for sites with different moisture conditions