Climate Warming-Related Growth Decline Affects Fagus sylvatica, But Not Other Broad-Leaved Tree Species in Central European Mixed Forests

Climate warming is predicted to extend the duration and enhance the severity of summer droughts in Central Europe, which may pose a serious risk to forest productivity and forest health. Fagus sylvatica (European beech), the most abundant tree species of Central Europe's natural forest vegetation and one of the key species in forestry, is thought to be particularly vulnerable to drought. Here, we present a dendrochronological analysis in three mixed temperate broad-leaved forests along a precipitation gradient with the aim of comparing the climatic response of radial growth of F. sylvatica with the performance of four co-existing species (Acer pseudoplatanus, A. platanoides, Quercus petraea, Fraxinus excelsior). We hypothesized that Fagus is the most drought sensitive of the five species, which implies that it could lose its competitive advantage at drier sites in the course of climate warming. In support of this hypothesis, we found that F. sylvatica in all stands exhibited an increase in the number of negative pointer years and a decrease in radial increment in the driest stand since about 1980, in parallel to increasing summer temperatures and drought intensity. Such a response was missing in the other four species and may point to shifts in the competitive hierarchy in these mixed forests under a future warmer climate. We conclude that Central Europe's forestry sector should consider carefully the risk of failure of beech in regions with relatively low and decreasing summer precipitation.