Recent Climate Warming-Related Growth Decline Impairs European Beech in the Center of Its Distribution Range

Abstract

Increasing summer droughts represent a major threat for the vitality and productivity of forests in the temperate zone. European beech, the most important tree species of Central Europe’s natural forest vegetation, is known to suffer from increased drought intensity at its southern distribution limits, but it is not well known how this species is affected in the center of its distribution range in a sub-oceanic climate. We compared tree-ring chronologies and the climate sensitivity of growth (MS) in 11 mature beech stands along a precipitation gradient (855–576 mm y−1) on two soil types with contrasting water storage capacity (WSC) in northwest Germany to test the hypotheses that recent warming is impairing beech growth also in the center of its distribution below a certain precipitation limit, and stands with low soil WSC are more susceptible. We found a threshold of about 350 mm of mean growing season precipitation below which basal area increment (BAI) showed a consistent decline since the 1970s. The frequency of negative pointer years and MS were highest in low-precipitation stands on sandy soil, but both parameters have increased during the last decades also in the moister stands. The factor with largest impact on BAI was precipitation in June, in combination with high mid-summer temperatures. Contrary to our hypothesis, the edaphic effect on growth dynamics was surprisingly small. We conclude that global warming-related growth decline is affecting European beech even in the center of its distribution below a hydrological threshold that is mainly determined by mid-summer rainfall.