Climate change in the forests of northern Germany

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Typical beech forest in northern Germany: the scientists took wood cores from doTypical beech forest in northern Germany: the scientists took wood cores from dominant trees at a total of 30 sites. Photo: Banzragch Bat-Enerel
Research team from the University of Göttingen demonstrates widespread drought stress in copper beech

More and more trees are suffering the consequences of the man-made climate change of recent decades. The growth of the copper beech - mainly at home in Central Europe and Germany’s most important native forest tree species - has so far declined mainly in southern Europe. A research team from the University of Göttingen has now been able to show that the copper beech also suffers from increasing drought stress in summer in northern Germany. This climatic stress was particularly pronounced at warmer sites with a higher stand density and very sandy soils. The results have been published in the journal Global Change Biology.

In their study, the researchers specifically selected a wide range of wet to very dry sites, because there are also very dry beech forests here in northern Germany, for example in Saxony-Anhalt. They took numerous wood samples at all sites to measure the annual rings of the trees. -This allows us to look back many decades and reconstruct tree growth in the past,- explains Robert Weigel, a postdoctoral researcher in the Department of Plant Ecology and Ecosystem Research at the University of Göttingen. By intersecting these data with those from climate stations, the so-called -climate-growth relationships- of the trees can be derived.

The investigations revealed that drought and heat in June, the main growth month for beech, are the most important climatic factors influencing thickness growth throughout the study area, with the effects being stronger at drier sites. -But with this look into the past, we are also gaining valuable information about the possible future of beech,- department head Christoph Leuschner is certain.

-The clear message is that dry locations, where water shortages have also increased the most in our region, show the greatest long-term decline in growth," says Weigel. -We see the results as a warning that the red beech will also be increasingly affected by drought here in many regions, and not just in southern Europe. For the future, therefore, it will be necessary to examine more closely where beech forests still have a future in northern Germany and which drought-tolerant tree species will cope better with climate change, taking into account precipitation levels, current climate trends and soil conditions.

Original publication: Robert Weigel et al .Summer drought exposure, stand structure, and soil properties jointly control the growth of European beech along a steep precipitation gradient in northern Germany .Global Change Biology 2022. https://onlinelibrary.wiley.com/doi/10.1111/gcb.16506 .