Typical beech forest in northern Germany: the scientists took samples of wood from dominant trees at 30 locations.
Photo: Banzragch Bat-Enerel
The scientists took samples of wood from major trees in 30 different locations so that comparisons could be made between areas with different average rainfall levels. They then analysed the tree rings to obtain a retrospective measure of tree growth.
The news release from Georg-August-Universität, Göttingen, describes the study and its significant findings:
Research team at the University of Göttingen finds widespread drought stress in European beech.
More and more trees are suffering the consequences of decades of man-made climate change. The growth of the European beech has so far suffered decline mainly in southern Europe. European beech is Germany's most important native forest tree species and it is most commonly found in Central Europe. A research team from the University of Göttingen has now been able to show that the European beech is suffering from increasing drought stress in summer in northern Germany as well. This climate stress is particularly pronounced at warmer sites, when there is a higher density of these trees together, and on very sandy soils. The results have been published in the journal Global Change Biology.Samples of wood are taken from European beech. They are glued to wooden strips and prepared with razor blade or sandpaper so that the annual rings are clearly visible on the smooth surfaces and can be measured and dated using a microscope.Photo: Stella Gribbe
This allows us to look back over many decades and reconstruct tree growth in the past.
The clear message is: dry locations show the strongest long-term decline in growth, because a lack of water is becoming much more common there. These results are a warning that the European beech will also be increasingly affected by drought, not just in southern Europe, but also in many regions here in Germany.
Dr Robert Weigel, senior author
Plant Ecology and Ecosystem Research
University of Göttingen, Göttingen, Germany.In their study, the researchers specifically selected a wide range of sites ranging from wet to very dry, because even in northern Germany there are very dry beech forests. The scientists took numerous wood samples at all these sites to measure the tree rings in the tree trunks. These data were combined with those from climate stations, to derive the relationship between climate and growth of the trees.Looking back into the past in this way enables us to gain valuable information about the potential future of beech.
Professor Christoph Leuschner, co-author
Head of Plant Ecology and Ecosystems Research
Göttingen University, Göttingen, Germany.
The investigations revealed that drought and heat in June, the main month of growth for beech trees, are the most important climate factors influencing how much the trunk will grow across all the locations studied, with the negative effects being stronger in drier locations.
For the future, therefore, it will be necessary to examine more closely where beech forests will be able to grow in northern Germany and which drought-tolerant tree species will be better able to cope with climate change, taking into account the amount of rainfall, current climate trends and soil conditions.
More details are given in the abstract to the team's paper published open access in the journal, Global Change Biology:
AbstractAs global temperatures continue to rise, we can expect the effects of drought and higher mean temperatures in sme areas and of increased rainfall and flooding in others to continue to increase and become ever more extreme, losing valuable biodiversity and increasing species extinctions, at least locally.
Increasing exposure to climate warming-related drought and heat threatens forest vitality in many regions on earth, with the trees' vulnerability likely depending on local climatic aridity, recent climate trends, edaphic conditions, and the drought acclimatization and adaptation of populations. Studies exploring tree species' vulnerability to climate change often have a local focus or model the species' entire distribution range, which hampers the separation of climatic and edaphic drivers of drought and heat vulnerability. We compared recent radial growth trends and the sensitivity of growth to drought and heat in central populations of a widespread and naturally dominant tree species in Europe, European beech (Fagus sylvatica), at 30 forest sites across a steep precipitation gradient (500–850 mm year−1) of short length to assess the species' adaptive potential. Size-standardized basal area increment remained more constant during the period of accelerated warming since the early 1980s in populations with >360 mm growing season precipitation (April–September), while growth trends were negative at sites with <360 mm. Climatic drought in June appeared as the most influential climatic factor affecting radial growth, with a stronger effect at drier sites. A decadal decrease in the climatic water balance of the summer was identified as the most important factor leading to growth decline, which is amplified by higher stem densities. Inter-annual growth variability has increased since the early 1980s, and variability is generally higher at drier and sandier sites. Similarly, within-population growth synchrony is higher at sandier sites and has increased with a decrease in the June climatic water balance. Our results caution against predicting the drought vulnerability of trees solely from climate projections, as soil properties emerged as an important modulating factor. We conclude that beech is facing recent growth decline at drier sites in the centre of its distribution range, driven by climate change-related climate aridification.
Weigel, R., Bat-Enerel, B., Dulamsuren, C., Muffler, L., Weithmann, G., & Leuschner, C. (2022).
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, 00, 1– 17. https://doi.org/10.1111/gcb.16506
Copyright: © 2022 The authors.
Published by John Wiley & Sons, Inc. Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
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