Press release: Trees in extreme drought in Germany
No. 104 - 11.08.2026
Researchers at Göttingen University study influence of soil and landscape on health of beech trees
Forests in many regions of the world are increasingly under stress caused by drought as a result of climate change. Even forest ecosystems traditionally considered to be water-rich are being affected by prolonged periods of drought with increasing frequency. Since 2021, researchers from the University of Göttingen, in collaboration with the nearby Lauterberg Forestry Office, have been investigating how soil moisture affects the vitality of beech trees in the Harz Mountains in Germany. The results were published in the journal Trees.
The key factor in the survival of trees during periods of drought is how long the soil can retain water. Using sensors, the team continuously monitored the water content at various soil depths. The area studied is in the Harz Mountains. This is one of Germany’s forested regions with the highest rainfall, yet it too is increasingly suffering from dry spells. Spruce trees in this area are dying rapidly due to bark beetles, while beech trees are slowly losing their vitality. The researchers compared two groups of beech trees on a slope with similar soils: a healthy group in the lower part of the slope, where water collects as it flows downhill, and a group which is already damaged on the upper part of the slope, which dries out more quickly. During the extreme drought of the summer of 2022, the soil on the upper slope remained dry – even when measured to considerable depths for several weeks, despite short periods of rain. In the lower part of the slope, however, even light rainfall was enough to replenish the soil with water, resulting in significantly shorter dry spells for these trees.
The team of researchers analysed the soil to find out why these groups of trees reacted so differently to drought despite similar levels of rainfall. The forest floor consists of two layers: the upper layer, about 50 centimetres thick and composed of soil which is a mixture of sand and clay – it stores most of the water and is well-penetrated by roots; then there is a layer underneath made up of coarse stones that can hardly store any water. It is the second lower layer which drains water downhill and this takes water from the upper levels. As long as there is sufficient rainfall, this soil structure is not a problem. However, during prolonged dry spells, the structure is a clear disadvantage: the soil dries out more quickly, and less and less water is available for the trees.
“The damage caused by the soil structure results in damaged beech trees which have a sparser canopy. As a result, more sunlight reaches the ground, which exacerbates the problem by warming up the ground so that it dries out faster,” explains lead author Dr Michael Klinge at Göttingen University’s Department of Physical Geography. “To reliably detect drought stress in beech forests, hydrological processes in the soil must be taken into account, in addition to measurements about the climate. In the future, forest management policy should pay more attention to soil structure and the shape of the landscape. Our research showed that on the upper slopes, it is better to plant drought-tolerant trees as the trees there are increasingly under water stress due to ongoing climate change,” says Klinge.
Original publication: Klinge, M. et al. Soil-moisture dynamics across contrasting levels of beech forest vitality under extreme drought in the Harz Mountains, central Germany. Trees (2026). DOI: 10.1007/s00468-026-02788-1
Contact:
Dr Michael Klinge
University of Göttingen
Institute of Geography – Department of Physical Geography
37077 Göttingen, Germany
Tel: +49 (0)551 3928058