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What is the new drought stress experiment about?
The experiment that has just started is investigating how different provenances of sessile oak react to drought. The trial on our Drylab (outdoor dry laboratory) is part of the Dutch research project BEHOUD (Dutch for "preservation" or "conservation"). The seeds of the young seedlings come from various regions of Europe (two regions in the Netherlands, two in Germany) where the sessile oak is native. The researchers suspect that the seeds (and the trees growing from them) from the drier regions are already better adapted to drought than the seeds from the wetter provenances. The sessile oak was chosen for this experiment because it is already well adapted to drought. Therefore, the demand for sessile oak seeds and seedlings is high for the conversion of coniferous forests to climate-adapted mixed forests.
How does the experiment work?
The acorns were collected last winter and sown at the Thünen Institute of Forest Genetics in Großhansdorf, where they were nurtured and cared for for a growing season. In November 2025, the plants were moved to the Thünen Institute of Forest Ecosystems in Eberswalde. They were planted this autumn to minimize transplant stress. They will be kept under optimal conditions until spring 2026. Then, the drying process will begin. The roof of the dry lab can be automatically closed in case of rain. This allows the plants in the lysimeters to be protected from the rain and subjected to drought stress. The control trees, on the other hand, will continue to be irrigated. Numerous parameters will then be measured on the trees. Based on characteristics such as the number of leaves or the size of the shoots, we can already draw initial conclusions about how the origin of the seeds influences the trees' resilience to drought. The researchers will continue to monitor which trees are the first to suffer from the drought, and which may even die. Since it is quite possible that the young plants will recover in the next growing season in spring despite the drought stress, the experiment will continue until 2027.
