A research team is analyzing the genes of those trees that can cope well with drought / whose offshoots are supposed to save the forest
The spruce barely stands a chance in many locations. Heat, drought and bark beetles kill it. For a long time, hopes for a climate-stable forest conversion rested on the beech, which seemed to be able to cope better with the changes. But the dry years from 2018 to 2020 showed that this tree species also suffers severely. Anyone walking through the woods cannot overlook it: Many beeches have died, others have dry branches or they have only sparsely sprouted. A research team has now developed a method to perhaps save the beech tree after all.
The starting point for the team around Frankfurt professor Markus Pfenninger was an observation in Hessian forests: “In beech forests, not all trees are damaged in the same way. Completely healthy trees stand right next to severely damaged trees, ”reports the biologist. Such unequal couples can be found everywhere. Why this is so lies in the genome of the trees, as Pfenninger and colleagues found out with DNA tests on around 200 pairs of trees. Thanks to such tests, resilient specimens could be selected for forestry and used in reforestation in the future.
According to the experts, the complete genetic information of the beech in the form of DNA comprises around 542 million building blocks. Some of them are identical in all specimens of the tree species, but others differ from tree to tree. “This is exactly the case with healthy and severely damaged beech trees, as the genome analysis shows,” the team said. According to this, around 100 DNA segments are crucial for drought resistance in healthy trees; they enable a reaction to drought stress. “The individual genetic makeup determines whether a beech can survive longer dry periods”, explains Pfenninger, who conducts research at the “Senckenberg Biodiversity and Climate Research Center” in Frankfurt and teaches at the University of Mainz. Researchers from the universities of Frankfurt and Gießen, the TU Darmstadt and the Hochschule Geisenheim University were also involved in the study. The study has been published in the specialist magazine “eLife”.
Based on the DNA results, the team has developed a test that can be used to detect drought resistance in the seeds’ genetic makeup. Senckenberg researcher Barbara Feldmeyer explains: “If we classify individual trees, foresters can specifically rely on particularly resistant trees, for example for reforestation.” This means that beech forests are “sustainably prepared for climate change”.
against “wood factories”
Nature conservation initiatives complain on the “Beech Forests Day” on June 25th that the beech forests in Germany are in a “precarious situation”. The pressure to use has increased significantly, although five German beech forest areas were included in the Unesco World Heritage list ten years ago, including the Hessian Kellerwald-Edersee National Park.
In an open letter, they demand that politicians end the “still prevailing timber factory economy”. In the current situation, the protection of forest ecosystems must have priority over all economic considerations. The signatories are 60 nature conservation associations and forest experts, including the Deutsche Naturschutzring, BUND and Robin Wood. jw
The common beech (Fagus sylvatica) is widespread in Europe and with a good 15 percent share it is the most common deciduous tree in German forests. If humans did not intervene, forests in this country would largely consist of beeches. The tree species with its initially light green, later leathery leaves can cope with different site conditions and plays an important role in near-natural forest management. It provides a habitat for several thousand species, including beetles and larvae or woodpeckers.
Success rate: 99 percent
In the dry years, the deep-rooted trees were often no longer able to reproduce enough fine roots that are necessary for their water supply. Other problems are infestation with wood-decomposing fungi and pests. The bark of many beech trees has also been torn open by sunburn, a gateway for fungi and insects.
For their work, the Pfenninger team examined beeches throughout Hesse in 2019 and 2020, from the Odenwald in the south to the Westerwald and northern Hesse, also in the Rhine-Main area. At each of the approximately 200 locations, they selected a healthy-looking tree and a tree five meters away on average with missing or severely dried leaves. The DNA was then obtained in the laboratory from the leaves, which were still green. The team then checked the test that was then developed, which works with molecular markers for the drought-resistance genes, on around 90 beech trees. Result: “The success rate was 99 percent.”
Pfenninger explains: “With our study we have laid the scientific basis for a sustainable management of beech forests that supports the natural selection of resilient trees.” Now it is a matter of putting the findings into practice. Examples are the monitoring of natural forests or selective deforestation and reforestation. “In this way we can help to maintain a unique ecosystem that is already feeling the effects of climate change,” says the biologist, “because the next hot summer will come – sooner or later.”
