On a rainy fall morning, half a dozen forestry technicians of Andaine forest, in the south of l’Orne, are preparing to carry out an unprecedented operation of beech hammering.
Equipped with a hammer and a spray of paint, they will walk through plot 233 to mark the beeches that they deem already dead, victims of three consecutive years of extreme heat and droughts. So hammered, these hardwoods can be felled by the summer, and sold before losing their market value.
A rating of dieback
A few minutes from the start, Guylène Mathieu, from the ONF (National Forestry Office) forest health department, presented them with the new Deperis scoring system, to assess the health of beech trees. The rating goes from “Very healthy” (A) to “Very wasting away” (F). “We note from two criteria: the lack of ramifications and branch mortality, she explains. Trees marked E and F are dying. You have to hammer them, because they will not recover in the spring. “
Technicians have observed since this summer that the beeches of the Andaine forest are less abundant, and that their branches sometimes dry out in spring. However, beech represents a quarter of the trees in this forest. “It is not a massive dieback, but there are starting to be signs”, details Guylène Mathieu.
A tree that gets damaged very quickly
“Beech is an extremely sensitive tree, Judge Samuel Autissier, director of the ONF territorial agency of the former Basse-Normandie. As soon as there is a beginning of withering, there is rarely a turning back. It is a tree which deteriorates very quickly and can die in two or three years. “
Determining wasting is more difficult than it seems and technicians are invited to discuss with each other if they have any doubts. “Perhaps a beech tree that is losing its leaves is not dying, but has adopted a strategy to respond immediately to the drought. It is even these trees that are perhaps more adapted that will re-leaf in the spring. “
Romuald Heslot, forestry technician, has observed this decline of beech trees for several years. While making a cut about twenty centimeters long in a tree, he explains that “If we look up, we see that this tree has no more leaves and many dead branches. As it is along a very busy path, to avoid any risk of falling wood, I prefer that it be removed. “
A water-hungry essence
The ornate technician makes a second notch on the other side of the tree, and takes out his spray of lacquer a resolutely pink flashy. He marks the tree so that the loggers can see it from a distance.
“Beech, which is a water-hungry species, begins to suffer, he continues. We have a lot of water in winter and relatively little in summer. For two years, I have noticed that a little east wind dries up the vegetation and the soil part of the year. It’s worrying. What is happening now, we were told for 80 years! “
The speed of climate change has taken a sector that works in the very long term by surprise. “We are cultivating for in 100, 120 years, says Christian Clément, head of the Bocage territorial unit at the NFB. Decline is not something that we fully control, between the progress of research, management and our budgetary constraints, there are more questions than answers. “
A range of answers
Several solutions are being tested: the “loosening” of the forest, to prevent beeches from competing for water resources, the diversification of tree species, to have a mosaic forest, work on genetics, to introduce trees. more resistant in the middle of a stand which would regenerate naturally … Experiments are numerous.
Review of the day: twenty-seven hammered beeches. Good news ? “We have seen dozens, if not a hundred heavily leafless trees that will require passage in the spring, explains Romuald Heslot. I am still worried. I am sure that the little heat we had in September has given another layer. “
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