Which provenances of sessile oak are more resistant to climate change: our own native populations or provenances from Belgium or France? And which stands produce the most beautiful and largest trees? To answer these questions, the Centre for Genetic Resources the Netherlands (CGN), in collaboration with Staatsbosbeheer, is conducting trials with as many as 32 different provenances of sessile oak.
What is the sessile oak?
The sessile oak (Quercus petraea) is a native tree species in the Netherlands that is less common than the similar pedunculate oak (Q. robur). The sessile oak is easily recognised by its longer petiole and regularly lobed leaves. Both oak species have an important role in the forest food web. Sessile oak also provides good wood, which is sought after in the furniture industry, for example. The sessile oak can grow on poorer soils and is less drought-prone than the pedunculate oak.
Because of the expected increasing drought stress in the Netherlands, there is growing interest in the sessile oak. The List of Varieties of Trees currently includes autochthonous stands of sessile oak and also recommends several provenances from Belgium. Provenance research is one of the tasks the CGN carries out for the List of Varieties of Trees.
Two trials with sessile oaks from 32 different forests
In the sessile oak trials, trees are grown from acorns harvested from old Dutch oak forests. These are among saplings from Belgium, Germany, France and even a provenance from Austria. Together, these saplings grow up under similar conditions, so that we can ultimately determine which provenances grow well under Dutch conditions.
The trees will be measured regularly for the first 20 years. First, survival and time of leaf sprouting will be assessed. Stem shape, height and diameter growth can only be assessed when the trees are older.
As soil is also important, the trial is being conducted both on a poorer sandy soil in Amerongen and on a richer old arable field in Drenthe. Three similar trials are also being constructed in Belgium by INBO, our Belgian colleagues. To give the trees as much opportunity as possible to mature undisturbed, both trial fields have been fenced. In this way, the tree saplings are protected from chewing and rubbing damage by deer.
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