PRESS RELEASE – Forest planting may contribute to mitigate climate change. The origin of seeds is crucial to optimise the success of tree planting and the adaptation of forests to future climates. INRAE and ONF (French Forest Office) conducted a vast study over 30 years using a collection of around 100 populations* of sessile oak (Quercus petreae Matt. Liebl.) from all over Europe and grown in four experimental sites in France to identify the best seed sources for this species. Their results, published in Annals of Forest Science, show that tree populations from regions with a long tradition of forestry have the best combination of ecological and silvicultural traits (survival, growth, form, adaptation to climate variations). The scientists recommend using about 30 seed sources for planting sessile oaks in France, combining the diversity and adaptation needed to respond to climate change.
The strong drought episode of 1976 that affected France and part of Europe between autumn 1975 and summer 1976, resulted in an increased mortality of forest trees, particularly pedunculate oaks (Q. robur L.). These die-offs prompted research into the adaptation of oaks in general and sessile oak in particular, which remains the most widely planted deciduous tree species in France. ONF and INRAE joined forces and assembled a collection of 110 sessile oak populations from France (70 populations) and Europe (40 populations) on four experimental sites located in the French departments of Sarthe, Cher, Nièvre and Moselle. For thirty years, the scientists followed the characteristics of interest of these oaks (survival, growth, shape, adaptation to climate fluctuations) and their genetic variability. The aim was to identify the best seed sources for planting sessile oaks capable of adapting to future climates.
Surprisingly, the research team found that oak populations with similar traits and genetic variation did not cluster according to the 19 geographical areas of origin of sessile oaks, areas defined by their climatic homogeneity (so-called ‘regions of provenance’). Instead, the study showed the effects of silviculture on the organisation and variation of oak traits. Thus, oaks with the best compromise between survival, growth, adaptation to climatic variations and tree form came from regions with a long tradition of forestry and silviculture, sometimes going back to the Middle Ages, such as Bourbonnais, Berry and the Loire Basin. In these regions, the trees have been selected for these characteristics by human intervention over several generations.
The scientists make several recommendations for successful plantations of sessile oaks that contribute to the adaptation of forests to future climate conditions. They identified 34 oak populations with optimal combinations of traits as seed sources for future plantations. They also highlight the importance of mixing seed sources to maintain genetic diversity in plantations, which is essential for adaptation to the ongoing climate change.
These results were published in the international research journal “Annals of Forest Science” under the form of a research paper accompanied by a data paper presenting the huge data set produced by this long-term experiment. The data have been deposited into the repository Data-INRAE and have been processed to comply with the “FAIR” requirements. This combination makes sure that the research results analysed in the first paper are reinforced by the presentation of the data and by the fact that the data are reusable and accessible.
* A population of a tree species refers to a group of trees coming from the same region and having grown in the same environment (soil, climate, forest management…).
 Girard, Q., Ducousso, A., de Gramont, C.B. et al. Provenance variation and seed sourcing for sessile oak (Quercus petraea (Matt.) Liebl.) in France. Annals of Forest Science 79, 27 (2022). https://annforsci.biomedcentral.com/articles/10.1186/s13595-022-01140-0
 Ducousso, A., Ehrenmann, F., Girard, Q. et al. Long-term and large-scale Quercus petraea population survey conducted in provenance tests installed in France. [Data paper]. Data INRAE repository. Annals of Forest Science 79, 26 (2022). https://annforsci.biomedcentral.com/articles/10.1186/s13595-022-01141-z
Antoine KREMER UMR BIOGECO – INRAE
Alexis DUCOUSSO UMR BIOGECO – INRAE
Quentin GIRARD UMR BIOFORA – ONF ORLÉANS
Brigitte MUSCH UMR BIOFORA – ONF ORLÉANS