Rolling down that mountain: Mont Ventoux's beech comeback

The beech stands of Mount Ventoux (France), at the southern margins of the species’ distribution, have been continuously shrinking until the middle of the nineteenth century. By then, only a small forest patch was left, likely covering less than 100 hectares, close to the mountain top.

Then, a combination of rural abandonment and reforestation programmes favoured the expansion of beech down the slopes of the mountain, and in less than a century—that is, between two and four tree generations—beech stands established at all altitudes between 1500 and 800 metres a.s.l., expanding at least 10- to 20-fold.

In the process, the new beech stands occupied increasingly warm habitats and became adapted to their new environment. This is visible in adaptive characters, such as the dates of budbreak (Gaüzère et al. 2020); in this study, the research scanned the genome of the Mount Ventoux beech populations in search for evidence of molecular adaptation. They found that about twenty regions of the genome are more different between high- and low-elevation stands than they may be solely due to random fluctuations of gene frequencies. This differentiation between forests living at different altitudes unfolded from genetic diversity that was already present in the relict forest patches. This suggests that genetic adaptation can happen over few decades, and that tree stands adapted to colder conditions can quickly adapt to warmer temperatures: a demonstration of the vast adaptive potential of trees, that management can contribute to enhance, and a beacon of hope for adaption to climate change.