The Nature Restoration Law approved by the EU Commission in 2024 commits Member States to restore 30% of degraded habitats by 2030. The achievement of this ambitious goal poses several challenges, including the ability to predict the outcome of artificial interventions and to what extent they can restore or initiate dynamics leading to ecosystems that become stable over time and are similar to those resulting from natural evolutionary processes. The lack, or fragmentation, of historical data concerning past land use and human interventions greatly reduces our understanding of the legacy of such activities.

A plantation of Quercus robur L. (English oak) mixed with Fraxinus angustifolia Vahl (narrow-leaved ash) set up in 1985 in an area used for centuries as pasture and then for farmland and bordering on an old-growth forest classified as Fraxino-Quercetum roboris, Gellini et al. 1986, gave us the opportunity to compare understorey vegetation originating from long-term natural forest dynamics with that derived from secondary colonization after treefall. The understorey vegetation was analysed for composition and abundance in plots arranged in mature forest stands (MF), in natural forest gaps (FG), and within the artificial plantation (AF). Species richness and cover/abundance following Braun-Blanquet were determined on five 400-square-metre plots for each vegetation type. The occurrence of species in 16 quadrats (50x50 cm) set along the plot diagonals was used to estimate vegetation diversity.

After forty years, AF shared 60% of species with MF and was populated by typical nemoral species. Species richness was almost double in FG than in forests, but the proportion of alien species was 7% compared to 2.5% in MF and 0% in AF.

These results provide valuable insights into the ability of artificial forest plantations to restore natural habitats, provided that connectivity with natural systems is maintained to ensure the supply of forest species propagules.