Sub-Atlantic forests of Quercus robur and Quercus petraea, mostly low-canopied, with Carpinus betulus, Sorbus torminalis, Betula pendula, Populus tremula in the subcanopy or the understorey, developed on soils with an alternating hydric regime, mostly clays derived from the alteration of Devonian schists, characterized by the abundance of Carex flacca and the coexistence of acidocline and calcicline species, typical of the sub-Hercynian Fagne-Famenne depression where they constitute a highly distinctive, almost continuous, forest-belt.