Pioneer formations of humid calcareous sands of Atlantic and sub-Atlantic Europe, recorded from the North Sea coasts of northern France, Belgium, the Netherlands, England, Germany and Denmark, and from the Baltic coast of Germany, with Samolus valerandi, Centaurium littorale, Centaurium erythraea, Centaurium pulchellum, Gentianella amarella, Blackstonia perfoliata, Juncus bufonius, characteristic of humid dune slacks and dune pool fringes, on soils with low salinity.