Open lowland and hill rock debris swards of suboceanic, temperate, boreal or sub-Mediterranean, climates of Western Europe and of Central Europe, east, sporadically, to the Baltic countries and the Black Sea, formed mostly by annuals and succulents or semisucculents on decomposed rock surfaces of edges, ledges or knolls, with calcareous or siliceous soils frequently disturbed by erosion or rabbits. Vegetation communities are of Alysso-Sedion albi and Seslerio-Festucion pallentis. These swards comprise a great variety of distinct and often very local, isolated communities harbouring many characteristic species like [Erophila verna], [Poa bulbosa], [Sedum acre], [Sedum album], [Sedum sexangulare], among which are numerous rare forms including both relict and evolutionarily recent taxa. Together with more evolved grassland communities of unit E1.29, sometimes E1.21-E1.25, E1.27, or E1.281, very paucispecific communities of units H3.19 or H3.2B, and lacunar shrub formations of unit F3.1, they constitute the vascular vegetation of middle European inland cliffs and rock outcroppings of unit H3 (namely H3.1B, H3.1C and H3.2E).
