Siliceous rock walls and cliffs in the nemoral region except those in the high mountains and coastal cliffs subject to sea spray. They comprise diverse metamorphic, sedimentary and igneous rocks but also some non-calcareous but more or less base-rich igneous volcanics. The vegetation in the rock fissures and crevices consists of vascular plants such as small ferns, succulents and rosulate herbs, on the rock surface also mosses and hepatics, crustose and foliose lichens, micro-algae and other micro-organisms. Natural succession can lead to scrub and woodland development.