These forests dominated by Pinus sylvestris contain a species-poor herb layer consisting of acidophilous dwarf shrubs and herbs. A moss layer is well developed with the predominance of acidophilous mosses and admixture of terricolous lichens. They occur on rock outcrops in river valleys and sandstone areas, on stabilized sand dunes, sandy products of rock weathering, talus slopes and on serpentine. Pine forests in the most stressed habitats may have remained stable and occurred continuously throughout the Holocene, but others have probably developed as a result of historical forest managament. In the Czech Republic their occurrence is concentrated in the Bohemian Massif. In some sandstone areas they have recently been invaded by the North American eastern white pine, Pinus strobus.