Pinus uncinata forests occupying hard limestone plateaux of the outer Alps, in the Chablais, the Aravis, the Bauges, the Chartreuse, the Vercors, the Dévoluy in which the almost pure calcareous bedrock is covered by a thick layer of raw humus supporting an acidophilous undergrowth dominated by Rhododendron ferrugineum, Vaccinium myrtillus, Vaccinium vitis-idaea, Vaccinium uliginosum accompanied by Empetrum hermaphroditum, Lycopodium selago, Selaginella spinosa, Cladonia rangiferina, Homogyne alpina, Bartsia alpina, Astrantia minor.