Pinus uncinata forests of the western outer Alps, the Jura and Pyrenean ubacs, developed on siliceous or decalcified soils of the sub-alpine level with a predominately ericaceous undergrowh comprising Rhododendron ferrugineum (dominant), Vaccinium myrtillus, V. uliginosum, Calluna vulgaris, Homogyna alpina, Deschampsia flexuosa, Lycopodium annotinum.