Pinus uncinata forests of ubacs of the Pyrenees developed on siliceous soils, or on decalcified soils in the calcareous ranges, in the more humid and snowy parts of the sub-alpine level, with a ground layer dominated by Rhododendron ferrugineum accompanied by Vaccinium myrtillus, Homogyne alpina, Rosa alpina, Deschampsia flexuosa, Oxalis acetosella, Juniperus nana, Calluna vulgaris, Dryopteris linnaena, Polystichum spinulosum, Solidago virgaurea.