Pinus uncinata forests of siliceous Pyrenean adrets, on schists, granites or gneises, with Arctostaphylos uva-ursi, Juniperus nana, J. hemisphaerica, Calluna vulgaris, Genista pilosa, Cytisus purgans, Cotoneaster integerrimus and a predominantly acidophilous herb layer comprising Deschampsia flexuosa, Cruciata glabra, Festuca eskia, Veronica officinalis, Silene rupestris, Potentilla erecta, Antennaria dioica.