Acidophile or acidocline snow-patch and snowbed communities of the boreal and arcto-alpine mountains, dominated by dwarf willows. Creeping species dominate, adapted to the short growth season in areas covered by snow for up to eight to ten months. Typical species: Salix herbacea, Carex firma, Dryas octopetala, Salix retusa, Aster alpinus and Carex sempervirens. Endemic species are also often found.