Salix spp. scrub or arborescent formations, lining flowing water and submitted to periodic flooding, developed on recently deposited alluvion. Willow brushes are particularly characteristic of rivers originating in major mountain ranges. Shrubby willow formations also constitute an element of lowland and hill riverine successions in all major biomes, often making the belt closest to the water course. Taller arborescent willow formations often constitute the next belt landwards in riverine successions of lowland western nemoral, eastern nemoral and warm-temperate humid forest regions, and a large part of the less diverse riverine systems of the steppic, mediterranean and cold desert zones. Vegetation of alliance Salicion albae, species Salix alba, Salix fragilis, Populus alba, Populus nigra, Populus canescens, Lycopus europaeus, Lysimachia vulgaris, Phalaroides arundinacea and Urtica dioica. May be affected by the invasive alien species Solidago canadensis, Aster novi-belgii, Aster novi-anglii, Impatiens glandulifera.