Mediterranean multi-layered riverine forests of base-rich soils submitted to seasonal prolonged inundation with slow drainage, with Populus alba, Populus nigra, Fraxinus angustifolia, Ulmus minor, Salix alba, Salix spp., Alnus spp., lianas and often species of the Quercetalia ilicis, distributed in the mediterranean regions of the Iberian peninsula, southern France, the Italic peninsula, the large Tyrrhenian islands, the Hellenic peninsula, the southern Balkan peninsula, North Africa, and their zones of transition to adjacent climatic zones. Formations physiognomically dominated by tall Populus alba and/or Populus nigra are listed here. The poplars may, however, be absent or sparse in some associations which are then dominated by Fraxinus angustifolia, Ulmus minor and/or Salix spp. Such ensembles are listed under units G1.1121 or G1.33. The poplar forests are usually the tall ligneous vegetation belt closest to the water in riverside catenas.