Abstract
Distribution and species composition of Alnus firma communities on floodplains were studied in mountainous zones of central Honshu, Japan. In this study, all stands were identified to Calamagrostio-Alnetum firmae Miyawaki Okuda & K. Fujiwara 1971. These stands were divided phytosociologically into two subassociations, subassociation of Salix sachalinensis, and typical subassociation, respectively. The subassociation of Salix sachalinensis was divided further into three variants, and the typical subassociation divided into two variants. The result of DCA analysis suggested that snowfall conditions and altitude were the main factors affecting differentiation of these vegetation units. The relationship between vegetation units and environment may be explained by differences of site stability, water-holding capacity of deposits and seasonal patterns of water discharge.
