Abstract
Distribution of four woody plant communities, Salix chaenomeloides community, S. gracilistyla community, Alnus serrulatoides community and Elaegnus umbellata community, is described in relation to their habitat characteristics in middle and lower reaches of the Naka River, Shikoku, Japan. Two Salix communities are distributed at the most unstable sites, close to low water channel where flood disturbance frequently occurs. This is due to on the necessity of water for their germination from their seeds. S. chaenomeloides prefers gravel bar composed of rather finer sediments in lower reach, while S. gracilistyla prefers rocky beds in upper reaches. A. serrulatoides occurs on middle part of rocky beds or some of alternative bars in upper reach. E. umbellate occurs on the highest part of huge rocks or gravel bars in upper and lower reaches. A. serrulatoides and E. umbellata can colonize at nutrient-poor sites due to their nitrogen fixation ability. E. umbellata communities in lower reach have been established from the 1980s. This might relate to their seed -dispersal trait that seeds are carried by birds. These ecological traits have to be considered to develop techniques for managing riparian plant communities
