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Vol. 16 (1999) No. 1 p. 25-37




Distribution and developmental patterns of floodplain willow communities were investigated along the Kinu River, which has meandering zone and alluvial fan zone. Community structure, species composition, and alluvial materials of the ground surface were surveyed in 131 stands. 11 Salicaceous species were observed in the study area, and most stands were dominated by 5 major species (Salix chaenomeloides, S. subfragilis, S. gilgiana, S. sachalinensis, S. serissaefolia). Distribution of dominant stands of each species were related with riverbed types ; S. chaenomeloides, S. subfragilis, and S. gilgiana, in meandering zone, S. sachalinensis and S. serissaefolia in alluvial fan zone. Furthermore, some developmental patterns of willow community were clarified in different dominant species. S. subfragilis and 5. gilgiana formed dense juvenile stands on silty or sandy alluvial materials. The stands with these species did not become more than 10m height, even when stem diameter reached to 20cm. On the other hand, S. serissaefolia formed sparse juvenile stands on gravely alluvial materials, and they developed more than 10m height on higher floodplain. These developmental patterns of community were adaptable for river dynamics of their distribution area. S. sachalinensis that had wide distribution area, indicated various patterns of community structure and species composition. The results show that the distribution pattern of willow community is restricted not only by the soil texture suitable for seedling establishment, but also by the relationship between the developmental patterns of community and river dynamics. Especially, development of tree community more than 10m height was dependent on the formation of higher floodplain that is not affectedly flood disturbance.

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