Characteristics of floodplain forests and their site conditions in comparison to toeslope forests in the Tokachi river [Hokkaido, Japan]
1996
Aruga, M. (Hokkaido Univ., Sapporo (Japan). Faculty of Agriculture) | Nakamura, F. | Kikuchi, S. | Yajima, T.
Composition and structure of floodplain forests were compared with those of toeslope forests with special reference to site conditions. Site conditions at riparian zone are mainly created by frequent floods, whereas hillslope forests are disturbed rarely by shallow landslides. Floodplain forests indicate a high species richness as they locate away from the active channel, whereas toeslope forests exhibit a relatively uniform, high value of the species richness. Forest stands were classified into three groups by cluster analysis on the basis of the similarity index calculated from basal area of each species. This dendrogram represented tow types of floodplain forests and one type of toeslope forests. Site conditions of both forests were significantly different. Floodplain forests showed a wide range of variance in mean particle size, and low water and organic contents in the soil. We applied the principal components analysis to synthesize a number of site variables. The first principal component (PC-1) was mainly formed by the mean particle diameter, water content and organic content, indicating 40% of contribution. The site conditions expressed by the PC-1 and stability index were clearly different depending on the three forest groups. We concluded that the variety in frequency and intensity of flood disturbances is responsible for creating heterogeneous habitat conditions for forest establishment, which results in a patchy mosaic pattern of floodplain forests in a narrow riparian zone
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