抄録
The purpose of this paper is to clarify the influence of physical conditions on the distribution of riverine plant communities. Full vegetation survey was performed in 1994 and 1997, on an alternating bar formed in a downstream reach of the Yoshino River, Shikoku, Japan. Comparison of two vegetation maps for the two years, including two woody and fifteen herbaceous communities, reveals characteristic changes of plant communities. Five factors, namely bed-level variation, absolute bed-level fluctuation, relative bed-level from the surface of low-water stream, duration of inundation and shear velocity of flooding flow, were defined and evaluated to describe the physical conditions at many reference points distributed on the bar. Community-specific spatial averages of the five factors are not uniquely related with individual plant communities, however their combinations appear to be characteristic of some ecological groups of plant communities. It is suggested that the five factors will be effective for distinguishing the physical conditions to sustain the ecological groups.
