Abstract
The movement of a threatened plant Ludwigia peploidea ssp. stipulacea in Kashio river eastern part / Kanagawa, was investigated from 1998 to 2001 over four years. The abundance of this threatened plant became 6 or more times in four years. Formation of the new sandbank accompanying precipitation with few first summers was participating in increase of its abundance. The stage was accepted in succession process an initial stage and the second half. The initial stage showed the appearance of community in which most sandbanks were covered with L. peploidea ssp. stipulacea. The stage of the second half showed the appearance of one, which served as order of Ambrosia trifida L., Persicaria lapathifolia S.F.Gray, and L. peploidea ssp. stipulacea from the center of a sandbank in concentric circle toward a border. It was suggested that the abundance of L. peploidea ssp. stipulacea in each sandbank became the maximum immediately after shifting to a stage of the second half from an initial stage.
