EVALUATION OF RUNNER EXPANSION LENGTH AND PRODUCTIVITY BY Phragmites japonica ON THE RIVER BAR

Abstract

For elucidating the fundamental characteristics of Phragmites japonica that grow on a gravel-bed river bar in middle stream of Ara river, artificial sedimentation experiment on the plants' colony was conducted and the strength of runner was measured by push-pull gauge. Quadrates were set and runner expansion was measured seasonally. Sedimentation experiment with 0.1m thickness on May had no effect on the growth of P. japonica. The length of runner is closely related to the cumulative shoot height of parent colony of the runner. Even the newly formed colony has enough strength to stand against the high velocity. The velocity is higher than that for the initiation of the gravel movement. Then the lateral distribution and their seasonal development of the colony is very important to evaluate their effect on the flow resistance. Dynamic growth model of P. japonica formulated by using the lateral enlargement characteristics of the runner has a potential to express the seasonal variation of shoot biomass and lateral biomass distribution.