Abstract
In order to quantify the water quality improvement method by direct removal of the biomass of Phragmites australis which accumulates nutrient salts, the biomass of Phragmites australis under various temperature curve and daily global radiant flux were analyzed and the nutrient content were calculated. The variation of the biomass was related to the total accumulated temperature of early growing season by stored material of rhizomes and of photosynthetically growing season, and the ratio of the respective accumulated temperature. Analysis of annual flux showed that the respiration of aboveground and belowground plant organs was an unavoidable component and changed the energy budget of utilizing photosysthesized materials, caused the variaiton of the biomass. The removable quantity of nutrients of aboveground biomass was changed drastically with respect to the harvest day
