Development of aquatic plant model and analyses of carbon & nutrition dynamics in lake/river environment

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Aquatic plants have an important role in water quality in lakes and rivers. Difficulties to evaluate efficiency, however, have made it hard to introduce the plants system into practical managements. Under such circumstances, necessary datasets were obtained from the field observation and then sub-modules were made, aiming to finally develop the mathematical tool available in management. In the field observation, material translocation system was measured for some of important emergent species such as Phragmites australis, Typha augustifolia and Zizania latifolia, by sampling shoots and rhizomes monthly. It was also obtained for the population cut in summer time, often conducted to harvest nutrient from water. Based on these results, the growth model was developed for these species. Then the model was applied to obtain important characteristics regarding the growth characteristics under various conditions, efficiency in nutrient harvesting, nutrient cycle through the plant body, etc. The following results were obtained : 1)Carbon, nitrogen and phosphorus cycles was obtained in the Phragmites australis stand in Nieseidlarsee in Austria. 2)Latitudinal effects were obtained for above and belowground biomass of Typha spp. in the equilibrium, stage under a fixed seasonal meteorological patterns with respect to latitude. The function of secondary shoot formation was elucidated as latitude specifically. 3)The competition of two emergent species was evaluated by the model. 4)The amount of harvested nutrients by cutting was evaluated by the model and the best cutting time to remove nutrients was obtained. Other than these results regarding emergent species, the competition between the submerges species, Potamogeton perfoliatus and epiphyton, and the accumulation rate of organic materials in the flowing water by Potamogeton spp. were obtained.