Research on an optimal management method of emergent macrophytes by regrowth analysis after cutting aerial shoot

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This research has two main purposes. One is for elucidating the different strategies of two emergent macrophytes, Typha angustifolia and Zizania latifolia, after cutting aerial shoots. Second is to analyze the change of the competitive superiority between Phragmites australis and Miscanthus sacchariflorus.Aerial shoots in T.angustifolia were cut above water in May, July, August in 2003 for investigating their strategy to survive from cutting at different timing. Z.latifolia was also cut in July in 2003. The differences of their strategy for cutting were evaluated quantitatively by re-growth characteristics of aboveground leaves, above-and belowground biomasses, the characteristics of buds and percent allocation of TNC in above-and belowground biomasses just after cutting. The below ground biomass in T.angustifolia decreased about 30% in July cutting, but that in Z.latifolia didn't decrease. Contrary to T.angustifolia that transports below ground material rapidly, Z.latifolia recovered their rhizome not only by re-growth shoots but by many secondary shoots. The secondary shoot formation was assumed also their strategy to protect their habitat.Competition between P.australis, and upland species, M.sacchariflorus, in a river-wetland rehabilitation site was analyzed in relation to flood discharge, flood interval and their stem-breaking moment and by regrowth dynamic model considering their stem-breaking. The decrease in biomass by flood discharge and interval were analyzed for monospecific stands and competitive stand for the two species. If their stem breaking is occurred every year, survival of the two species is difficult. However, if the interval is 2-5 years, they can survive but superiority of M.sacchariflorus is decreased. The analysis indicates that stem-breaking of both two species by flood every 2-5 years can delay the transition from wetland to upland species. Flood disturbance that only breaks stems of P.australis should not be introduced.