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Has files: YesSubject: search.filters.subject.Phragmites australis

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    PublicationOpen Access
    Evaluation of the recovering process of Phragmites australis after cutting by the dynamic regrowth model and the validation by the observation
    (Ecology and Civil Engineering Society, 2004-03-30) YUTANI, K; ASAEDA, T; TANAKA, N; KARUNARATNE, S
    Mowing is a general reed bed management method for the restoration of devastated wetlands and the maintenance of plant diversity in wetlands. Based on the reed growth model that has been developed in recent years, the reed reed length model as a wetland management method Was developed based on the observation results. In the wetlands of Akigase Park in Saitama City, Saitama Prefecture, three years of observations were carried out to investigate the recovery process of reed beds from cutting. Although it had the most adverse effect on the growth of Phragmites auspicus, the proportion of leaves of regenerated shoots after cutting was increased from 0.28 to 0.56 for June and July cutting. June cutting reduced shoot height and dry weight and rhizome dry weight. On the other hand, Yoshi recovered from summer cutting in about 2 years, and reed bed management was performed every 1 or 2 years. The improved reed-cutting regeneration length model, which was shown to be necessary, well reproduced the observation results and the data from the previous literature regarding cutting and field burning. As a result of model calculation, the reeds that grow in a well-nourished environment It was shown that it recovers from cutting in about 3 to 4 years, but it may take 10 years or more for reeds that grow in poorly nourished environments.
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    PublicationEmbargo
    Seasonal fluctuations in live and dead biomass of Phragmites australis as described by a growth and decomposition model: implications of duration of aerobic conditions for …
    (Elsevier, 2002-07-01) Asaeda, T; Hietz, P; Tanaka, N; Karunaratne, S
    We developed a model of Phragmites australis growth and decomposition to evaluate the material budget and nutrient cycles of a reed stand in Neusiedlersee, Austria. The model describes the growth of each organ of P. australis, the collapse of standing dead shoots, the decomposition of leaves and stalks, and nutrient uptake and release during these processes. The model was calibrated using growth and decomposition data from the literature, and subsequently applied to predict the effects of P. australis stands on a marsh ecosystem. From the start of its decomposition in water, the litter was assumed to stay in the aerobic water layer for 6, 12 or 24 months before entering the anaerobic sediment layer. Because decomposition increases with increasing oxygen and temperature, the aerobic decomposition rate (before the litter was transferred to the anaerobic substrate) increased markedly, especially from spring to autumn. The model predicted that between 33 (6 months aerated) and 48% (24 months aerated) of the annual aboveground production would decompose within 1 year, while the rest would remain in the anaerobic substrate. Rates of nitrogen and phosphorus release were 1.4 times higher between late spring and the end of summer than during autumn and winter. A higher proportion of phosphorus than nitrogen was expected to remain trapped in the anaerobic layer. The uptake of nitrogen and phosphorus during the growing season exceeded release during decomposition 4–6 and 5–7-fold, respectively. The model is useful for quantifying the nutrient cycles of reed-dominant marshes.
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    PublicationEmbargo
    Dynamic modeling of the growth of Phragmites australis: model description
    (Elsevier, 2000-08-01) Asaeda, T; Karunaratne, S
    A dynamic model was developed to simulate the growth dynamics of a monospecific stand of Phragmites australis in freshwater ecosystems. Five state variables (biomass of shoots, inflorescence, roots, old rhizomes and new rhizomes) were selected to illustrate the growth of P. australis. Growth was described using mathematical relationships. The net growth of the plant stand was the integral effect of photosynthesis, respiration, mortality and assimilate translocation between shoots and below-ground plant organs. Below-ground biomass (i.e. rhizome and root biomass) before the growth commencement, daily total global radiation and daily mean air temperature were input data. The model is capable of simulating the seasonal variation of above-ground biomass (shoots, stems, leaves and panicles), leaf area index, rhizome, new rhizome, root biomass and shoot height with correlation coefficients close to 1.0 for most of the parameters. The model estimated the conversion efficiency of photosynthetically active radiation varying from 3.76 to 7.19% from northern temperate regions to warmer southern temperate regions. The carbon budget was constructed using the modelled predictions. Analysis of annual net production and fluxes showed that irrespective of the varying climatic conditions, the percentage of annual fluxes of an event, as a proportion of the total photosynthetic production remained almost same. The respiration of shoots, as well as rhizomes and roots, was shown to consume a considerable amount of photosynthetic production: 25% by shoot respiration and 40% by rhizome and root respiration.