Effect of floods on the growth of Phragmites japonica on the sediment bar of regulated rivers: a modelling approach

Growth patterns of Phragmites japonica associated with soil characteristics were observed at the sediment bar of the Arakawa River, Japan. Accumulating fine sediments on the bar altered the habitat condition and made it accessible for the growth of P. japonica. The total biomass of the P. japonica shoots was higher in the fine sediments probably due to the better availability of moisture and nutrients. However, the root biomass, particularly the fraction of rhizome, was more abundant in the coarser sediments due to the larger allocation of photosynthates to belowground organs. Such morphological characteristics were found even during the mid-seasonal change in the sediments. The organ-specific growth model was modified to predict the annual growth of P. japonica in different habitats. The translocation rates were provided by functions of the environmental conditions such as habitat grain size. Using the observed environmental data, the growth patterns were simulated with a suitable agreement.