河川堤防植生の管理に関する生態学的研究 Ⅲ. 那賀川の堤防植生におよぼす刈り取りの影響

抄録

In order to clarify the effects of cutting frequency on growth, floristic composition, the number of species, species diversity, life-form and biomass of the grassland dominated by Imperata cylindrica var. koenigii on embankments, field experiments were conducted at the Naka river in Tokushima Pref. from 1989 to 1992. Six experimental plots differing in cutting frequency and season were set in the grassland. In the plots of no cutting and one cutting every two years, the coverage of Imperata cylindric avar. koenigi ireduced, three years after experiments had been started. Especially, in the plot of no cutting, the dominant species had changed from Imperata cylindrica var. koenigii to Miscanthus sinensis. In a plot of two cuttings (June, October) per year, the number of species and the species diversity increased. Seasonal change was distinctly recognized in the floristic composition except in plots of no cutting and one cutting every two years. Early-summer aspect was characterized by the appearance of Agropyron tsukushiense var. transiens et al. and the autumn aspect was characterized by the appearance of Setaria glauca et al.