A Study on Ma Gement by Cutting of the Embankment Vegetation

27 Mar A Study on Ma Gement by Cutting of the Embankment Vegetation

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Abstract

河川堤防植生 (河川堤防法面上の植生) の実態を明らかにし植生管理手法を確立するために, 高知県仁淀川, 兵庫県猪名川, 徳島県那賀川の堤防法面で植生と刈り取り頻度との関係について調査を行つた。両者の関係については, 刈り取り頻度が2年に1回以下の低頻度ではススキが, 年1, 2回ではチガヤやススキが, 年3回ではシバがそれぞれ優占し, また刈り取り頻度に対応して草丈の増減, 季節性の有無, 種多様性の高低が生じることが認められた。この内堤防管理の安全性および景観性, 種多様性などの環境機能についての条件を勘案すると, 堤防植生としてはチガヤ型がふさわしくその管理方法としては年2回の刈り取りを行うのが望ましいと考えられる。

English Abstract

In order to clarify the effects of cutting on growth, the number of species, species diversity and life-form of the embankment grassland domi ted by Miscanthus sinensis or Imperata cylindrica var. hoenigii, field experiments were conducted on grassland community on slope of embankment at the Niyodo river in Kochi Pref., the I river in Hyogo Pref. and the ka river in Tokushima Pref. We set four plots based on the cutting frequency in each study site. Each plot contained five quadrats.
In the plots of no cutting and those of one cutting every two years, Imperata cylindrica var. koenigii progressively decreased and Miscanthus sinensis mostly domi ted. In the plots of one or two cuttings per year, Imperata cylindrica var. hoenigii or Miscanthus sinensis domi ted. In the plots of three cuttings per year, Zoysia japonica domi ted.
It was observed that the number of species and species diversity were highest in the plot of two cuttings per year. It seemed that the community domi ted by Imperata cylindrica var. koenigii, that was cut two times per year, was available as soil-binder on embankment slopes and as grassland biotope.