Example of Application on Riparian Revegetation in Neo- Tural River Reconstruction, and Evaluation After Several Years

27 Mar Example of Application on Riparian Revegetation in Neo- Tural River Reconstruction, and Evaluation After Several Years

View Original

Abstract

ツルヨシとカサスゲを用いて水辺緑化を行った事例をもとに，水辺エコトーンの状況調査を行った．その結果，以下の点が明らかになった． (1)水辺緑化を行なった場所においては，植栽した植物が優占し，水域にある程度の範囲で張り出すことで，水際域の流速を弱める等，多様な水辺環境の創出に寄与した． (2)ツルヨシは，流れに匍匐茎を流すように広がり，水際域に進出しやすい特性を持つ．ツルヨシが定着した後は，それを被圧する植物の侵入はほとんど見られず，安定した群落を形成するが，草丈が2mに達して人の視界を遮る． (3)カサスゲはツルヨシに比べて抽水状態での生育範囲は狭いものの，流れのある条件においても水際域への進出が見られ，視界を遮らない草高の植生護岸を形成した． (4)植生ロールを用いた事例では，植生基盤であるヤシ繊維が劣化する前に目的とする植物群落を形成させる必要がある．特に，植物が水域側に進出することが，水辺環境を多様化する上で重要である．そのためにはツルヨシやカサスゲのような水域に進出可能な多年草の植栽が必要である．

English Abstract

Based on data for riparian revegetation for Phragmites japonica and Carex dispalata, a situation was surveyed in which ecotones ware formed. In place with riparian revegetation, the planted species were domi nt and spreaded in the water area, which contributed to creation of a diverse riparian environment, for instance by decreasing the flow velocity in the riparian area. Phragmites japonica grew runners and spreaded throughout the growth area. It readily creates riparian ecotones, even in rapids. However, in some cases, the plant grows as high as 2m, which obstructs view and undesirable from a landscape point of view. In the cases in Carex dispalata, which does not obstruct view, was used, vegetated bank protection was formed in the stream. The growth area of Carex dispalata is smaller when the roots are in the water and stems of the plants are above the water. However, it is expected to function as a riparian ecotone. When using a coconut fiber roll, vegetation bank protection must form before the coconut fiber deteriorates. It is important that planted plants advances to a water side, especially to diversify the waterside environment. For the reason, Phragmites japonica and Carex dispalata, a perennial plant which can advance to a water areas, must be planted.