PROBLEM TO BE SOLVED: To improve a water quality improving effect of a vegetated floating island by protecting rhizomes of aquatic plants planted on a vegetation base from feeding damage caused by feeding organisms.SOLUTION: The vegetated floating island 11 includes the vegetation base 12 on which emergent plants 21 are planted and a float 13, and is floated in a closed water area 14. The vegetation base 12 is composed of a three-dimensional net structure such as a fibrous structure or porous structure. A protection net 31 structured as a net basket is attached with a frame 32 to the bottom of the vegetation base 12, and the rhizomes 21b of the emergent plants 21 extending downward through the vegetation base 12 from the bottom of the vegetation base 12 are protected from the feeding damage caused by feeding organisms 22 by covering the rhizomes with the protection net 31. With this structure, growth of the rhizomes 21b of the emergent plants 21 is facilitated, and the amount of release of allelopathic substances from the rhizomes 21b is increased, so that the water quality improving effect of the vegetated floating island 11 can be enhanced.COPYRIGHT: (C)2012,JPO&INPIT【課題】植生基盤に植栽された水生植物の根茎を食害生物の食害から保護して、植生浮島の水質改善効果を高めることである。【解決手段】抽水植物21が植栽される植生基盤12とフロート13とを備えて閉鎖性水域14に浮かべられる植生浮島11において、植生基盤12を繊維質構造体や多孔質構造体等の三次元網目構造体で構成する。植生基盤12の底面にフレーム32によりネット籠として構成された保護ネット31を取り付け、植生基盤12を貫通して当該植生基盤12の底面から下方に向けて伸長する抽水植物21の根茎21bを、この保護ネット31により覆って食害生物22の食害から保護する。これにより、抽水植物21の根茎21bの発達が促進され、根茎21bからのアレロパシー物質の放出量が増加して植生浮島11の水質改善効果が高められる。【選択図】図1
