Further threat ,expansion of distribution of Hydrocotyle ranunculoides and Alternanthera philoxeroides ,

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K00647
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Environmental and ecological symbiosis
• Research Institution: Kumamoto University
• Principal Investigator: MINAGAWA Tomoko 熊本大学, 大学院先端科学研究部(工), 准教授 (10355828)
• Co-Investigator(Kenkyū-buntansha): 鬼倉 徳雄 九州大学, 農学研究院, 准教授 (50403936)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 特定外来生物 / ナガエツルノゲイトウ / ブラジルチドメグサ / 多様性 / 魚類 / 影響 / 対策

Outline of Final Research Achievements

This study evaluated the distribution characteristics, distribution factors, and impacts on biodiversity of Hydrocotyle ranunculoides and Alternanthera philoxeroides, which are invasive alien species. In the Kikuchi River, it was shown that weirs were involved in the expansion of the distribution of Hydrocotyle ranunculoides, and that the distribution of A. philoxeroides was related to the bank slope, friction velocity, and soil moisture. We also quantitatively clarified that A. philoxeroides is the most dangerous species that is superior not only to native species but also to competition with other invasive alien species. Furthermore, it was shown that the overgrowth of A. philoxeroides and Pistia stratiotes contributed to the reduction of fish diversity. Based on these results, the points to be noted when excavating the flood channel and creating the artificial backwaters for flood plain ecosystem conservation were shown.

Free Research Field

河川生態工学

Academic Significance and Societal Importance of the Research Achievements

本研究は複数の外来種が在来の氾濫原依存種の減少や氾濫原生態系の変質を加速化させている現象を氾濫原生態系に対するさらなる脅威として位置づけ、ブラジルチドメグサとナガエツルノゲイトウに着目し、分布特性や拡大要因を、水理諸量、河川構造物、河岸形状などの要因を含め明らかにした。また、高水敷掘削などの人為的な改変との関連性を踏まえ、具体的な対策を提示した。これらの結果は、生態学、応用生態工学、河川工学領域への学術的な貢献と技術的な貢献が期待でき、日本における生物多様性の保全に寄与するものである。