No.261 研究課題 / Project
多摩川中流域における河川敷植生の復元と管理についての研究A Study of restoration and management of the floodplain vegetation in the Middlecourse of the Tama River| 学術研究 Academic Research |
No.261 |
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| 代表研究者 Principal Investigator |
一澤 麻子 Asako Ichisawa |
| 所属（採択当時） Affiliation |
横浜植生研究会 会員 Yokohama Vegetation Society member of Yokohama Vegetation Society |
| 研究内容要約 Research Summary |
より自然に近い礫河原植生の再生に必要な知見を得るため、多摩川永田地区の造成礫河原に成立した植生について、自然の礫河原植生の種組成との比較、造成後4年間に作成された植生図の数値地図化による植生変化の解明、さらに植生と地形、表層砂礫、土壌、管理方法との関係の解析を行った。 造成礫河原と自然の礫河原で共通した礫河原植生は先駆的な特徴をもつ群落のみであった。 造成礫河原の植生変化と地形との関係から河原の一・二年生草本群落が存続するためには出水の際に冠水するが砂が堆積しない環境が必要と分かった。ただし、礫河原植生の存続には地形に加え表層堆積物などの条件も重要と考えられた。 造成礫河原の植生と表層砂礫や土壌条件、冠水状況、管理などとの関係を解析した結果、カワラノギクが生育しうるような礫河原植生が存続するには、表層の礫が浮石状態か細粒物質によって充填されていない状態で、表層下部に堅固な礫層が存在する必要があることが明らかになった。 以上の結果により礫河原植生を再生するための指針を提言した。 To restore the natural vegetation on artificial gravel bar, a study about the vegetation established in the artificial gravel bar at Nagata area, the middle reach of the Tama River has been conducted. At first, a comparison of the species composition was made between the vegetation of natural and artificial gravel bars. Phytosociological study revealed that the vegetation on the artificial gravel bar was different form that of natural gravel bar except for annual and biennial herb communities. Next, the relationship between vegetation change and topography on artificial gravel bar was analyzed by GIS method using vegetation maps. The results suggest that floodings without sand deposits are needed for persistence of the annual and biennial herb communities, which are distributed mainly on floodplains. The factors controlling rates of plant succession are considered to be frequency of flooding, topography and surface deposits. From these results, it is concluded that creating surface sediment conditions and topography of artificial gravel bars are needed for the recovery of persistent floodplain vegetation. Thirdly, the relationship between recovered vegetation type and surface sedimentary structures was clarified, followed by the analysis on the relationship between established vegetation type and vegetation management. The results suggest that soil condition of Kummerowia stipulacea type is the same as the habitat of Aster kantoensis. This type grows both on the non-matrix-filled surface composed of open-work gravels and on the topsoil which contains relatively high amounts of clay and silt. Taking every factor into consideration, we proposed guidelines for restoration of natural vegetation on artificial gravel bar. |
| 共同研究者 Collaborators |
長岡総子（横浜植生研究会）・畠瀬頼子（財団法人 自然環境研究センター）和田美貴代（東京大学理学系研究院）阿部聖哉（財団法人 電力中央研究所）・奥田重俊（株式会社建設環境研究所） Fusako Nagaoka（Yokohama Vegetation Society）Yoriko Hatase(Japan Wildlife Research Center)Mikiyo Wada(School of Science, The university of Tokyo )Seiya Abe(Central Research Institute of Electric Power Industry)Shigetoshi Okuda( Civil Engineering and Eco-Technology Consultants Co. Ltd.) |
| 研究全文 Full Text |
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