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研究課題 | Project

多摩川中流部における樹林伐根跡地の植生変化と立地との関係
Regenerated vegetation and stand conditions in denuded area by destruction of alien invasive species forests in the middle reach of the Tama-gawa River.

学術研究
Academic
Research
No.330
代表研究者
Principal
Investigator
和田 美貴代
Mikiyo Wada
所属(当時) 熊本大学薬学部 准教授
Kumamoto University School of Pharmacy Department of Medicinal Plant Research Associate Professor
研究内容要約
Research
Summary

多摩川中流部の四谷本宿床止から浅川合流点間の右岸の河川敷において、礫河原自然再生事業の一環として行われた北米原産のハリエンジュ林と中国原産のニワウルシ林の伐根跡地およびにシバ草地の表土剥ぎ取り跡地に再生してくる植物種を4年間にわたりモニタリングした。また地形と堆積物およびに土壌水分の調査を行い再生植生との関係を検討した。その結果、外来樹種の伐根跡地に、土壌粒径組成や土壌水分条件の違いに応じて異なる礫河原植物が侵入することが分かった。すなわち、カワラケツメイ、カワラサイコ、カワラヨモギは堆積物が細粒で土壌水分条件のよい地点に、マルバヤハズソウ、ヤハズソウは堆積物が粗粒で土壌水分含有量が比較的低い地点に生育が確認された。一方で、ハリエンジュやニワウルシも、伐根に際し地中に残存した根から根萌芽で再生し、とくに土壌水分条件の良い立地で旺盛な成長を見せた。礫河原植物は木本種やクズなどの成長に伴って被度が低下しことから、それらを定着させるためには木本種やクズなどを積極的に除去していく必要があるといえる。



In the middle reach of the Tama-gawa River, on the right bank of floodplain between Yotuya-Honsyuku Ground sill and the confluence of the Tama-gawa River and the Asa-kawa River, forests of alien invasive species such as Robinia pseudoacacia (originally come from North America) or Ailanthus altissima (originally come from China) were destructed as a part of natural restoration project on the gravel riverbed vegetation. In the barren area emerged by grubbing trees, we monitored regenerating vegetation for 4 years. We also investigated relief features, sediment deposit and soil moisture to clarify relationship between regenerating vegetation and environmental factors. Some plants typical of gravel riverbed vegetation, such as Chamaecrista nomame, Potentilla chinensis, and Artemisia capillaris were colonization in the area with fine sediment and relatively high soil moisture, whereas Lespedeza striata and L. stipulacea were recruited in the area with coarse sediment and relatively low soil moisture. R. pseudoacacia and Ailanthus altissima regenerated by sprouting from roots that were remained in the ground after tree grubbing, and they showed quick‐growing in the area where soil moisture condition was relatively high. The coverage of gravel riverbed vegetation decreased with the increase of coverage of the alien tree species and Pueraria montana var. lobate, indicating that extermination of these alien trees and climber are necessary to establish gravel riverbed vegetation.


共同研究者
Collaborators

長岡 総子

奥田 重俊



Fusako Nagaoka

Shigetoshi Okuda


研究全文
Full Text