1997 Fiscal Year Final Research Report Summary
Chronological Study on Forested Watershed Changes due to sediment movement by forest age analysis
| Project/Area Number |
08456072
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
林学
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
ARAYA Tohru HOKKAIDO UNIV., FAC.OF AGR., PRO., 農学部, 教授 (00001462)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUCHI Shunichi HOKKAIDO UNIV., FAC.OF AGR., ASSI.PRO., 農学部, 助手 (10250490)
SHIMIZU Osamu HOKKAIDO UNIV., FAC.OF AGR., ASSI.PRO, 農学部, 助手 (20178966)
YAJIMA Takshi HOKKAIDO UNIV., FAC.OF AGR., ASSO.PRO., 農学部, 助教授 (90142702)
NAKAMURA Futoshi HOKKAIDO UNIV., FAC.OF AGR., ASSO.PRO., 農学部, 助教授 (90172436)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Riparian forest / Forset stand / Forest age distribution / Tree rings / Adventitious roots / Volcanic ash / Volcanic mudflow / Sedimentary deposit |
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| Research Abstract |
Chronological analysis of geomorphic surfaces using forest ages, radiocarbon dates or tephra dates is an effective method for investigating geomorphic history of watersheds, and even for understanding spatial and temporal characteristics of sediment movement processes within the watersheds. Summarized results of this study are as follows : 1) We examined sediment routing in the Saru River basin. Tephrochronological analysis of hil1slopes showed long-term rates of sediment production caused by landslides. Volume of reservoir sedimentation and age distribution of forests established on sediment in the reservoirs were analyzed, indicating sediment yields from upstream basins. 2) Regeneration dynamics of riparian forests were examined along the Tokachi River. Analysis of species composition and tree age structure of the riparian forests revealed that the magnitude of sediment movement associated with flood events controlled the extent of disturbance and regeneration of riparian forests, creating a mosaic distributional pattern of forest patches in the riparian zone. 3) Debris flow history was researched at the alluvial fan head on Rishiri Island. Tree-ring chronology obtained from living trees was used to cross-date the establishment and death of the trees which were buried by debris flows of indeterminate ages. Results indicated two clusters of the debris-flow dates in the 1870s and the early l950s. 4) Radiocarbon dates and stratigraphic analysis of volcanic mudflow deposits provided new findings of mudflow occurrences in Mount Tokachi Volcano and Mount Meakan Volcano.
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