| Co-Investigator(Kenkyū-buntansha) |
MELANA Emma e. Department of Environment and Natural Resources, Region 7, Philippines, 生態系調査開発部, 調査専門官
TSUDA Satoshi Institute for Basin Ecosystem Studies, Gifu University, 流域環境研究センター, 助教授 (50212056)
FUJIMOTO Kiyoshi Forestry and Forest Products Research Institute, Ministry of Agrivulture, Forest, 森林総合研究所・森林環境部, 研究員
MOCHIDA Yukira Faculty of Science, Tohoku University, 理学部, 助手 (60133047)
MIYAGI Toyohiko Department of Literature, Tohoku Gakuin University, 文学部, 教授 (00137580)
KAWANA Toshio College of Education, University of the Ryukyus, 教育学部, 教授 (60044955)
YAMANAKA Mitsuo Faculty of Science, Kochi University, 理学部, 教授 (50004461)
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| Research Abstract |
Mangrove forests and their habitats were studied on Pohnpei and Kosrae Islands in Micronesia and Cebu and Bohol Islands in the Philippines, to clarify the accumulation process of mangrove peat in relation to sea-level changes. There are two types of peaty habitat in Micronesia : one with thin peat layr about 30-50 cm thick and the other with thick peat layr as thick as 2 m. The former supports a mangrove forest dominated by Sonneratia alba and the latter another mangrove forest characterized by Xylocarpus granatum. The accumulation of mangrove peat is limited to a range corresponding to a part of the intertidal zone because the ground level of mangrove habitats is itself restricted to this range. Consequently, the sea level must rise higher and higher or the level of the land must fall lower and lower for the development of such a thick peat layr as 2 m. In fact, according to the evidences of landforms and C-14 dates, sea level was at the level about 2 m below present one about 1800-2000 yr B.P.Then, it rose to the present level.
The rate of peat accumulation calculated from information obtained from our research was about 2 mm per year. This value does not necessarily indicate the limit of habitat maintenance capability of mangrove forests because it is the average for hundreds or thousands of years and some bigger values within a short period might be included. At least, a mangrove forest is capable of maintaining its own habitat against a sea level rise as rapid as 2 mm per year.
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