パラオ諸島における分布予測モデルを用いたマングローブ生育地の脆弱度評価

概要

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Influence of hydraulic conditions on the regeneration of mangrove forest was clarified at the Okukubi River in Okinawa Island, Japan. Field surveys for identifying structure of mangrove forest were conducted at 8 plots, where Bruguiera gymnorrhiza (L.) LAM. and Kandelia candel (L.) DRUCE. dominate. While bed-level variation, absolute bed-level fluctuation and non-dimensional shear stress during a flood were estimated by two-dimensional bed deformation analysis. Then relationship between density of seedlings and saplings of mangrove species and hydraulic conditions was evaluated from regression analysis. The density of maturing trees of mangrove species positively correlates with absolute bed-level fluctuation and non-dimensional shear stress. The result represents that regeneration of mangrove community is occurred at sites where sediments of bar surface is exchanged during the flood. Soft soil, which is easy to stick for mangrove seeds, is needed as the first stage of regeneration, and hence sediment movement is essential for forming regeneration site of the mangrove species.
土木学会の論文