CHARACTERISTICS OF THE CLAY-HUMUS COMPLEXES IN MANGROVE SURFACE SOILS

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Characteristics of clay-humus complexes in mangrove surface soils along a mangrove creek in Fukido river, Ishigaki island, Okinawa were investigated under this study. Six locations from the lower site to upper site in the river were selected, and surface soils (0.5 cm thick) were collected at two different sides of the bank and the forest. The degree of humification of NaOH soluble (NaOH-HA) and Na_4P_2O_7 soluble (Na_4P_2O_7-HA) humic acids of mangrove surface soils were Rp and B types, respectively. The degree of humification of humic acids was gradual degradation from upper to lower sites in the mangrove forest. Humic substances were accumulated in larger quantities in surface soils while are closer to waterside of the bank and were tended to sediment in larger quantities at about 220 m from downstream in the mangrove forest. Contents of clay minerals (Kaolinite, Illite, Vermiculite and Vermiculite-Chlorite integrade), extracted bases (Na, K, Mg and Ca) and metals (Fe and Al) in humic substances showed a similar accumulating tendency to the humic substances. It can be concluded that the clay-humus complexes were formed with clay minerals, metals and bases in mangrove surface soils. It was apparent the complexes were accumulated in mangrove surface soils, based on the characteristics of the topography.
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