Geochemical evaluation of present mangrove soil in Okinawa Island, Japan

摘要

Mangroves have been stressed by human activities, especially deformation of natural landform and inflow of red soil. Some of the mangroves in the Okinawa Island, Japan, were described with a focus on soil geochemical properties. Soil samples of the common mangrove forests were enriched in heavy metals (such as Zn, Cu and Fe), TS (total sulfur), and P_2O_5 related to organic matter. Soils of dominant biome show normally dark color compared to those of soils affected by red soil inflow. On the other hand, CaO contents became higher in deforested mangrove soils due to its derivation from marine carbonate material. Deforest of mangroves and degradation of their soils were related to the rapid land use and agriculture practices after World War II in the Okinawa Island. Although observation was limited in some areas, contrasting geochemical compositions are significant between common mangrove soils and soils affected by inflow of red soils. Observation of mangrove and geochemical data set are expected to be useful to understand property of red soils and planning of conservation of mangroves.