Japanese Mangroves as Blue Carbon Ecosystems

In Japan, there are 885 ha of valuable mangrove forests as the northern limit of their distribution in the Pacific Ocean, 604 ha of which are distributed in Iriomote Island in the Yaeyama Islands. The maximum aboveground biomass in Iriomote was estimated to be 361 Mg ha−1 for Bruguiera gymnorrhiza community. The accretion rate of aboveground biomass is considerably slower than in the tropics, which is largely due to the frequent and intense typhoons in addition to climatic conditions. On the other hand, belowground, Rhizophora stylosa communities accumulate mangrove peat and store approximately 500 Mg ha−1 of carbon up to 1 m deep, as in the tropics. Although the fine-root production, the main parent material of mangrove peat, is inferior to that in the tropics, it can be evaluated that the belowground plays a significant role as a place of carbon storage.