Radiocesium distribution and changes of the wood in sugi and hinoki caused by the accident of Fukushima Daiichi Nuclear Power Plant

In order to reconstruct the forestry in Fukushima, we have studied the situation of radioactive contamination in the wood of the trees. To clarify the radiocesium contamination mechanism, Sugi (Japanese cedar, Cryptomeria japonica) and Hinoki (Japanese cypress, Chamaecyparis obtusa) trees were compared. In 3 forest sites, where Sugi and Hinoki were closely planted, the radial and vertical radiocesium distribution and changes from 2012 to 2014 were studied. As a results, the radiocesium concentration in heartwood of Sugi were higher than that of Hinoki, although that of sapwood was almost same in both tree species. It indicated that Radiocesium tended to accumulate in heartwood in Sugi compared to that in Hinoki. And Radiocesium in heartwood of Sugi increased from 2012 to 2014. The radiocesium concentration in heartwood of Sugi showed a good relationship with the water content in Sugi, and the water content in Sugi were almost higher than that of Hinoki. It indicated the radiocesium in sapwood moved more easily than that in heartwood as increasing the water content in heartwood. There were possibility that the differences of the water content in heartwood caused that of the radiocesium distribution in heartwood between Sugi and Hinoki. (author)