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Ministry of Agriculture, Forestry and Fisheries

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Regeneration of Forests and Forestry

Comprehensive summary

The impacts of radioactive substances are still under various ongoing investigations, including monitoring by national and prefectural governments and the Forestry and Forest Products Research Institute.

The Forestry Agency edited and published this booklet as a comprehensive summary of the current status of radioactive substances in forests, and of the impact of such substances on timber, mushrooms, and other forest products.

Surveys on Radioactive Cesium Distribution in Forests    NEWアイコン

Survey 1

[Background and Objective]

In 2011, the Forestry Agency set monitoring sites in three municipalities (Kawauchi Village, Otama Village, and Tadami Town) in Fukushima Prefecture in order to clarify the distribution of radioactive cesium within forests. Since then, the Agency has investigated the concentrations and accumulated quantities of radioactive cesium in soil, fallen leaves, and sections of trees such as leaves and trunks, and published the results. In response to a decrease in radioactive cesium concentrations and the lifting of areas under evacuation orders, the Agency reviewed the monitoring sites and added some sites in FY2017. From July to September 2019, the Agency surveyed the concentrations and accumulated quantities of radioactive cesium for six forests at 4 monitoring sites in 2 villages, for which the Agency is reporting the results.

Survey 2

[Purpose of Survey]

The past studies on radioactive cesium suggest the total quantities of radioactive cesium accumulated in forests have not changed more than its physical decay, and the amount of release via mountain steam water is infinitesimal. As the majority of radioactive cesium settled in a forest ecosystem remains in the ecosystem, investigation of its dynamics needs to be continuously conducted from a long-term viewpoint. Considering entry into areas with extremely high air dose rates is still restricted, in 2017, the Forestry Agency started surveys to understand the dynamics of radioactive cesium in forests in difficult-to-return and adjacent areas. The results of the FY2019 survey (third year) are shown below.

Survey 3

[Purpose of Survey]

For the concern over re-spreading of fallout radioactive cesium into forests due to cedar pollen scattering, in 2011, the Forestry Agency started a survey to estimate the radioactive cesium concentrations in cedar pollen from male flowers. As a result of past surveys, the radioactive cesium concentrations in male flowers of cedar have shown a general trend of decreasing each year, but they tend to be high when air dose rates are high. This year, continuing from the previous year, the Forestry Agency conducted a survey on radioactive cesium concentrations in male flowers of cedar, especially at sites with relatively high air dose rates.