Radioactivity Dynamics in forests
（2024）
ＱHow is it considered that radioactive cesium-137 (137Cs) concentrations on the forest surface (forest floor) in Fukushima prefecture will change in the future?
ＡIt became clear that 137Cs concentrations in the organic layer of the forest floor have been decreasing rapidly since the accident, but meanwhile the decreasing trend is dependent on vegetation differences and mean annual temperature. A decline in the decrease speed was observed, particularly in deciduous broad-leaved forests and cool high-altitude areas, suggesting a possibility that 137Cs concentrations tend to remain relatively high.
A study team of the National Institute for Environmental Studies and Forestry and Forest Products Research Institute used a mathematical model called the radioecological model “FoRothCs” to extensively estimate changes over 20 years in the radioactive cesium-137 (137Cs) concentrations in the organized layers, such as fallen leaves accumulated on the forest surface (forest floor) of the entire Fukushima prefecture under the influence of the Fukushima Daiichi nuclear power plant accident. This was done by dividing the forests into evergreen conifer forests and deciduous broad-leaved forests for the first time in Japan.
The result revealed that while 137Cs concentrations in the organic layer of the forest floor had been promptly decreasing since the accident, the decrease trend was dependent on differences in vegetation and mean annual temperature. A decline in the decrease speed was confirmed particularly in the deciduous broad-leaved forests and cool high-altitude areas, suggesting a possibility that 137Cs concentrations tend to remain relatively high.
It is expected that this result will be applied for more accurate assessment of 137Cs contamination in the forest ecosystem and for efficient contamination management in the river basin ecosystem under that impact.
Figure Estimation results of 137Cs concentrations in the organic layer of the forest floor by FoRothCs model
(Research findings of the National Institute for Environmental Studies. Reproduced (partly edited) from the website of the National Institute for Environmental Studies)
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