Scenarios for modeling radiocesium dynamics in forests in the Fukushima area: datasets for Japanese cedar and deciduous broad-leaved forests

We have compiled a dataset of radiocesium (137Cs) activity concentrations and 137Cs inventories in forests affected by the Fukushima Daiichi Nuclear Power Plant accident, based on data published in peer-reviewed international journals by the research group at the Forestry and Forest Products Research Institute as of April 2025. The above-ground compartments include needles/leaves, branches, bark, sapwood, and heartwood, while the below-ground compartments consist of the organic horizon and the mineral soil horizon (0–20 cm, sampled in 5 cm increments). The dataset covers the period from 2011 to 2020 and includes data from a Japanese cedar (Cryptomeria japonica) forest in Otama Village (Scenario A) and a deciduous broad-leaved forest dominated by konara oak (Quercus serrata) in Kawauchi Village (Scenario B). The two scenarios include the following information: (1) geographical location, (2) source term, (3) climate characteristics, (4) soil characteristics, (5) tree characteristics, (6) field data used to calculate the 137Cs distribution in the forest, and (7) ambient dose equivalent rates. Data from Scenario B were previously used in model comparisons (Hashimoto et al., 2021). We plan to incorporate data published in peer-reviewed international journals after May 2025 in future updates. Version 1-0 The published papers on which this database is based are as follows: Fujii et al. (2014) Vertical migration of radiocesium and clay mineral composition in five forest soils contaminated by the Fukushima nuclear accident. Soil Science and Plant Nutrition 60(6), 751–764. https://doi.org/10.1080/00380768.2014.926781. Imamura et al. (2015) Change of air dose rate in forests from 2011 to 2014 after the Fukushima Daiichi nuclear power plant accident. Japanese Journal of Forest Environment 57(2), 101–107. https://www.jstage.jst.go.jp/article/jjfe/57/2/57_101/_article/-char/en. Imamura et al. (2017) Temporal changes in the radiocesium distribution in forests over the five years after the Fukushima Daiichi Nuclear Power Plant accident. Scientific Reports 7, 8179. https://doi.org/10.1038/s41598-017-08261-x. Kenzo et al. (2020) Vertical distribution of radiocesium concentrations among crown positions and year-to-year variation in four major tree species after the Fukushima Daiichi Nuclear Power Plant accident. Journal of Environmental Radioactivity 225, 106447. https://doi.org/10.1016/j.jenvrad.2020.106447. Komatsu et al. (2016) Characteristics of initial deposition and behavior of radiocesium in forest ecosystems of different locations and species affected by the Fukushima Daiichi Nuclear Power Plant accident. Journal of Environmental Radioactivity 161, 2–10. https://doi.org/10.1016/j.jenvrad.2015.09.016. Malins et al. (2021) Calculations for ambient dose equivalent rates in nine forests in eastern Japan from 134Cs and 137Cs radioactivity measurements. Journal of Environmental Radioactivity 226, 106456. https://doi.org/10.1016/j.jenvrad.2020.106456. Manaka et al. (2019) Six-year trends in exchangeable radiocesium in Fukushima forest soils. Journal of Environmental Radioactivity 203, 84–92. https://doi.org/10.1016/j.jenvrad.2019.02.014. Manaka et al. (2022) Ten-year trends in vertical distribution of radiocesium in Fukushima forest soils, Japan. Journal of Environmental Radioactivity 251–252, 106967. https://doi.org/10.1016/j.jenvrad.2022.106967. Nagakura et al. (2016) Cesium, rubidium and potassium content in the needles and wood of Japanese cedar trees harvested from the sites of different radiocesium deposition levels. Japanese Journal of Forest Environment 58(2), 51–59. https://www.jstage.jst.go.jp/article/jjfe/58/2/58_51/_article/-char/en. Ohashi et al. (2017) Temporal trends in 137Cs concentrations in the bark, sapwood, heartwood, and whole wood of four tree species in Japanese forests from 2011 to 2016. Journal of Environmental Radioactivity 178, 335–342. https://doi.org/10.1016/j.jenvrad.2017.09.008. Ohashi et al. (2022) Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident. Scientific Reports 12, 11243. https://doi.org/10.1038/s41598-022-14576-1. Description of the dataset: Komatsu et al. (2025) Data-driven scenarios for modeling radiocesium (137Cs) behavior in forests affected by the Fukushima nuclear accident. Journal of Forest Research, 1–4. https://doi.org/10.1080/13416979.2025.2582954 Acknowledgements: We would like to express our sincere gratitude to the International Atomic Energy Agency (IAEA) and its Methods for Radiological and Environmental Impact Assessment (MEREIA) program for providing us with the opportunity to compile this dataset. We are also thankful to the Kanto Regional Forest Office of the Forestry Agency and the Kawauchi Village Office for granting permissions to conduct our observation of 137Cs distribution in the forest ecosystem. Funding: This study was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI, Grant Numbers 16H04945 and 25K02067; by the Forestry Agency of Japan through the project titled “Surveys on Radioactive Cesium Distribution in Forests”; and by a grant from the Forestry and Forest Products Research Institute (Grant #201126). Reference: Hashimoto et al. (2021) Dynamics of radiocaesium within forests in Fukushima—results and analysis of a model inter-comparison. Journal of Environmental Radioactivity 238–239, 106721. https://doi.org/10.1016/j.jenvrad.2021.106721.