title: 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.
abstract: After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, information about stand-level spatial patterns of radiocesium initially deposited in the surrounding forests was essential for predicting the future dynamics of radiocesium and suggesting a management plan for contaminated forests. In the first summer (approximately 6 months after the accident), we separately estimated the amounts of radiocesium ((134)Cs and (137)Cs; Bq m(-2)) in the major components (trees, organic layers, and soils) in forests of three sites with different contamination levels. For a Japanese cedar (Cryptomeria japonica) forest studied at each of the three sites, the radiocesium concentration greatly differed among the components, with the needle and organic layer having the highest concentrations. For these cedar forests, the proportion of the (137)Cs stock in the aboveground tree biomass varied from 22% to 44% of the total (137)Cs stock; it was 44% in highly contaminated sites (7.0 × 10(5) Bq m(-2)) but reduced to 22% in less contaminated sites (1.1 × 10(4) Bq m(-2)). In the intermediate contaminated site (5.0-5.8 × 10(4) Bq m(-2)), 34% of radiocesium was observed in the aboveground tree biomass of the Japanese cedar stand. However, this proportion was considerably smaller (18-19%) in the nearby mixed forests of the Japanese red pine (Pinus densiflora) and deciduous broad-leaved trees. Non-negligible amounts of (134)Cs and (137)Cs were detected in both the sapwood and heartwood of all the studied tree species. This finding suggested that the uptake or translocation of radiocesium had already started within 6 months after the accident. The belowground compartments were mostly present in the organic layer and the uppermost (0-5 cm deep) mineral soil layer at all the study sites. We discussed the initial transfer process of radiocesium deposited in the forest and inferred that the type of initial deposition (i.e., dry versus wet radiocesium deposition), the amount of rainfall after the accident, and the leaf biomass by the tree species may influence differences in the spatial pattern of radiocesium by study plots. The results of the present study and further studies of the spatial pattern of radiocesium are important for modeling future radiocesium distribution in contaminated forest ecosystems.
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: kopine@ffpri.affrc.go.jp.
authors.forename: Masabumi
authors.initials: M
authors.lastname: Komatsu
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kaneko
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Shinta
authors.initials: S
authors.lastname: Ohashi
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Katsushi
authors.initials: K
authors.lastname: Kuroda
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Department of Environment and Energy, Tohoku Institute of Technology, 35-1 Yagiyamakasumi-cho, Taihaku-ku, Sendai, Miyagi 982-8577, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sano
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Shigeto
authors.initials: S
authors.lastname: Ikeda
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Saito
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kiyono
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Shikoku Research Center, Forestry and Forest Products Research Institute, 2-915 Asakuranishimachi, Kochi, Kochi 780-8077, Japan.
authors.forename: Mario
authors.initials: M
authors.lastname: Tonosaki
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan; Laboratory of Radioplant Physiology, the University of Tokyo, 1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Miura
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Akama
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kajimoto
authors.affiliation: Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Takahashi
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D032485:Cryptomeria; D065928:Forests; D062406:Fukushima Nuclear Accident; D007564:Japan; D028223:Pinus; D018515:Plant Leaves / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D029963:Quercus; D011834:Radiation Monitoring; D011848:Radioactive Pollutants / Q000032:analysis*; D014934:Wood / Q000737:chemistry
chemical_list: D002588:Cesium Radioisotopes; D011848:Radioactive Pollutants
keywords: Forest ecosystems; Initial deposition; Radiocesium; Stock