To evaluate distribution in radiocesium among crown positions after accident of Fukushima Dai-ichi Nuclear Power Plant, we collected leaf and branch from upper to lower crown position in four tree species (Chamaecyparis obtusa (Co), Cryptomeria japonica (Cj), Pinus densiflora (Pd), Quercus serrata (Qs)) in 2014, 2015 and 2016 in Fukushima, Japan. We divided those samples into current-year and more than one-year-old (expressed as old leaf and old branch), which sometimes include direct contamination part. Radiocesium (137Cs) concentration was measured for ground samples of leaf and branch by using a germanium semiconductor detector. There were complex differences in 137Cs concentration among species and organ types such as current leaf and old branch between crown positions. In the case of 2016 samples, 137Cs concentration in old branches in Pd and Qs tended to be higher in the lower crown position, but not significant difference was found in current branches and leaves among crown positions. The concentration in branches of Cj were higher in the lower and middle crown positions, but the differences in current leaf concentration were unclear. 137Cs concentration in current leaves in Co were higher in upper crown position, while the concentration in branch and old leaves were lower in the position. Although factors on those differences on interspecific and crown position are unclear, there is a possibility that presence or absence on direct contamination by the accident, and interspecies traits in 137Cs translocation and/or absorption from soil may cause the differences.

05 - Differences in radiocesium concentrations among crown positions in several tree species in Fukushima, Japan.