Abstract
In contaminated forest, it is essential to measure the temporal variation of air dose rate because forests constitute a major part of the land use in the contaminated area by Fukushima Daiichi nuclear power plant accident. In this study, we examined the temporal variation of air dose rate from 2011 to 2014 at heights 1 m and 10 cm at Japanese cedar（Cryptomeria japonica D. Don）man-made forests and the deciduous broad-leaved forest in Kawauchi-mura, Otama-mura, and Tadamimachi at Fukushima Prefecture. In addition, we examined the relationship between radioactive cesium migration from canopy to forest floor and air dose rate. From 2011 to 2012, the decrease of air dose rate was low compared with that estimated by radioactive cesium natural decay in the forests. We considered the reason why much of radioactive cesium moved from canopy to forest floor. After 2012, the air dose rate had reduced with natural decay at the forest stands, which indicated that the extent of radioactive cesium migration was very low after 2012. Therefore, we considered that the resumption due to the weathering effect was small in the forest ecosystem.
