Temporal changes of air dose among different types of forests

The spatially heterogeneous at the initial contaminations in a local scale and the temporal changes of the contaminations were investigated by the air dose rate changes among three types of forest stands (5 seed orchards, 24 Japanese red pine and deciduous hardwood forests, 13 Japanese cedar forests) at the height of 1 m and 10 cm from June, 2011 to June 2015 in Koriyama city, Fukushima Prefecture. In June, 2011, the air dose rates were associated with the vegetation types (seed orchards > Japanese red pine and deciduous hardwood forest > Japanese cedar forest). Therefore, it was suggested that the air dose rates influenced by the canopy interceptions during the initial atmospheric fallout. In 2015, the air dose rates were spatially homogeneous, however, the time-depended changes of air dose rates varied among three types of the forests from 2011 to 2014, the decrease rate of air dose was in the order of seed orchards, the Japanese red pine and deciduous hardwood forests and the Japanese cedar forests. (author)