Estimating cesium absorption through tree fine roots by using in-growth core method

Radioactive materials were released to the environment due to the Fukushima Dai-ichi Nuclear Power Plant accident in March of 2011. It is important for us to understand the dynamics of radioactive cesium (137Cs) in forest because it covers large area of Japan. Trees are one of the main composition of forest and affect on the dynamics of radioactive cesium in forest so it is also important to measure the translocation of cesium from the soil to the trees. To measure the translocation of 137Cs from the soil to the tree fine roots, we applied in-growth core method that was usually used to measure the biomass of roots. We prepared two different types of soils, one with 137Cs and the other without 137Cs, and set into the In-growth core for each soils. We buried In-growth core for two times changing the starting season (1. from June 2013 to June 2014, 2. from December 2014 to November 2015). We found positive correlation between the 137Cs concentration of the soils and the tree fine roots collected in 2014. On the other hand, there were no relationship between the 137Cs concentration of the soils and the tree fine roots collected in 2015. These results indicated that tree fine roots absorbed 137Cs from the soils but there were some other factors that affected on the absorption of tree fine roots (e. g. seasons we collected the In-growth core). (author)