其他摘要：This study aimed to alleviate radiocesium pollution in Lentinula edodes (shiitake mushrooms) by using the bed-log cultivation method. In 2013, we set bed logs on the surface of A-horizon soil where A0 layer was removed in 2012 in a forest located in Iwate Prefecture, Japan. Radiocesium concentrations or amounts of the treated plots were compared with those of non-treated plots for 5 years. In 2017, mean radiocesium concentration in bed logs collected from treated plots was 68％ of that in bed logs collected from non-treated plots. Radiocesium concentration was also reduced in fruiting bodies from treated plots. Radiocesium amount in A0 layer decreased after the removal of A0 layer, and this trend continued for at least 5 years, despite the supply of radiocesium from the canopy layer as litter. Radiocesium concentration in A0 layer of treated plots was 46％ of that in non-treated plots in 2017. These results indicated the successful alleviation of radiocesium pollution in bed-log-cultivated L. edodes. However, 4 years after treatment, radiocesium amount in A-horizon soil (0-5 cm in depth) exceeded that of A0 layer. Additionally, direct accumulation of radiocesium in A-horizon soil via L. edodes hyphae or adhesion onto bed logs due to rain splash is a matter of concern. Thus, currently, there is a risk of increased radiocesium pollution when the bed log is set directly on A-horizon soil.
