Abstract
To clarify the distribution of radioactive contamination in bed logs, which can transfer to shiitake (Lentinula edodes) fruiting bodies, the concentration of radioactive cesium (Cs) in the trunks of konara oak (Quercus serrata) trees was measured in 10-year-old stands emerging after the Fukushima nuclear accident. While the ratio of Cs concentration (per kg) in bark and stem wood was 1.9 : 1, the overall quantity in bark was 26% of total Cs, due to the relative contributions of bark and wood to trunk weight. This result differed significantly from the distribution of radioactive contamination in standing trees directly affected by the fallout. Disc samples taken from trees at a height of 1 to 3 m revealed that the concentration of radioactive Cs in both the bark and wood tended to be higher at 1 m. On the other hand, in determining correlations in Cs between the trunk (disc) and branch, bark or wood, the highest correlation was found between trunk and wood (R2 = 0.875). These results indicated that an evaluation method using the wood of logs below 1 m of standing trees is effective as a simple inspection method for stands of trees that emerged after the nuclear accident, which are to be used for bed log cultivation of shiitake mushrooms.
