Keywords:Leachable radiocesium, Stable isotopes, Branchflow, Stemflow, Cedar stand, Oak stand, Bark water storage capacity
This study seeks to better understand the spatial variation in the transport and deposition of radiocesium through the tree canopy via branchflow and stemflow in the aftermath of the Fukushima Dai-ichi Nuclear Power Plant accident. Working in both a coniferous forest (Cryptomeria japonica, young Japanese cedar stands) and a mixed deciduous broadleaved forest (Quercus serrata, Japanese oak stands), we investigated the fate of radiocesium transported by branchflow from upper and lower portions of canopy and deposited by stemflow at trunk basal area. The results showed leachable radiocesium was greater for branchflow that received washoff from the dead foliage than the branchflow receiving radiocesium inputs from mixed and younger foliage. For the tree trunk, radiocesium leached more in stemflow from the lower part as compared to the upper part, possibly due to the increased residence time of stemflow on the lower reaches of the trunk. Further work should examine the effect of bark water capacity and its relationship with the 137Cs vertical distribution and isotopic composition of each tree stands.