Keywords:Radiocesium leaching, Stemflow, Branchflow, Coniferous and deciduous trees , Fukushima Dai-ichi Nuclear Power Plant accident
Fukushima Dai-ichi Nuclear Power Plant accident has released a massive amount of radiocesium into the forest ecosystem in the past 7 years ago. Thus, the initial fallout majorly intercepted and attached to the canopy, especially for evergreen forest such as cedar stands. However, for deciduous broad-leaved forest such as for oak stands, the major exposed were branches and stems since at the time of the accident the leaves had already fallen. Through precipitation events, radiocesium from the canopy has washed out to the branch and then channeled to the trunk via preferential pathways before deposited onto the forest floor time to time. Hence, this radiocesium leaching through stemflow and branchflow demonstrates an important component in the deposition and cycle process of radiocesium. As the deposition flux of radiocesium was enriched by stemflow generation per rainfall event, far less is known on which part of the forest stand, either at the canopy and/or trunk that contributing to this leaching process. Therefore, in this study, we investigated the relationship between radiocesium leaching and stemflow generation of the coniferous forest (young Japanese cedar trees) and mixed deciduous broad-leaved forest (Japanese oak trees). In more details, we also determined the different pathway of radiocesium leaching for branchflow through young and old foliage and for stemflow at the various height of canopy and trunk based on different collector setup.