Effects of the slope aspect and leaf mass on the radiocesium spatial distribution of fallen leaves of Quercus serrata

Abstract

In this study, we evaluated the spatial distribution of radiocesium in a forest and explored its causal factors. We set 61 litter traps and collected the fallen leaves of a dominant tree species, Quercus serrata, in a deciduous broad-leaved forest in 2011 and 2012. Then we examined relationships between the radiocesium of fallen leaves and the aspect, gradient of slope, leaf mass. The spatial distribution of radiocesium in the fallen leaves was not uniform in 2011: radiocesium concentrations in fallen leaves were higher at the east-facing slope compared to those at the west-facing one, and were higher at sites with higher leaf mass. Although the spatial bias was smaller in 2011, the same tendency was observed. Eastward wind direction at the study site when massive radiocesium was emitted from the Fukushima Daiichi Nuclear Power Plant was considered as one of the reasons for the phenomenon.