2021 Volume 20 Issue 2 Pages 83-100
Bracken (Pteridium aquilinum subsp. japonicum) is a fern with edible young leaves. To clarify the growth of bracken and temporal changes in the levels of radiocesium released from the 2011 TEPCO Fukushima Daiichi Nuclear Power Station accident in bracken, we have investigated bracken communities in former pasture since 2017. We also tested the effect of potassium (K) application on reducing radiocesium concentrations. From spring to autumn, when the leaves are green, about 40% of bracken’s biomass is comprised of leaves while the other 60% consists of belowground organs (rhizomes and roots). There is little seasonal difference in the total plant biomass. The cesium-137 (137Cs) concentrations in bracken varied among organs such as young leaves, adult leaves, and belowground organs, reflecting seasonality, but the total concentrations in plants decreased gradually (P = 0.023). The decline, as approximated by an exponential function, was 27% per year. After application of K in June 2017, total potassium-40 concentrations of treated bracken plants were higher than those of control plants from about August to March of the following year. Consequently, the 137Cs concentrations of the treated bracken were suppressed to about 70% of those of the control plants (P < 0.001).
