Efficacy of soil moisture conditions on the formation of ectomycorrhizal colonization and ¹³⁷Cs absorption

Oak represents one of the most adaptable and resilient trees on earth and is widely distributed in multiple environments ranging from wet to dry. Japanese oak forests of Fukushima and the northern Kanto area were contaminated with radiocesium (¹³⁷Cs) by Fukusima Dai-ichi nuclear Power Plant accident. ¹³⁷Cs trapped at the surface soil has a deleterious effect on forest ecosystem and poses further threat to humans when it enters the food chain. The uptake of ¹³⁷Cs and other essential nutrients such as nitrogen (N), phosphorus (P) and potassium (K) by plants with the aid of ectomycorrhizal fungi is affected by soil water content. The objective of this study was to evaluate the colonization rate of ectomycorrhiza (CRE) and its impact on nutrients and ¹³⁷Cs uptake pattern by oak (Quercus serrata Thunb.) seedlings at different soil water content levels under greenhouse condition. The result shows that the growth of Q. serrata seedlings increased with increasing soil water content. In addition, the highest CRE was observed in the low water content (LW) and was significantly different from the high water content treatment (HW). The LW treatment showed the highest N and P concentration in leaves and roots although no statistical differences were observed compared to the other treatments. Treatments with ¹³⁷Cs-amended litter showed increased ¹³⁷Cs concentration in the leaves of plants and its leaf per root ratio increased with decreasing soil water content. The results of the present study also suggest enhanced ¹³⁷Cs absorption and translocation into Q. serrata seedlings is with the aid of ectomycorrhizal fungus except for the seedlings in HW.