Estimation of suspended sediment sources using 137Cs and 210Pbex in unmanaged Japanese cypress plantation watersheds in southern Japan.

The article presents an estimation of suspended sediment sources with the use of ¹³⁷Cs and ²¹⁰Pb_ex in unmanaged cypress plantation watersheds in southern Japan. The ¹³⁷Cs and ²¹⁰Pb_ex were detected with the use of gamma-ray spectrometry in the surface soil of forest floor, stream bank and others. The multivariate sediment-mixing model that use ¹³⁷Cs and ²¹⁰Pb_ex showed that the contribution of the forest floor changes in various subwatersheds. Results show that the forest floor should be recognized as a source of suspended sediment in unmanaged cypress plantation watersheds.