Transfer of Cs-137 from soil to plants in a wet montane forest in subtropical Taiwan

The distribution of Cs-137 in an undisturbed, multistoried, subtropical wet montane forest ecosystem surrounding Yuanyang Lake (lake surface level ca. 1670 m, in northeastern Taiwan), was investigated. The mossy forest here r epresents a currently-rare perhumid temperate environment in subtropical re gion. The radioactivity concentration of Cs-137 was determined by gamma-spe ctroscopy with a Ge(Li) detector. Although the soil is extremely acidic (pH 3.3 to 3.6) and the rainfall is high, Cs-137 is evidently retained in the organic layer. The radioactivity concentration of Cs-137 is surface soil ra nges from 28 to 71 Bq . kg(-1). The concentrations of Cs-137 in the ground moss layer and litter were much lower than that in the soil organic layer, this suggests that Cs-137 detected is not from the newly deposited radioact ive fallout. The radioactivity concentration and transfer factor (rn of Cs- 137 varied with plant species. Shrubs and ferns have higher values than a c oniferous tree (Taiwan cedar). The TF in this ecosystem is as high as 0.21 to 1.88. The high values of TF is attributed to the abundance of the organi c matter in the forest soils. The rapid recycling of Cs-137 through the soi l-plant system of this undisturbed multistoried ecosystem suggests the exis tence of an internal cycling that help thr accumulation of Cs-137 in this e cosystem.