Serpentinitic soils contain high concentration of geogenic Ni.During serpentinitic mineral weathering,the release of Ni from the soils into ecosystems suggests a possible source of non-anthropogenic metal contamination.This study collected the soil samples of two pedons in the paddy fields from Taiwan and Japan to explore the profile distribution of total and labile Ni for demonstrating the contribution of Ni-bearing Fe and Mn oxides on Ni partition in these soils.Serpentine and chlorite were the dominant primary minerals,reflecting the characteristics of serpentinites and high background concentration of Ni in the soils.In all soil horizons,total Ni content ranged from 240 to 520 mg kg-1.However,the repeated redox and leaching cycles led to re-distribution of Ni in these paddy soils.The DTPA(diethylenetriamine pentaacetate)-extractable Ni,an availability index of Ni,decreased with soil depth in the two pedons.An additional pool of labile Ni was present in the soils,because the Ni concentration with the 0.1 N HCl extraction was much higher than that with the DTPA extraction.Fe and Mn oxides were closely related to the labile Ni in these paddy soils.However,Ni was predominantly retained with amorphous and crystalline Fe oxides in comparison to Mn oxides.Appropriate management strategies are required to reduce the solubility of Ni the paddy soils,because that the labile Ni and redox-sensitive Fe oxides can affect paddy soils and the environment when Ni is released into the soil solution and become bioavailable.