Abstract: In the black soil region of Northeast China,soil and water loss is quite serious, but not fully investigated due to the lack of reliable methods.¹³⁷Cs technology is a good one to study the medium-and long term erosion and sedimentation rates and the spatial redistribution of soil.With this technology and the existing calibration models,this paper studied the redistribution patterns of black soil in a typical hillslope landform of Northeast China.The results showed that in the study area,the reference ¹³⁷Cs value was 2232.75 Bq·m^-2,intervenient the background values in the Yangtse River Delta and Loess Plateau;and the¹³⁷Cs areal activity had a great differentiation in horizontal and vertical directions,being the lowest in the shoulder-slope positions,which suggested that the summits and back-slope positions suffered weak erosion,and some of the eroded soils were redeposited in foot-slope and toe-slope positions.The vertical distribution of ¹³⁷Cs in soil profile ranged from 20 cm on a shoulder-slope to 80 cm on a toe-slope position,indicating a significant erosion and deposition.Estimations with four existing calibration models showed that PM model underestimated while MBM-1 model overestimated the soil erosion rates very obviously,and both MBM-2 and MBM-3 gave similar and reasonable estimations.

Key words: Unsymmetrical cutting, Symmetrical cutting, Mixed model, Rainstorm-runoff process