Using Cs-137 technique to investigate the spatial distribution of erosion and deposition regimes for a small catchment in the black soil region, Northeast China

摘要

Researches on the spatial distribution of erosion and deposition regimes are important to understand soil erosion mechanism and effectively implement soil and water conservation measures within watersheds. However, traditional monitoring techniques provide limited information for that at the catchment scale. Based on the Cs-137 tracer and GIS technology, this study clarified the spatial distribution of erosion and deposition regimes within a small catchment (Dongshan catchment), which has typical representativeness in the black soil region of Northeast China. The local Cs-137 reference inventory was 2378.4 Bq m(-2), and the summit of convex slope was preferably taken as the reference site when undisturbed sites were inexistence in the study area. Estimates of soil redistribution rates derived from Cs-137 measurement ranged from -35.89 to 53.63 t ha(-1) yr(-1), with about 95.65% of the net soil loss coming from the slope surface. The average soil erosion intensity within the catchment was 4.54 t ha(-1) yr(-1) and it was 1.51 t ha(-1) yr(-1) in the gully area, but both were above the tolerance erosion rate in the black soil region of Northeast China. Further, gully head made the leading contribution to the gully erosion. When the geographical location shifted from the upstream to the middle-stream then to the down-stream of the catchment, the mainly erosion regimes changed from detachment-dominant to coexisting detachment and deposition dominant, and then deposition-dominant regime. Along the slope length, erosion rate increased from the summit to the shoulder and back slopes, and then decreased at the foot-slope, while at the toe of slope deposition occurred. However, erosion pattern along the slope was affected by the slope shape. For the convex slope, the most severe erosion location was the back of slope, while for the concave slope it was the shoulder of slope; erosion rate of the summit and foot slope for the convex slope was 0.5 and 1.97 times that of the concave slope