SOIL EROSION RATE ESTIMATION USING 137CS TECHNIQUE IN RED SOIL REGION, SOUTHERN CHINA.

The 137Cs tracer technique has been used extensively to estimate soil erosion rates around the world, but few reports have discussed the soil erosion rate in the red soils of southern China. The high amount of intensive rainfall and the low soil water infiltration rate of the region make the identification and determination of 137Cs reference inventory difficult. The objectives of this study were to examine the 137Cs redistribution in the red soil region and to use a new proposed relative 137Cs inventory method to build a reference series to estimate the rate of soil erosion. A set of 6-point samples along a toposequence section was selected for investigation of 137Cs distribution in the red soil region. 137Cs distribution in the depth function was not correlated with the contents of organic matter and clay, indicating the redistribution of 137Cs was controlled not only by soil erosion but also by high runoff and a low soil water infiltration rate. Thus, the relative 137Cs reference inventory method was introduced to estimate the soil erosion rate in the study region. Moreover, a mass-balance estimation model was employed to calculate the rate of soil erosion based on the conventional, effective, and relative references. Overestimation of the conventional and effective methods at the summit point was significant. Hence, use of the relative 137Cs reference inventory method would explain the specific soil erosion rate in the study area better than the conventional and effective reference inventory methods. However, more validation studies are required in its general application to other regions.