Quantifying soil erosion effects on soil productivity in the dry-hot valley, southwestern China

The dry-hot valley region (DHV) in southwestern China is one of the most ecologically fragile zones in China with intensive soil erosion. Few studies have focused on the effects of soil erosion on soil productivity in this region. The objectives of this study were to quantify the effects of soil erosion on soil productivity using the 'soil erosion class' method. The degree of soil erosion was investigated at 44 monitoring sites in typical DHV catchments, and soil physicochemical properties, and corn yield at each site were monitored. The results showed that soil productivity was significantly affected by soil erosion in the DHV. As the degree of soil erosion progressed from 'slight' to 'moderate' to 'severe,' organic matter content decreased 15.29, 18.00, and 27.37 %, alkali-hydrolyzable nitrogen-0.06, 6.03, and 9.45 %, and available potassium content-7.07, 41.79, and 43.32 %, respectively. Compared with the 'no' erosion site, the decreases in the mean corn seed yields were 1.56 % for 'slight,' 29.18 % for 'moderate,' and 35.03 % for 'severe' erosion. These results indicated that once the erosion reached 'moderate' levels, significant reductions in soil productivity were present. The declining slope of corn seed yields was 0.13 Mg ha(-1) cm(-1) of topsoil loss. The estimated mean for the absolute corn loss was 0.01 Mg ha(-1) year(-1) in the DHV. These results increased the understanding of the mechanism of soil degradation processes in the DHV and will be instrumental in developing a strategy for ecological restoration.