Soil Physical Degradation Affected by Gully Erosion in Cultivated Slope Land on the Loess Plateau

摘要

Gully erosion was an universal process in cultivated slope land on the Loess Plateau. which exerted serious effects on soil quality. In this study, 64 sampling sites with erosion gully were selected and soil samples in the profile were taken at erosion gully and inter-gully area nearby. The distribution characteristics of soil bulk density, soil particle composition. soil aggregate and organic matter content in different depth of gully erosion were analyzed. Soil properties in inter-gully were chosen as the control. The objectives of this work were: 1) to clarify the response of soil physical properties to gully erosion; 2) to quantify soil physical quality degradation under different gully erosion degree and 3) to identify sensitive soil physical indicators for erosion soil quality. The results showed that. there was no significant degradation in soil physical properties that we measured in the initial of gully erosion with less than Scm depth. Soil bulk density and content of aggregate over Smm increased by 11.8 and 10.8 percent, respectively, when gully's depth increased from 5 to 40cm. While soil specific area (SSA/(cm2·g-1)), mean weight diameter (MWD/mm) and soil clay content decreased by 4.0%. 14.3% and 14.4%, respectively. Soil texture showed a desertification trend and fertility was declined significantly (p<0.05). No significant degradation in soil physical quality was found at the depth of 40-50cm in gullies. Fine particle losing was the main cause for degradation of soil physical quality. Soil structure was degraded significantly at the depth of 5-25cm in gullies. Erosion depth of Scm and 25cm were the two critical points where the soil physical property and organic matter reduced rapidly in the soil profile of erosion gully. Soil physical degradation under gully erosion could be characterized by soil granular structure destructing, texture coarsening and surface soil hardening. The decline of soil organic matter content was coupled with soil physical degradation.