ABSTRACT
Human-induced accelerated erosion, after the removal of natural vegetation, has been attributed as the major cause of soil degradation of the Loess Plateau of China. In this paper, relationships between soil erosion and soil degradation processes from a secondary forest region of the Loess Plateau were quantified. Natural runoff plots were installed at different hillslope positions, representing different forms of dominant erosion processes from sheet, rill to shallow gully, in a newly deforested area. Sediment samples were collected after each rainfall event and analyzed for organic matter and nutrient content. Results showed that the loss of soil nutrients increased with increasing intensity of erosion. Linear relationships were found between total N, organic matter, NH4-N, and available P and intensity of erosion. Nutrient content per unit of eroded sediment decreases while total nutrient loss increases from sheet erosion to shallow gully erosion. Comparing nutrients in the eroded sediment against those in the top 0.2 meter of the soil, we found consistently higher concentrations or enrichment for NH4-N and available P. Degrees of soil degradation are closely related to different erosion intensities and patterns, i.e., interrili, rill and shallow gully, spatially along a hill slope.
