A study of soil surface characteristics in a small watershed in the hilly, gullied area on the Chinese Loess Plateau

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Abstract
Soil surface characteristics are closely related to soil surface depressional storage, infiltration, runoff generation and soil erosion, especially in highly erodible loess soil. Soil surface random roughness, soil cohesion and aggregate stability are necessary parameters in the Limburg Soil Erosion Model (LISEM) and helpful in developing alternative land-use and conservation strategies. Over a period of 2 years, soil surface characteristics were measured continuously in Danangou, a small catchment in the hilly, gullied loess area in China, with the support of the Erochina project. The results show that soil surface random roughness, soil cohesion and aggregate stability differed significantly between land-use types. Ranking the types on soil roughness during the monitoring period yielded the sequence cropland>orchard and wasteland and fallow land>shrubland>woodland. The corresponding sequence for aggregate stability was approximately wasteland and woodland>cropland and orchard>shrubland>fallow land. Cohesion in the different land-use types in the catchment was smallest for cropland and largest for wasteland. There were no significant differences between croplands with different topographical characteristics. All of these soil surface characteristics showed significant temporal variation over the monitoring period. Temporal variations in roughness for shrubland and woodland over the 2-year period were significantly greater than those for other land-use types. There were also considerable variations in cohesion for shrubland, woodland and wasteland. In 1998, the weighted average values of roughness, aggregate stability and cohesion for the entire catchment were 1.113 cm, 13.6 drops and 0.131 kg/cm2, respectively, with C.V. values of 9.6%, 32.05% and 21.11%. The corresponding values for 1999 were 1.616 cm, 11.52 drops and 0.100 kg/cm2, with C.V. values of 16.0%, 15.41% and 33.33%. The temporal and spatial variations in soil surface characteristics in the catchment should be carefully taken into account in LISEM calibration and validation.