The severity of soil erosion is considered to vary according to the structure of the bench terrace and the ground cover conditions. Erosion losses were investigated in a field experiment based on 20 m × 5 m erosion plots on a 21 per cent slope in Southern China. Five plots were established for the present study. Rainfall, runoff and sediment yield from plots were recorded for 5 years (2001–2005) and which five different types of terraces on sloping red soil were compared. The results show that the planting of grass on the riser is the most important factor affecting runoff and sediment yield, the next most important factor was the construction of a bund built on the edge of the terrace. Although the terrace bed slope (slope < 5 degrees) does not significantly affect the runoff, it does benefit the soil. A terrace combined with vegetation measures is effective in controlling runoff and soil erosion. Among various terraces, the level terrace (i.e. grass planted on the riser and bunds built on the edge of a bench terrace) is apparently the most beneficial for soil conservation purposes, indicating that this type is an excellent choice for conserving soil and water resources in sloping red soil in Southeastern China. Copyright © 2012 John Wiley & Sons, Ltd.

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Abstract:A study was undertaken to develop an appropriate plan of land use under suitable slope gradient to control soil erosion from a red soil hilly watershed of southern China by using the GeoWEPP (Geo-spatial Interface for the Water Erosion Prediction Project) model. The model was calibrated and validated using monitoring data of the outlet from 2010 to 2012, in which the 2010 and 2012 annual total runoff and sediment yield data were used for calibration, and the 2011 monthly runoff and sediment yield data for validation. The performance of the model in validation period were good with a high coefficient of determination values of 0.98 and 0.93 and Nash-Sutcliffe simulations of 0.96 and 0.91 while low root mean square error values of 6.91 mm and 0.35 t respectively for runoff and sediment yield. Subsequently, the model was used to simulate four typical land use (forest, farm, orchard, and fallow land) in the study area to evaluate their impacts on soil erosion production. The results showed that the runoff decreased by 44.7% and 61.1% for forest and orchard land compared to the current land use, as well as the sediment yield OPEN ACCESSSustainability 2015, 7 14310 decreased by 43.7% and 68.6%. While the runoff and sediment yield increased by 52.2% and 42.6% for farm land, and 48.8% and 29.6% for fallow land. As the same time, soil erosion increased with increasing of the slope gradient of the quadratic regression equation for all land use. The critical slope gradient of 15° for returning the farmland to forest or others is suitable in the red soil region but is not accurate. The result of the study provides good scientific evidence for developing an appropriate plan of land use in the watershed and other similar areas.

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Phytogenic mounds (nebkhas) formed by shrubs are a common phenomenon in arid and semiarid areas and play important roles in preventing soil erosion and nutrient loss. One feature of nebkhas is the development of fertile islands. We investigated whether fertile islands were present inside and underneath Caragana tibetica-formed nebkhas in the northwest portion of the Ordos on the Inner Mongolia Plateau, China, and if such a fertile island effect increased with the age of the nebkhas. We also analyzed the spatial heterogeneity of the soil properties and quantified the amount of sand trapped by C. tibetica. The morphometric characteristics of C. tibetica nebkhas were investigated in a 4.5 ha area. Soil samples were collected inside, underneath and outside of the nebkhas and the soil organic matter (SOM), total phosphorus (TP), soil moisture (SM) and soil texture were determined. The SOM, TP and SM inside and underneath nebkhas at later stages of growth were higher than those at smaller, younger growth stages, which in turn were higher than those outside the nebkhhas. Inside the nebkhas at the establishment and early growth stages, SOM and TP first increased and then decreased with increasing soil depth, but SM steadily increased. The amount of sand trapped by C. tibetica per unit area was 0.0313 m 3 m −2 . Nebkhas of C. tibetica primarily accumulated fine sand, which accounted for 74% of the soil, and is significantly higher than that outside the nebkhas. Caragana tibetica significantly increased sand entrapment, and fertile islands are formed inside and underneath C. tibetica nebkhas.

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