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Title: Flow detachment of soils under different land uses in the Loess Plateau of China

Author
item ZHANG, G - BEIJING NORMAL UNIVERSITY
item LIU, G - ISWC, CHINA
item TANG, K - BEIJING NORMAL UNIVERSITY
item Zhang, Xunchang

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2008
Publication Date: 6/1/2008
Citation: Zhang, G.H., Liu, G.B., Tang, K.M., Zhang, X.J. 2008. Flow detachment of soils under different land uses in the Loess Plateau of China. Transactions of the ASABE. 51(3):883-890.

Interpretive Summary: Land use types often have predominant effects on surface water runoff generation and soil loss in fields or watersheds. This study was conducted to evaluate the effects of land use on soil detachment (soil mobilization by flow) of natural, undisturbed soil samples, which were taken from fields of five typical land uses (cropland, grassland, shrubland, wasteland, and woodland) in the Loess Plateau of China. The intact soil samples were tested under concentrated flow in flumes in laboratory. Flow discharges ranged from 0.25 to 2.0 L s-1 and slope gradients varied from 8.8% to 46.6%. The results indicated that soil detachment rates were significantly influenced by land uses. Cropland soil was most easily detached, followed by grassland, shrub land, wasteland, and woodland soils. The average ratios of soil detachment rates of cropland soil to grassland, shrub land, wasteland, and woodland soils were 2.05, 2.76, 3.23, and 13.32, respectively. The results indicated that conversion of croplands to grasslands and woodlands in the Loess Plateau would considerably reduce soil loss rates in the region. The results are useful to soil conservationists to evaluate the effectiveness of different land use types in controlling soil erosion in the region.

Technical Abstract: Land use has a significant effect on soil properties, and therefore on soil erodibility. In many cases, land use controls soil erosion to a greater extent than does climate change or other system properties, yet only a few studies have quantified the effect of land use on soil detachment rates. This study was conducted to evaluate the effect of land use on soil detachment of natural, undisturbed soil samples, which were taken from fields of five typical land uses in the Loess Plateau of China. Flow discharges ranged from 0.25 to 2.0 L/s and slope gradients varied from 8.8% to 46.6%. The results indicated that soil detachment rates were significantly influenced by land uses. Cropland soil was most easily detached, followed by grassland, shrub land, wasteland, and woodland soils. The average ratios of detachment rates of cropland soil to grassland, shrub land, wasteland, and woodland soils were 2.05, 2.76, 3.23, and 13.32, respectively. Detachment rates were shown to be a power function of flow discharge and slope gradient (determination coefficient =0.93). Both critical shear stress and erodibility were affected by land use. The different land uses in this study resulted in erodibility ranging from 0.0021 to 0.164 and critical shear stress ranging from 2.08 to 6.30. No superiority was found if shear stress is replaced by stream power for detachment prediction and either shear stress or stream power can be used to simulate detachment process in rills. The result indicated that soil detachment rates in rill erosion could be well simulated by hydraulic parameters of stream power, slope, and runoff density, and by soil properties of clay content, bulk density, aggregate median diameter, and soil strength. Further studies are needed to quantify the potential effects of plant root system on detachment rates and to investigate the potential temporal variability of soil detachment rates.