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Title: Soil detachment by overland flow under different vegetation restoration models in the loess plateau of China

Author
item WANG, BING - Beijing Normal University
item ZHANG, GUANG-HUI - Beijing Normal University
item SHI, YANG-YANG - Beijing Normal University
item Zhang, Xunchang

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2013
Publication Date: 1/21/2014
Citation: Wang, B., Zhang, G., Shi, Y., Zhang, X.J. 2014. Soil detachment by overland flow under different vegetation restoration models in the loess plateau of China. Catena. 116:51-59.

Interpretive Summary: Soil erosion is a worldwide problem causing land degradation. Vegetation cover is effective in reducing soil erosion. This work is to quantify the effects of naturally restored vegetation on soil detachment and entrainment by concentrated flow in a silt loam loessial soil, and to evaluate soil's resistance to flow detachment for five vegetation restoration models. The undisturbed soil cores (98 mm id and 50 mm tall) were collected from five 37-year-restored lands of abandoned farmland, korshinsk peashrub land, black locust land, Chinese pine land and mixed forest land of amorpha and Chinese pine. The samples were subjected to flow scouring in a 4.0 m long by 0.35 m wide hydraulic flume under six different shear stresses or flow powers. The results showed that the measured soil detachment capacities were affected significantly by the restoration models. The mean detachment capacities of cultivated farmland were 23.2 to 55.3 times greater than those of the restored or converted lands. Abandoned farmland showed maximum value of soil detachment capacity and was 1.02 to 2.29 times greater than the other four restored woodlands. Soil detachment capacity of the restored lands was significantly influenced by flow power, soil cohesion, bulk density, and root mass density. Overall results showed that vegetation restoration reduced soil detachment (erosion) significantly, compared with those of cultivated lands, demonstrating that conversion of croplands to grasslands or woodlands is an effective way to control soil erosion and conserve the soil resource. These results provide useful information to farmers and soil conservationists on converting croplands to grasslands or woodlands for soil conservation.

Technical Abstract: Land use change has significant effects on soil properties and vegetation cover and thus probably affects soil detachment by overland flow. Few studies were conducted to evaluate the effect of restoration models on the soil detachment process in the Loess Plateau in the past decade during which a Great Green Project was implemented. This study was performed to study the effects of vegetation restoration models on soil detachment by overland flow and soil resistance to erosion as reflected by soil erodibility and critical shear stress. The undisturbed soil samples were collected from five 37-year-restored lands of abandoned farmland, korshinsk peashrub land (Caragana korshinskill Kom.), black locust land (Robinia pseudoacacia Linn.), Chinese pine land (Pinus tabuliformis Carr.) and mixed forest land of amorpha and Chinese pine. The samples were subjected to flow scouring in a 4.0 m long by 0.35 m wide hydraulic flume under six different shear stresses ranging from 5.60 to 18.15 Pa. The results showed that the measured soil detachment capacities were affected significantly by the restoration models. The mean detachment capacities of cultivated farmland were 23.2 to 55.3 times greater than those of the restored or converted lands. Abandoned farmland showed maximum value of soil detachment capacity and was 1.02 to 2.29 times greater than the other four restored lands. Soil detachment capacity of the restored lands was significantly influenced by shear stress, cohesion, bulk density, total porosity and root mass density. Detachment capacities was negatively related to cohesion (p<0.01) with power function and root mass density (p<0.05) with exponential function, but positively to total porosity (p<0.01) with power function. The rill erodibility would be negatively related to cohesion (p<0.01) with power function. Besides, the low rill erodibility in the restored lands always had a low soil detachment capacity, while the critical shear stress in the restored lands varied non-monotonically with detachment capacity. The mixed forest land of amorpha and Chinese pine was considered as the best restoration model for its important role in reducing soil detachment capacity.