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Title: Effects of near soil surface characteristics on soil detachment by overland flow in a natural succession grassland

Author
item WANG, BING - Northwest Agricultural & Forestry University
item ZHANG, GUANGHUI - Beijing Normal University
item Zhang, Xunchang
item LI, ZHENWEI - Northwest Agricultural & Forestry University
item SU, ZILONG - Beijing Normal University
item SHI, YANGYANG - Shanxi University
item YI, TING - Beijing Normal University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2013
Publication Date: 3/21/2014
Citation: Wang, B., Zhang, G., Zhang, X.J., Li, Z., Su, Z., Shi, Y., Yi, T. 2014. Effects of near soil surface characteristics on soil detachment by overland flow in a natural succession grassland. Soil Science Society of America Journal. 78:589-597.

Interpretive Summary: Conversion of cropland to natural grasslands can have great effects on soil detachment and soil loss. This study was conducted to investigate the effects of near soil surface characteristics on soil detachment by overland flow in a 7-year naturally restored grassland. Four treatments were designed to characterize the effects of dead roots, live roots, biological soil crusts (BSCs), and plant litter-stems in succession. For comparison, an undisturbed bare Loess soil was used as a check. The soil surface was prepared or disturbed to isolate the effects of the four treatments. Each treatment was subjected to flow scouring under five different flow rates to simulate concentrated water flow. The results showed that near soil surface properties of plant litter-stem, BSCs, and plant roots enhanced the resistance of soil to water detachment significantly. With these factors subsequently superimposed, soil detachment capacity decreased progressively. Taken together, the 7-year restored natural grassland would decrease soil detachment capacity by 98.9% compared with the bare Loess soil, in which plant litter-stem, BSCs, and total roots contributed to 30.3%, 14.9%, and 53.7%, respectively. Furthermore, for the total root effects, chemical bonding of root exudates accounted for 14.7% while physical binding of root systems accounted for 39.0%. These results can be used by modelers to adjust soil erosion models' soil detachability or erodibility to account for the effect of roots, surface crusts, and surface litter-stems on soil erosion. Soil and water conservationists can also use this information to assess the effectiveness of various soil surface conditions in controlling soil erosion.

Technical Abstract: Vegetation restoration probably has great effects on the process of soil detachment. This study was conducted to investigate the effects of near soil surface characteristics on soil detachment by overland flow in a 7-year naturally restored grassland. Four treatments were designed to characterize the effects of dead roots, live roots, biological soil crusts (BSCs), and plant litter-stems in succession. For comparison, an undisturbed bare Loess soil was used as a baseline. The testing area (1.0 m in length and 0.1 m in width) of each treatment was subjected to flow scouring under five different shear stresses ranging from 6 to 13 Pa. The results showed that near soil surface properties of plant litter-stem, BSCs, and plant roots enhanced the resistance of soil to water detachment significantly. With these factors subsequently superimposed, soil detachment capacity decreased progressively. Taken together, the 7-year restored natural grassland would decrease soil detachment capacity by 98.9 % compared with the bare Loess soil, in which plant litter-stem, BSCs, and total roots contributed to 30.3 %, 14.9 %, and 53.7 %, respectively. Furthermore, for the total root effects, chemical bonding of root exudates accounted for 14.7 % while physical binding of root systems accounted for 39.0 %. Results also indicated that BSCs were unable to protect the soil from detachment when the shear stress was greater than 11 Pa, and tended to accelerate soil erosion. This paper developed an equation for adjusting WEPP’s rill erodibility for use in natural succession grassland in the Loess Plateau of China, and the result seemed satisfactory with the Nash-Sutcliffe efficiency (NSE) coefficients ranging from 0.28 to 0.77. Further studies are needed to detect the dynamics of near soil surface characteristics with succession age of grassland in the Loess Plateau.