Can soil conservation practices reshape the relationship between sediment yield and slope gradient?
2020
Wu, Lei | He, Yin | Ma, Xiaoyi
Sloping farmland is widely distributed in Chinese loess hilly regions but the coupling mechanism between slope gradient and sediment yield was not clear in a large-scale ecological restoration watershed. A piecewise sediment delivery ratio (SDR) algorithm was embedded in the Revised Universal Soil Loss Equation (RUSLE) to identify the spatiotemporal responses of sediment yield to slope gradient before and after “Grain for Green” project in the Yanhe River Watershed. Results indicate that: (i) The sediment yield rate in the Yanhe River Watershed varied greatly from 1995 to 2012 but it presented an overall decreasing trend especially after 2006, the average sediment yield rate was 1013.3 t·km−2 from 2009 to 2012, which decreased by 80.7% compared with the early stage of “Grain for Green” project (1995–1998). The high risk regions of sediment yield were mainly concentrated in the sloping farmlands located at the main stream banks of Yanhe River. (ii) The contribution ratio of steeper slope under each sediment yield rate increased gradually with increased sediment yield rate in 1995, while only the contribution ratio of 15°~20° slope presented a significant increasing trend in 2010. (iii) The slope classification of the highest contribution ratio transferred from 0°~15° to 15°~20° when the sediment yield rate was >30 t·ha−1 in 1995, but 15°~20° always dominated the key contribution of sediment yield under each sediment yield rate in 2010. Results could provide new understanding for reasonable soil conservation planning and management of sloping farmland in loess hilly regions.
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