Soil Erosion-induced Selective Transfer of Organic Carbon in Red Soil Slope Field under Natural Rainfall
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Supported by the National Natural Science Foundation of China (No. 41303064), the Special Fund for Water Resources Research in the Public Interest (No.2014BAD15B0303) and the Major Research Projects of Water Resources Department of Jiangxi Province (No. KT201417)

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    Abstract:

    【Objective】The red soil hilly region in South China is one of the areas of the country suffering serious soil erosion. Currently, the researches on loss of soil organic carbon with soil erosion in this region were executed mainly via simulated rainfall tests, without much in-situ field quantitative monitoring under natural rainfalls or comparison between fields different in land use. This study was intended to explore relationships of surface runoff and sediment loss with organic carbon carried in runoff and sediment under natural rainfall, so as to characterize responses of soil organic carbon transfer and loss to changes in rainfall, soil erosion and land use, and to deepen the scientific knowledge about relationship between soil erosion and carbon recycling.【Method】Tracts of bare land, grassland,, citrus orchard, and secondary splash pine forest were selected for the experiment as runoff plots in the Jiangxi Soil and Water Conservation Ecological Science Park. Surface runoff, sediment loss and soil organic carbon carried therein were monitored under 24 typical rainfalls between March to August, 2015 in order to illustrate selective transfer of soil organic carbon. 【Result】Results show as follow: (1) Runoff coefficients and the soil erosion modulus increased with increasing rainfall intensity during all the 24 rainfall events. With the conversion of land use in type from bare land to orchard, grassland and forest, the effects of land use reducing runoff and sediment increased. Rainfall intensity was the major factor affecting runoff volume, while the latter was the one affecting sediment loss, with correlation coefficient being 0.89~0.92 (p <0.001) and 0.95~0.98 (p <0.05), respectively. (2) Under natural rainfalls, the concentration of organic carbon was 5.00, 7.68, 6.11 and 10.02 mg L-1 in runoff and 7.69, 8.58, 8.08 and 8.93 g kg-1 in sediment on the bare land, grassland, orchard and forest, respectively. The concentration of organic carbon in runoff was significantly and negatively related to volume of the runoff and so was the concentration in sediment with the volume of sediment loss. The sediment-associated loss of soil organic carbon in the four plots accounted for 64.67%, 47.38%, 53.94% and 36.03% of the total lost with the erosion, and reached 560.3 mg m-2, 1.98 mg m-2, 122.5 mg m-2 and 2.66 mg m-2 in intensity, respectively. (3) The organic carbon enrichment ratio of the sediment in the bare land, orchard, grassland and forest was 1.27, 1.10, 0.80 and 0.58, respectively, and decreased gradually with increasing rainfall intensity. Selective transfer of organic carbon was more evident in weak rainfalls.【Conclusion】Under natural rainfalls, soil erosion has very important impacts on migration of soil organic carbon in slope fields in the red soil region. Selective migration of soil organic carbon with surface runoff or sediment is determined mainly by rainfall characteristics (especially rainfall intensity) and land use pattern. In all the lands, regardless of land use, intensified soil erosion makes it easier for soil organic carbon to migrate with sediment, and organic carbon enrichment ratio of the sediments also increases with intensifying soil erosion. However, organic carbon enrichment ratio of the sediment decreases with rising rainfall intensity.

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XIAO Shengsheng, TANG Chongjun, WANG Lingyun, DUAN Jian, YANG Jie. Soil Erosion-induced Selective Transfer of Organic Carbon in Red Soil Slope Field under Natural Rainfall[J]. Acta Pedologica Sinica,2017,54(4):874-884.

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History
  • Received:August 28,2016
  • Revised:December 02,2016
  • Adopted:December 22,2016
  • Online: April 28,2017
  • Published: