title: Tracing the source of sedimentary organic carbon in the Loess Plateau of China: An integrated elemental ratio, stable carbon signatures, and radioactive isotopes approach.
abstract: Soil erosion, which will induce the redistribution of soil and associated soil organic carbon (SOC) on the Earth's surface, is of critically importance for biogeochemical cycling of essential elements and terrestrial carbon sequestration. Despite the importance of soil erosion, surprisingly few studies have evaluated the sources of eroded carbon (C). This study used natural abundance levels of the stable isotope signature (13C) and radioactive isotopes (137Cs and210Pbex), along with elements ratio (C/N) based on a two end member mixing model to qualitatively and quantitatively identify the sources of sedimentary OC retained by check dam in the Qiaozigou small watershed in the Loess Plateau, China. Sediment profiles (0-200 cm) captured at natural depositional area of the basin was compared to possible source materials, which included: superficial Loess mineral soils (0-20 cm) from three land use types [i.e., grassland (Medicago sativa), forestland (Robinia pseudoacacia.), shrubland (Prunus sibirica), and gully land (Loess parent material.)]. The results demonstrated that SOC in sediments showed significantly negative correlation with pH (P < 0.01), and positive correlation with soil water content (SWC) (P < 0.05). The sedimentary OC was not derived from grasslands or gullies. Forestland and shrubland were two main sources of eroded organic carbon within the surface sediment (0-60 cm deep), except for that in the 20-40 cm soil layer. Radionuclides analyses also implied that the surface sediments retained by check-dams mainly originated from soils of forestland and shrubland. Results of the two end-member mixing model demonstrated that more than 50% SOC (mean probability estimate (MPE) 50.13% via13C and 60.53% via C/N) in surface sediment (0-20 cm deep) derived from forestland, whereas subsurface sedimentary SOC (20-200 cm) mainly resulted from shrubland (MPE > 50%). Although uncertainties on the sources of SOC in deep soils exist, the soil organic δ13C and C/N is still an effective indicator for sources of sedimentary organic carbon in the deposition zone in the short term (<10 years).
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shanxi, 712100, PR China; College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China.
authors.forename: Chun
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shanxi, 712100, PR China; Tianshui Soil and Water Conservation Experimental Station, Yellow River Conservancy Commission, Tianshui, Gansu Province, 741000, PR China. Electronic address: hwtsdyt@163.com.
authors.forename: Yuting
authors.initials: Y
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shanxi, 712100, PR China; College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China. Electronic address: lizw@hnu.edu.cn.
authors.forename: Zhongwu
authors.initials: Z
authors.lastname: Li
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shanxi, 712100, PR China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Chang
authors.affiliation: College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Nie
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shanxi, 712100, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shanxi, 712100, PR China.
authors.forename: Haibing
authors.initials: H
authors.lastname: Xiao
authors.affiliation: College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China.
authors.forename: Hassan
authors.initials: H
authors.lastname: Bashir
mesh_terms: D002244:Carbon / Q000032:analysis*; D002681:China; D004784:Environmental Monitoring / Q000379:methods*; D065948:Grassland; D006812:Humic Substances; D011868:Radioisotopes / Q000032:analysis
chemical_list: D006812:Humic Substances; D011868:Radioisotopes; D002244:Carbon
keywords: Check-dam; Isotopes; Land use types; Loess Plateau; Sediment; Soil organic carbon