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Paper Number: 118

Stable Carbon Isotopic Composition of Black Carbon in Surface Soil as a Proxy for Reconstructing Vegetation in the Northern China

Lian Liu^{1, 2}

¹Geological Society of China, Beijing 100037, China, liulianen@163.com

²Chinese Academy of Geological Sciences, Beijing 100037, China

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Black carbon (BC) is produced by the incomplete combustion of vegetation and fossil fuels, and is good proxy recording wildfires and palaeovegetation information. Whether it’s stable carbon isotopic composition (δ¹³C_BC) can be used directly for palaeovegetation reconstruction in different climate and vegetation zones is still in debate. We systematically investigated surface soil from the Chinese Loess Plateau (CLP) and the Qinling Mountains (QL), and surface sand from the deserts and dune fields (DD) (including the Mu Us dune field, the Tengger Desert, and the Badain Jaran Desert) in the Northern China. We analyzed the stable carbon isotopic composition of BC (δ¹³C_BC) and organic carbon (δ¹³C_SOC). For surface soil in CLP [1], the δ¹³C_BC values ranged from −27.9‰ to −21.9‰, and the δ¹³C_SOC values ranged from −26.8‰ to −20.9‰. For surface soil in QL [2], the δ¹³C_BC values ranged from −26.7‰ to −21.7‰, and the δ¹³C_SOC values ranged from −26.5‰ to −21.0‰. For surface sand in DD [3], theδ¹³C_BC and δ¹³C_SOC values ranged from −28.2‰ to −23.0‰, −27.4‰ to −22.5‰, respectively. Positive correlations were observed between δ¹³C_BC and δ¹³C_SOC in these three areas, suggesting that local vegetation mainly controls δ¹³C_BC. The difference between δ¹³C_BC and δ¹³C_SOC in these three areas were all in small ranges (−1.5‰ to +1.3‰ in CLP, −2.1‰ to +1.5‰ in QL, −0.2‰ to +3.5‰ in DD), and the difference should be due to isotope fractionation occurring during burning and/or SOC decomposition. The characteristics of vegetation on the CLP, QL, and DD, indicated by δ¹³С_BC and δ¹³C_SOC values, were consistent with those of the modern plants. All these suggest that δ¹³С_BC values for surface soil are controlled mainly by surface plants, and therefore δ¹³С_BC can indicate the palaeovegetation effectively in the Northern China.

Figure 1: Schematic map showing the position of research areas.

The red rectangle in figure shows the locality of the Chinese Loess Plateau, the Qinling Mountains, and the deserts and dune fields in the Northern China.

References:

[1] Liu L (2013) Palaeogeogr. Palaeoclimatol. Palaeoecol. 388: 109-114

[2] Liu L and Huang M (2016) ACTA GEOL SIN-ENGL 90 (accepted)

[3] Liu L et al. Palaeogeogr. Palaeoclimatol. Palaeoecol. 391 (under review)