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We compared the stable carbon isotopic records from a loess transect of the Jiaochang in the eastern Tibetan Plateau,spanning the last～21,000 years,with multiproxy data for pedogenesis, including magnetic susceptibility,clay fraction,Fe_d/Fe_t ratio,carbonate and total organic carbon content,in order to probe the mechanisms ofδ~(13)C values of organic matter and Late Quaternary climate variations in the eastern Tibetan Plateau.Our results indicate that there is no simple relationship betweenδ~(13)C of organic matter and summer monsoon variations.The change inδ~(13)C values of organic matter(in accordance with the ratios of C_3 to C_4 plants)results from the interaction among temperature,aridity and atmospheric pCO_2 level.Drier climate and lower atmospheric pCO_2 level contribute to positive carbon isotopic excursion,while negative carbon isotopic excursion is the result of lower temperature and increased atmospheric pCO_2 level.Additionally,our results imply that the Tibetan monsoon may play an important role in climate system in the eastern Tibet Plateau, which specifically reflects frequently changing climate in that area.The results provide new insights into the forcing mechanisms on both theδ~(13)C values of organic matter and the local climate system.
We compared the stable carbon isotopic records from a loess transect of the Jiaochang in the eastern Tibetan Plateau, spanning the last ~ 21,000 years, with multiproxy data for pedogenesis, including magnetic susceptibility, clay fraction, Fe_d / Fe_t ratio, carbonate and total organic carbon content, in order to probe the mechanisms of δ ~ (13) C values of organic matter and Late Quaternary climate variations in the eastern Tibetan Plateau. Our results that that is no simple relationship between δ ~ (13) C of organic matter and summer monsoon variations. change in δ ~ (13) C values of organic matter (in accordance with the ratio of C_3 to C_4 plants) results from the interaction among temperature, aridity and atmospheric pCO_2 level. Carrier climate and lower atmospheric pCO_2 level contribute to positive carbon isotopic excursion, while negative carbon isotopic excursion is the result of lower temperature and increased atmospheric pCO_2 level. Additionally, our results imply that the Tibetan mons oon may play an important role in climate system in the eastern Tibet Plateau, which specifically reflects frequently changing climate in that area. The results provide new insights into the forcing mechanisms on both the delta ~ (13) C values of organic matter and the local climate system.