Stable Carbon Isotopic Composition of Black Carbon in Surface Soil as a Proxy for Reconstructing Vegetation on the Northern Slope of the Qinling Mountains

摘要

Because of the unique geographical location and important ecological effect of the Qinling Mountains,reconstruction of its vegetation and climate needs comprehensive research.We need to consider a multiple-proxy approach to gain more information on recovering the paleovegetation and climate in the Qinling Mountains.Black carbon(BC)is produced by the incomplete combustion of vegetation and fossil fuels,and is a good proxy,recording paleoenvironmental information.However,in the Qinling Mountains,what are the characteristics of the BC,and whether BC stable carbon isotope(δ^(13)C_(BC))can be used as a new proxy to study ancient vegetation,still need further study.In order to establish a sound basis for studying paleoenvironmental by BC proxy in the Qinling Mountains,we carried out systematic and detailed study on modern process of BC on the northern slope of the mountains.We analyzed stable carbon isotopes and carbon concentration of organic carbon(%SOC,δ^(13)C_(SOC))and BC(%BC,δ^(13)C_(BC)),and identified the pollen assemblages from systematically sampled surface soil.The results show that the calculated ratio of C_4 plants in the vegetation(%C_4)based on theδ^(13)C_(SOC)data reflects a similar distribution of C_4 plants in the surface vegetation and the pollen assemblage.Theδ^(13)C_(BC)values have a strong positive correlation withδ^(13)C_(SOC)values,and their difference(△^(13)C_(SOC-BC))is in the low range.These data indicate thatδ^(13)C_(BC)andδ^(13)C_(SOC)have very similar characteristics.Surface soilδ^(13)C_(BC)values can indicate surface vegetation as effectively asδ^(13)C_(SOC)values,and theδ^(13)C_(BC)proxy can be used effectively in paleovegetational research in the northern slope of Qinling Mountains.