【摘要】 对甘肃临夏塬堡全新世黄土剖面古土壤有机质碳同位素的分析表明,δ13C变化范围在-28.23‰～-25.19‰之间,平均值为-26.88‰。结合该剖面孢粉以及地层研究结果,观察到在温暖湿润气候期间,δ13C表现为高值,而在干燥寒冷期间,δ13C表现为低值,这较好地反映了该地区全新世气候演化的历史。结合其他研究,认为黄土高原地区全新世地表植被中草本植物C3和C4植物比例的变化是引起土壤有机质δ13C变化的直接原因,由于气候变化引起了地表植被类型的改变,古土壤中有机质δ13C发生了变化。对比塬堡剖面与西安、旬邑剖面土壤有机质的δ13C,观察到西安和旬邑两剖面的δ13C平均值要高于塬堡剖面约5‰左右,这是由于全新世期间两地气候的暖湿程度要高于临夏地区,地表植被中喜暖湿气候的C4植物比例较高,导致土壤有机质δ13C增大。因此δ13C是研究古气候变化的一个较好的手段。更多还原

【Abstract】 The values of δ13C of organic matters in the paleosol from the Yuanbao Holocene profile, Linxia, Gansu Province are between -28.23‰to -25.19‰, with an average of -26.88‰. Combining with the pollen and stratum records at the same profile, it is shown that high δ13C are corresponding to warm and humid climate, and low to cold and arid climate, which means that the δ13C of organic matters in the paleosol can reflect the Holocene climatic evolution at the study area by recovering the vegetation change. With other research conclusions, it is confirmed that the ratio variation of C3 and C4 of the surface plants mainly affected the δ13C change of organic matters in the paleosol, and climate change resulted change of the vegetation type and the carbon isotope composition. Comparing the δ13C researches from the Xian and Xunyi profiles, Shaanxi Province, the δ13C average values at the two profiles are about 5‰higher than that at the Yuanbao profile, suggesting higher temperature and precipitation occurred at Xian and Xunyi during Holocene. It is concluded that the carbon isotope composition of organic matter in the paleosol is also an indicator for the paleoclimatic change.更多还原