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黄土高原地质历史时期原生植被类型,C3/C4植物的时空演化规律等,一直是黄土研究中争论较多的问题,而黄土剖面元素碳碳同位素(δ13Cec)记录可能为植被演替变化提供新的依据.元素碳(EC)是植被不完全燃烧的产物,其碳同位素较先体植被变化很小,从而可利用δ13Cec记录反演植被变化.采用化学氧化法提取黄土高原中部灵台剖面黄土-古土壤序列中的EC物质,并进行δ13Cec分析.结果表明,该地区为C3,C4植物混合植被类型,大多数时段以C3植物为主.晚第四纪以来,黄土高原C3,C4植物变化可能并不遵循简单的冰期-间冰期旋回变化模式,而是呈现波动变化:L4时期C3植物逐渐增多,S3时期C3植物较多;L3～L2时期C4植物增多;S1～S0时期C3植物再次增多.在古土壤发育时期中,S3,S1时期C3植物较多,S2和S0时期C4植物相对较多.在黄土堆积时期中,L4和L1时期C3植物较多,L3和L2时期C4植物相对较多.在冰期-间冰期旋回尺度上,δ13Cec揭示的植被变化与孢粉资料得到的结果较为一致;与有机碳碳同位素(δ13Corg)所揭示的植被变化仅在末次冰期以来的时期较为一致.
The proto-vegetation types in the geological history of the Loess Plateau and the temporal and spatial evolution of C3 / C4 plants have always been the subject of much debate in the loess research. However, the δ13Cec records of loess sections may provide new information on vegetation succession changes Based on the fact that elemental carbon (EC) is a product of incomplete combustion of vegetation, its carbon isotopic composition is less changed than that of its precursor so that the δ13Cec record can be used to reverse the change of vegetation.The chemical oxygenation method was used to extract loess-paleosol from the Lingtai section in the central part of the Loess Plateau And the results of δ13Cec analysis showed that the region was dominated by C3 and C4 plant types and most of the time were C3 plants.The C3 and C4 plants in the Loess Plateau may not change since the late Quaternary Followed by a simple glacial-interglacial cycle variation pattern, but fluctuated: C3 plants gradually increased in L4, more C3 plants in S3, C4 plants increased in L3 ~ L2, and C3 plants increased again in S1 ~ S0. During the period of soil development, there were more C3 plants in S3 and S1 periods and more C4 plants in S2 and S0 periods, while there were more C3 plants in L4 and L1 and more C4 plants in L3 and L2 during soil accumulation. ice The results of δ13Cec revealed the same vegetation change as the sporopollen data in the Mesozoic-interglacial cycles. The changes of vegetation revealed by δ13Corg are consistent only with the period since the last glacial period.