Does δ¹³C_carb of the Chinese loess indicate past C₃/C₄ abundance? A review of research on stable carbon isotopes of the Chinese loess

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• 作者：Zhiguo Rao ; Zhaoyu Zhu ; Fahu Chen and Jiawu Zhang
• 刊名：Quaternary Science Reviews
• 出版年：2006
• 出版时间：September 2006
• 年：2006
• 卷：25
• 期：17-18
• 页码：2251-2257
• 全文大小：361 K

文摘

Current research on stable carbon isotopes of the Chinese loess is reviewed. The stable carbon isotopic composition of soil organic matter (SOM) (δ¹³C_org) of paleosols formed during interglacials is more positive than that within loess accumulated during glacials. Spatially, it becomes progressively more negative from the eastern Chinese Loess Plateau (CLP) to the western. However, stable carbon isotopic composition of pedogenic carbonates (δ¹³C_carb) from the same sequence produces an opposing trend, both temporally and spatially, and variation differs from expectations under conditions of equilibrium. This indicates that δ¹³C_carb in the Chinese loess cannot be used to reconstruct the relative proportion of C₃/C₄ plants in past ecological communities. Furthermore, use of δ¹³C_carb to reconstruct the expansion of C₄ plants in older Tertiary red clay deposits is considered unreliable. We believe δ¹³C_carb may act as an indirect indicator of vegetation density, following on changes in moisture supply controlled by the intensity of the Asian Summer Monsoon, but conclude that full understanding of the paleoclimatic significance of δ¹³C_carb in the Chinese loess and underlying Tertiary red clay requires better understanding of modern isotopic processes.