Leaf carbon isotope composition of fossil and extant oaks grown under differing atmospheric CO₂ levels

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• 作者：Thanh Thuy Nguyen Tu ; Wolfram M. Kü ; rschner ; Stefan Schouten ; Pim F. Van Bergen
• 关键词：Leaf ; Oak ; pCO₂ ; Stable carbon isotopes
• 刊名：Palaeogeography, Palaeoclimatology, Palaeoecology
• 出版年：2004
• 出版时间：30 September 2004
• 年：2004
• 卷：212
• 期：3-4
• 页码：199-213
• 全文大小：320 K

文摘

The aim of this study is to investigate the effects of long-term variations in atmospheric CO₂ levels (pCO₂) on stable carbon isotope ratios in plants. Isotope measurements were undertaken on two kinds of oak leaves: fossil leaves originating from two Miocene levels of well-documented and differing pCO₂ (i.e., 280 and 360 ppmv), and extant leaves of the same species coming from plants experimentally grown under contrasted pCO₂. Measurements were performed separately on sun and shade leaves to avoid bias linked to leaf morphotype, and on bulk leaves and individual n-alkanes extracted from the leaves, to detect possible diagenetic alteration of the isotope signal. Although extant oaks exhibit no significant trend in isotope discrimination with varying pCO₂, fossil oaks from the high pCO₂ level tend to exhibit slightly smaller isotope discrimination than those from the low pCO₂ level. However, the difference in fossil discrimination is only of 0.5‰ and its origin cannot be unequivocally assessed since other environmental parameters could be responsible for it. Therefore, it appears that if plant carbon isotope composition is sensitive to long-term pCO₂ variations, its response is rather minimal.