Articles | Volume 12, issue 2
https://doi.org/10.5194/cp-12-241-2016
https://doi.org/10.5194/cp-12-241-2016
Research article
 | 
10 Feb 2016
Research article |  | 10 Feb 2016

Estimates of late middle Eocene pCO2 based on stomatal density of modern and fossil Nageia leaves

X. Y. Liu, Q. Gao, M. Han, and J. H. Jin

Abstract. Atmospheric pCO2 concentrations have been estimated for intervals of the Eocene using various models and proxy information. Here we reconstruct late middle Eocene (42.0–38.5 Ma) pCO2 based on the fossil leaves of Nageia maomingensis Jin et Liu collected from the Maoming Basin, Guangdong Province, China. We first determine relationships between atmospheric pCO2 concentrations, stomatal density (SD) and stomatal index (SI) using “modern” leaves of N. motleyi (Parl.) De Laub, the nearest living species to the Eocene fossils. This work indicates that the SD inversely responds to pCO2, while SI has almost no relationship with pCO2. Eocene pCO2 concentrations can be reconstructed based on a regression approach and the stomatal ratio method by using the SD. The first approach gives a pCO2 of 351.9 ± 6.6 ppmv, whereas the one based on stomatal ratio gives a pCO2 of 537.5 ± 56.5 ppmv. Here, we explored the potential of N. maomingensis in pCO2 reconstruction and obtained different results according to different methods, providing a new insight for the reconstruction of paleoclimate and paleoenvironment in conifers.

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Short summary
We reconstruct late middle Eocene (42.0–38.5 Ma) pCO2 based on the fossil leaves of Nageia maomingensis Jin et Liu collected from the Maoming Basin, Guangdong Province, China. This work indicates that the stomatal density (SD) inversely responds to pCO2, while stomatal index (SI) has almost no relationship with pCO2, using "modern" leaves of N. motleyi (Parl.) De Laub. Regression approach gives a pCO2 of 351.9 ± 6.6 ppmv, whereas stomatal ratio method gives a pCO2 of 537.5 ± 56.5 ppmv.