Stomatal Density and Index of Fossil Plants Track Atmospheric Carbon Dioxide in the Palaeozoic

Mesozoic ecosystems – climate and biotas

“…The authors use fossil laurel leaf cuticles recovered from three New Zealand assemblages, which collectively span the latest Cretaceous to mid-Paleocene. Leaf cuticles are commonly used to reconstruct atmospheric carbon dioxide concentrations (pCO 2 ) by applying stomatal density analysis, which was first developed by McElwain and Chaloner (1995) and this method is employed by Steinthorsdottir et al (2016). The results, which represent the first Southern Hemisphere stomatal density data spanning the K-Pg boundary, are consistent with previously published pCO 2 records from the Northern Hemisphere.…”

Stomatal density and stomatal index as indicators of paleoatmospheric CO2 concentration

“…Estimating pre-Cretaceous CO 2 levels proves more dif®cult. McElwain and Chaloner (1995) developed a technique comparing responses of fossil species to those of their Nearest Living Equivalents (NLEs). NLEs are de®ned ecologically, not taxonomically, and represent the ecologically closest living analog to the fossil species.…”

“…6. Estimates of CO 2 for the Devonian, Carboniferous±Permian, Triassic, Jurassic, and Eocene (unmarked boxes) calculated from the stomatal ratio technique of McElwain and Chaloner (1995) superimposed over the CO 2 curve and corresponding error envelope of Berner (1994Berner ( , 1998. Stomatal ratio scale calibrated to RCO 2 scale using a 1:1 correspondence; this is the`Recent standard ' of McElwain (1998).…”

“…Estimates from stomatal indices have the potential to help resolve this question. As for pre-Cretaceous estimates, the less quantitative stomatal ratio method of McElwain and Chaloner (1995) …”

“…The proportion of fossil responses showing an inverse relationship based on subambient CO 2 exposure are nearly equal to those fossil observations based on elevated CO 2 exposure for both SD (89 and 100%, respectively) and SI (89 and 96%, respectively), although sample sizes are fairly small (Table 1). Some groups of plants respond to CO 2 levels of at least 2700 ppmV (McElwain and Chaloner, 1995;Appendix C). This result does not discount, however, that stomatal parameters may be less sensitive at elevated than at subambient (relative to today) CO 2 levels.…”