Search for: All records

Abstract PremiseMechanistic models using stomatal traits and leaf carbon isotope ratios to reconstruct atmospheric carbon dioxide (CO₂) concentrations (c_a) are important to understand the Phanerozoic paleoclimate. However, methods for preparing leaf cuticles to measure stomatal traits have not been standardized. MethodsThree people measured the stomatal density and index, guard cell length, guard cell pair width, and pore length of leaves from the sameGinkgo biloba,Quercus alba, andZingiber miogaleaves growing at known CO₂levels using four preparation methods: fluorescence on cleared leaves, nail polish, dental putty on fresh leaves, and dental putty on dried leaves. ResultsThere are significant differences between trait measurements from each method. Modeledc_acalculations are less sensitive to method than individual traits; however, the choice of assumed carbon isotope fractionation also impacted the accuracy of the results. DiscussionWe show that there is not a significant difference betweenc_aestimates made using any of the four methods. Further study is needed on the fractionation due to carboxylation of ribulose bisphosphate (RuBP) in individual plant species before use as a paleo‐CO₂barometer and to refine estimates based upon widely applied taxa (e.g.,Ginkgo). Finally, we recommend that morphological measurements be made by multiple observers to reduce the effect of individual observational biases.