Leaf carbon isotope compositions and stomatal characters: important considerations for palaeoclimate reconstructions

Variations in stable carbon isotope composition and stomatal characters of fossil leaves are being used increasingly to provide information about pala eoatmospheric CO2 concentrations. However, differences in these parameters are not solely dependant on CO2 concentrations and factors such as aspect ( i.e. sun and shade) must be considered in palaeoenvironmental reconstructio ns. Stable carbon isotope analyses in combination with stomatal analyses of canopy sun and shade leaves of modern Fugus sylvatica reveal that sun leav es contain more C-13 and have higher stomatal indices when compared with sh ade leaves. These observations, probably related to stomatal conductance, h ave significant implications for studies using fossil leaves to reveal pala eoclimate signals. (C) 1998 Elsevier Science Ltd. All rights reserved.