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Objective 1 |
Objective 1. Produce new calculations of mean annual temperature from the existing leaf collections and improved regression models that use leaf physiognomy. Bailey and Sinnott (1915, 1916) recognized a strong relationship between temperature and the percentage of dicot species within a flora that have leaves with entire margins. Wolfe (1979) established a linear regression of MAT vs. the percentage of dicot species with entire margins for Asian forests and generalized and improved the model by using a multivariate approach called Climate-Leaf Analysis Multivariate Program (CLAMP; Wolfe 1993). Wilf (1997) recently demonstrated that the temperature signal is dominated by the leaf-margin character in the multivariate approach and suggested using a univariate rather than a multivariate approach. We propose to use the Wilf (1997) model, and the leaves of the Eocene taxa to calculate MAT as one estimate of paleotemperature. Stable Isotopes We propose to use stable isotope techniques to estimate d 13C value of the Eocene atmosphere, the d 18O and d D values of paleoprecipitation at the site, site mean annual temperature (MAT), site growing season temperatures, and pCO2 of the Eocene atmosphere. In addition we propose to use isotopes to inform us about the following paleoecological parameters: water-stress differences between age classes of Metasequoia at each site, water-stress differences between different taxa on each site, and variation within a taxon between sites, and taxonomic contributions to ecosystem productivity via paleosol isotopic composition. Since Metasequoia (and to a lesser extent Glyptostrobus) was planted widely in arboreta during the first half of this century, we have the opportunity to make isotopic measurements on the mummified wood and on extant, mature individuals growing in a variety of temperature and soil moisture regimes. This is expected to provide useful calibration for interpreting the isotope data obtained from the Eocene samples. |