HR: 10:20h
AN: PP22A-01    [Abstracts]
TI: Hydrogen Isotopes From Tree Leaves: Evaluation of Environmental and Phenotypic Controls
AU: * Pedentchouk, N
EM: nikolai.pedentchouk@yale.edu
AF: Department of Geology and Geophysics Yale University, P.O. Box 208109 , New Haven, CT 06520 United States
AU: Pagani, M
EM: mark.pagani@yale.edu
AF: Department of Geology and Geophysics Yale University, P.O. Box 208109 , New Haven, CT 06520 United States
AU: McElwain, J
EM: mcelwain@fieldmuseum.org
AF: Department of Geology, The Field Museum, 1400 S. Lake Shore Dr., Chicago, IL 60605 United States
AU: Vitousek, P
EM: vitousek@stanford.edu
AF: Stanford University, Herrin Labs 498A, Stanford, CA 94305 United States
AU: Chadwick, O
EM: oac@geog.ucsb.edu
AF: University of California, Santa Barbara, Santa Barbara, CA 93106 United States
AB: D/H composition of terrestrial plant lipids is a new tool that has the potential to provide information about paleoclimate. To assess the robustness of the link between D/H of leaf wax lipids and environmental parameters we analyzed n-alkanes from 150 Quercus kelloggii leaves in California and 70 Metrosideros polymorpha leaves from the Big Island of Hawaii. Samples were collected from trees throughout strong climatic gradients. The nC29-alkane isotopic data from Quercus kelloggii in California show two major trends. First, samples close to the coast are D-enriched relative to those in the Sierra Nevada, averaging minus 174 per mil and minus 185 per mil, respectively. Second, samples from northwestern California are D-depleted in comparison with those from the southeast, averaging minus 195 per mil and minus 170 per mil. In order to investigate the source of these differences we compared D/H of nC29 in Quercus kelloggii with D/H of precipitation and other environmental parameters. Principal Component Analysis shows that D/H composition of precipitation is linked to D/H of nC29 stronger than any other parameter. The D/H of nC29 alkanes along the coast - Sierra Nevada transect show a good correlation with D/H of precipitation: R2 = 0.54. However, the relationship between these two variables along the northwest - southeast transect is less robust: R2 = 0.33. Qualitative assessment of the relationship between D/H of nC29 and the relative humidity suggests a negligible effect of this parameter along the coast - Sierra Nevada transect, since the coastal sites with a high relative humidity are characterized by D-enrichment. The importance of relative humidity on the distribution of D/H values of nC29 along the northwest - southeast transect, however, is likely to be a major factor, since samples from the relatively wet northwestern California are generally D-depleted in comparison with those in the drier southeast. Preliminary data from Hawaii indicate that D/H values of n-alkanes from Metrosideros polymorpha are poor recorders of D/H and amount of precipitation. Superimposed phenotypic and biochemical variations among different polymorphic varieties of this species are perhaps the main reason for this observation. The results of this study will provide an opportunity to compare the strength of the relationship between D/H composition of tree leaf biomarkers and environmental parameters in physiographically different plant species: continental Quercus kelloggii in California and Metrosideros polymorpha indigenous to an isolated system of Hawaiian Islands.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1637 Regional climate change
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4914 Continental climate records
DE: 4994 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005