HR: 1340h
AN: PP43B-1260    [Abstracts]
TI: Orographic and Climatic Influence on Leaf Wax Carbon and Hydrogen Isotopic Ratios: a Field Survey From Northern California
AU: * Tipple, B J
EM: brett.tipple@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave, New Haven, CT 06520, United States
AU: Pagani, M
EM: mark.pagani@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave, New Haven, CT 06520, United States
AU: Smith, R
EM: ronald.smith@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave, New Haven, CT 06520, United States
AU: Anders, A
EM: amanders@uiuc.edu
AF: University of Illinois, Department of Geology, 1301 W. Green St., Urbana, IL 61801, United States
AB: The primary objective of this research was to empirically ground-truth environmental controls on δD and δ¹³C values of higher plant n-alkanes, since these higher-plant specific compounds are refractory and commonly preserved in the geologic record they hold great paleoclimatic and paleoenvironmental information. Our approach was to extensively sample leaves and stems of nine species of trees across two Northern California east-west transects twice during the growing season. One hundred and ninety trees from ninety-three sites were collected along with topsoils and surface waters from most localities. Bigleaf Maple ( Acer macrophyllum), California White Oak ( Quercus lobata) and Blue Oak ( Quercus douglasii) n--alkanes δ¹³C have been analyzed and range from -38.0 to -29.6‰, -35.2 to - 30.4‰ and -34.5 to -30.4‰, respectively. Currently, all tree species show little to no relationship with any physical variable, such as longitude, elevation, tree height, aspect, slope, etc. The large range in tree isotope values suggests these plants are reacting to a yet unknown climatic variable or these species operate within a range of water-use efficiencies. Similarly, soil-extracted n--alkane δ¹³C values range between -36.5 to -29.2‰ and do not strongly correlate with any physical parameter. Surface water δD and δ¹⁸O are highly correlated and similar to the meteoric water line, however, not as robust, soil-extracted n--alkane δD show similar trends. Notably, the apparent enrichment factor between soil lipids and surface waters is not as stable as seen in other localities, varying by over 30‰, illustrating uncertainties in paleo-applications. Interestingly, water δD and δ¹⁸O from surface waters varied little between early June and mid-September and demonstrate a roughly -90‰ depletion in deuterium across the two transects. This D-depletion is reflected in the early growing season stem waters with a consistent slope to that of surface waters.
DE: 0424 Biosignatures and proxies
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0476 Plant ecology (1851)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1055 Organic and biogenic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting