HR: 0800h
AN: B51D-0236    [Abstracts]
TI: Using the Carbon Isotope Ratios of Bison Tooth Enamel and Bone Collagen as a Quantitative Proxy for Reconstructing Grassland Vegetation and Paleotemperatures
AU: * Hoppe, K A
EM: hoppe@ess.washington.edu
AF: Dept. of Earth and Space Sci., Univ. of Washington, Seattle, WA 98195-1310
AU: Paytan, A
EM: apaytan@pangea.Stanford.EDU
AF: Dept. of Geological and Environmental Sci., Stanford Univ., Stanford, CA 94305-2115
AU: Chamberlain, P
EM: chamb@pangea.stanford.edu
AF: Dept. of Geological and Environmental Sci., Stanford Univ., Stanford, CA 94305-2115
AB: The carbon isotope ratios of tissues from grazing herbivores reflect the average carbon isotope ratios of local grasslands, which vary with the abundance of cool-season (C-3) versus warm-season (C-4) grasses. Since the C-3/C-4 ratios of grasslands correlate with climate, the carbon isotope ratios of fossil grazers may serve as a proxy for reconstructing paleovegetation and paleoclimatic conditions. Analyses of fossil and subfossil bison hold particular promise for use as a proxy for paleoenvironmental conditions in North America because bison remains are abundant in Holocene and Pleistocene deposits across most of the continent. However, the accuracy and precision of paleoenvironmental reconstructions based on bison is currently uncertain because the relationship between bison isotope and the abundance of C-3 and C-4 grasses has not been precisely quantified across different environments. We have analyzed the carbon isotope ratios of tooth enamel carbonate and bone collagen from 88 modern free ranging bison ( Bison bison) from ten locations in the Central United States. The C-4 biomass at these locations ranged from less than 1 percent to 95 percent of the total grass biomass. The mean carbon isotope ratios of enamel for each population correlated well with the local abundance of C-4 grasses (R2 = 0.93, p = 0.0001) and with variations in mean annual temperatures (R2 = 0.83, p = 0.001). The mean carbon isotope ratios of collagen for each population also correlated well with the C-4 grass abundance (R2 = 0.97, p = 0.0001) and mean annual temperature (R2 = 0.84, p = 0.0002). Enamel and collagen display similar variability (mean standard deviation = 0.7 per mil), and the variability does not change with climate, habitat, or C-4 abundance. These results demonstrate that analyses of the carbon isotope ratios of fossil bison can be used as a quantitative proxy for reconstructing grassland C-3/C-4 ratios and paleotemperatures, and they will serve as a baseline for interpreting isotopic analyses of fossil bison and other large herbivores from North America.
DE: 0400 BIOGEOSCIENCES
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0491 Food webs and trophodynamics (4817)
SC: Biogeosciences [B]
MN: Fall Meeting 2005