HR: 1340h
AN: B43D-1591    [Abstracts]
TI: Accuracy and Precision in Measurements of Biomass Oxidative Ratio and Carbon Oxidation State
AU: * Gallagher, M E
EM: megirish@rice.edu
AF: Dept. of Earth Science, Rice University, 6100 Main St. MS-126, Houston, TX 77005, United States
AU: Masiello, C A
EM: masiello@rice.edu
AF: Dept. of Earth Science, Rice University, 6100 Main St. MS-126, Houston, TX 77005, United States
AU: Randerson, J T
EM: jranders@uci.edu
AF: Dept. of Earth System Science, University of California-Irvine, 3212 Croul Hall, Irvine, CA 92697, United States
AU: Chadwick, O A
EM: oac@geog.ucsb.edu
AF: Dept. of Geography, University of California - Santa Barbara, Girvetz 2308, Santa Barbara, CA 93106, United States
AU: Robertson, G P
EM: robertson@kbs.msu.edu
AF: W.K. Kellogg Biological Station an the Dept. of Crop and Soil Sciences, Michigan State University, 3700 East Gull Lake Drive, Hickory Corners, MI 49060, United States
AB: Ecosystem oxidative ratio (OR) is a critical parameter in the apportionment of anthropogenic CO₂ between the terrestrial biosphere and ocean carbon reservoirs. OR is the ratio of O₂ to CO₂ in gas exchange fluxes between the terrestrial biosphere and atmosphere. Ecosystem OR is linearly related to biomass carbon oxidation state (C_ox), a fundamental property of the earth system describing the bonding environment of carbon in molecules. Cox can range from -4 to +4 (CH₄ to CO₂). Variations in both C_ox and OR are driven by photosynthesis, respiration, and decomposition. We are developing several techniques to accurately measure variations in ecosystem C_ox and OR; these include elemental analysis, bomb calorimetry, and ¹³C nuclear magnetic resonance spectroscopy. A previous study, comparing the accuracy and precision of elemental analysis versus bomb calorimetry for pure chemicals, showed that elemental analysis-based measurements are more accurate, while calorimetry- based measurements yield more precise data. However, the limited biochemical range of natural samples makes it possible that calorimetry may ultimately prove most accurate, as well as most cost-effective. Here we examine more closely the accuracy of C_ox and OR values generated by calorimetry on a large set of natural biomass samples collected from the Kellogg Biological Station-Long Term Ecological Research (KBS-LTER) site in Michigan.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0452 Instruments and techniques
DE: 1600 GLOBAL CHANGE
SC: Biogeosciences [B]
MN: 2007 Fall Meeting