HR: 0800h
AN: B41C-0645    [Abstracts]
TI: Analysis of Changes in Biochemical Composition Under Free-Air CO₂ enrichment by ¹³C Nuclear Magnetic Resonance: Leaf Litter, Roots, and Soils From Oak Ridge
AU: * Hockaday, W C
EM: bill.hockaday@rice.edu
AF: Rice University, Department of Earth Science, P.O. Box 1892, Houston, TX 77251, United States
AU: Masiello, C A
EM: masiello@rice.edu
AF: Rice University, Department of Earth Science, P.O. Box 1892, Houston, TX 77251, United States
AU: Baldock, J A
AF: CSIRO Land and Water, PMB #2, Glen Osmond, SA 5064, Australia
AU: Iversen, C M
EM: civersen@utk.edu
AF: University of Tennessee, Department of Ecology and Evolutionary Biology, 569 Dabney Hall, Knoxville, TN 37996, United States
AU: Norby, R J
EM: rjn@ornl.gov
AF: Oak Ridge National Lab, One Bethel Road, Building 1062, Oak Ridge, TN 37831, United States
AB: Changes in plant biochemistry as a result of increasing atmospheric carbon dioxide concentration [CO₂] influence the cycling of the terrestrial carbon pool and thereby constitute a climate feedback. We have investigated molecular-level changes in the chemical composition of the organic carbon pool of a deciduous forest in Oak Ridge, Tennessee, after 9 years of free-air CO₂ enrichment. We employ a novel approach based upon solid-state ¹3C nuclear magnetic resonance (NMR) analysis and application of a molecular mixing model. This method generates quantitative estimates of total lipids, proteins, carbohydrates, and lignin. ¹³C NMR spectra were acquired for acid-insoluble soil organic matter from depths of 0 – 5 cm and 5 – 15 cm in two ambient and two elevated [CO₂] treatments. In the upper 5 cm, elevated [CO₂] soils show a 7% increase in lignin, while lipids and proteins decrease by approximately 10%. Below 5 cm, soil lipid content decreased by 15% relative to ambient [CO₂] soils. Changes in the composition of the SOM pool may be attributed to changes in plant biochemistry under elevated [CO2]. Therefore we have performed ¹³C NMR analysis of major aboveground and belowground biomass inputs: senesced leaves and fine roots (<1 mm diameter). Significant [CO₂] effects on root chemistry are observed. Based upon these data, we are able to make a preliminary assessment of the contributions of leaf C and root C to changes in the molecular composition of the SOM pool.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 1694 Instruments and techniques
SC: Biogeosciences [B]
MN: 2007 Fall Meeting