HR: 14:55h
AN: B13B-06    [Abstracts]
TI: Allocation of Recent Photosynthetic Products Using a Dual Isotope (13C and 14C) Pulse-Chase Labeling Technique
AU: * Carbone, M S
EM: mcarbone@uci.edu
AF: Department of Earth System Science, University of California, Irvine, 3200 Croul Hall, Irvine, CA 92697-3100
AU: Trumbore, S
EM: setrumbo@uci.edu
AF: Department of Earth System Science, University of California, Irvine, 3200 Croul Hall, Irvine, CA 92697-3100
AU: McDuffee, K
EM: kmcduffe@uci.edu
AF: Department of Earth System Science, University of California, Irvine, 3200 Croul Hall, Irvine, CA 92697-3100
AU: Xu, X
EM: xxu@uci.edu
AF: Department of Earth System Science, University of California, Irvine, 3200 Croul Hall, Irvine, CA 92697-3100
AB: Pulse-chase labeling studies provide a non-destructive way to follow the allocation of recent photosynthetic products to above and belowground plant pathways. In August 2005, we applied a CO2 label enriched in 13C and low-levels of 14C, to elucidate differences in carbon allocation patterns between two plant communities (perennial grasses and shrubs) in the Owens Valley, CA. Following the label application, we sampled the CO2 flux and isotopic content of respiration from the leaves and stems, the soil surface, the soil profile, and the total ecosystem. The 13C signal was intended to quantify allocation to fast cycling respiration pathways (<6 days), where as the 14C signal was designed to follow the fate of the label into longer-lived plant carbon pools including respiration, growth, and storage (>6 days). The low-level 14C label was measured by accelerator mass spectrometry (AMS), and had radioactivity levels below what is classified as harmful or hazardous waste. This combination of stable and radiocarbon isotope tracers allowed us to safely label in the field, at ambient CO2 concentrations, yet minimize the expense of AMS analyses. Our preliminary 13C results show differences in the depth distribution and persistence of the label in the soil CO2 between the grass and shrub communities. The 14C results show that the label signal is still measurable in respiration four weeks after labeling. We believe this application will provide valuable insight into carbon cycling, particularly belowground, where carbon used for root respiration, growth, and storage are not easily observed nor well quantified.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005