JP1.2 Carbon isotope signature of soil respiration from agricultural fields: late fall and spring measurements in Ontario, Canada

Tuesday, 29 April 2008
Floral Ballroom Magnolia (Wyndham Orlando Resort)
Selma R. Maggiotto, University of Guelph, Guelph, ON, Canada; and C. Wagner-Riddle, J. Warland, and G. Drewitt

Measurements of the isotopic signature of CO2 fluxes from conventional and no-till areas were carried out during fall 2005 to spring 2006, and will be on-going over fall 2007 to spring 2008, in Ontario, Canada. Concentrations of 12C- and 13C-CO2 isotopes were measured using a tunable diode laser trace gas analyzer. The d13C of soil respiration was then used to compare the proportion of C originating from crop residue (corn, a C4 plant) vs. soil organic matter (formed predominantly from C3 plants), in no-till and conventional plots. Results from 2005/2006 indicate more rapid decomposition of the ‘newly-added' residue in the conventional tillage treatment, with a stronger C4 signature (-16.7 ± 2.5‰) compared to the no-till field (-20.2±2.7‰). These results will be compared to recent measurements at the same site.
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