Measurement of CO2 carbon Isotope fluxes from conventional and no-till agricultural fields

This paper presents the initial results of a study of CO₂ isotope flux measurements over tilled and no-till agricultural surfaces in Ontario, Canada. Measurements of CO₂ flux were obtained using both eddy covariance and flux-gradient micrometeorological techniques. Additionally, the flux-gradient measurements distinguished between C¹² and C¹³ - CO₂ isotope concentrations and fluxes. The current crop rotation at the site (alternating between C₃ and C₄ species) combined with detailed soil sampling will allow us to resolve temporal changes in substrate used for microbial respiration. Furthermore, independent measurements of CO₂ flux allow the calculation of turbulent transport coefficients which can be compared to those calculated using conventional wind-profile techniques. This paper will demonstrate some of these comparisons and show preliminary results of isotope flux measurements from conventionally-tilled and no-till plots during the spring thaw period.