Temperature Controls on Diurnal Carbon Dioxide Flux
2003
Parkin, Timothy B. | Kaspar, Thomas C.
Carbon dioxide flux from the soil to the atmosphere is an important component of terrestrial C cycling, and accurate estimates of CO₂–C fluxes are critical in estimating C budgets. Accurate estimation of daily C loss from infrequent measurements of CO₂ flux requires characterization of the temporal variability associated with this processes. We investigated the relationships between diurnal CO₂ flux and temperature at two locations, corresponding to two soil types (a sandy loam and a clay loam) in a residue covered no-till corn (Zea mays L.)/soybean field (Glycine Max L. Merr.). Automated chambers provided hourly measurements of CO₂ flux from 4 Mar. through 6 June 2000. Hourly soil temperature measurements were made at the surface and at the 0.05-m depth, along with air temperature and soil water content measurements. Time series analysis showed that the temporal dynamics of CO₂ flux were more closely related to air temperature than to soil temperature, perhaps because a substantial portion of the CO₂ originated from surface residues. Exponential temperature correction algorithms (Q ₁₀) were evaluated using a range of Q ₁₀ factors applied to both air and soil temperatures. We found that a Q ₁₀ = 2 relationship when applied to a 0.05-m soil temperature performed poorly in this regard, however, air temperature based Q ₁₀ relationships (Q ₁₀ = 1.5 or 1.25) performed better in that they reduced time-of-day estimation biases from 28 to <4%. Knowledge of the efficacy of temperature correction algorithms and application of the appropriate temperature measurements should improve the accuracy of cumulative C flux estimates from short-term measurements.
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