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Carbon dioxide fluxes in cornâsoybean rotation in the midwestern U.S.: Inter- and intra-annual variations, and biophysical controls
- Hernandez-Ramirez, Guillermo, Hatfield, Jerry L., Parkin, Timothy B., Sauer, Thomas J., Prueger, John H.
- Agricultural and forest meteorology 2011 v.151 no.12 pp. 1831-1842
- eddy covariance, planting date, soil organic carbon, seasonal variation, soil respiration, biogeochemical cycles, additive effect, carbon dioxide, soil heterogeneity, ambient temperature, ecosystems, photosynthesis, land use change, Zea mays, Glycine max, soil water content, air temperature, corn, climate change, hysteresis, crop rotation, soybeans, growing season, crops, Iowa
- Quantifying carbon dioxide (COâ) fluxes in terrestrial ecosystems is critical for better understanding of global carbon cycling and observed changes in climate. This study examined year-round temporal variations of COâ fluxes in two biennial crop rotations during 4 year of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production. We monitored COâ fluxes using eddy-covariance (EC) and soil chambers in adjacent production fields near Ames, Iowa. Under the non-limiting soil water availability conditions predominant in these fields, diel and seasonal variations of COâ fluxes were mostly controlled by ambient temperature and available light. Air temperature explained up to 81% of the variability of soil respiratory losses during fallow periods. In contrast, with full-developed canopies, available light was the main driver of daytime COâ uptake for both crops. Furthermore, a combined additive effect of both available light and temperature on enhanced COâ uptake was identified only for corn. Moreover, diurnal hysteresis of net COâ uptake with available light was also found for both crops with consistently greater COâ uptake in the mornings than afternoons perhaps primarily owing to delay in peak of soil respiration relative to the time of maximum plant photosynthesis. Annual cumulative COâ exchange was mainly determined by crop species with consistently greater net uptake for corn and near neutral exchange for soybean (â466Â±38 and â13Â±39gCmâ»Â²yearâ»Â¹). Concomitantly, within growing seasons, COâ sink periods were approximately 106 days for corn and 90 days for soybean, and peak rates of COâ uptake were roughly 1.7-fold higher for corn than soybean. Apparent changes in soil organic carbon estimated after accounting for grain carbon removal suggested soil carbon depletion following soybean years and neutral carbon balance for corn. Overall, results suggest changes in land use and cropping systems have a substantial impact on dynamics of COâ exchange.