Effect of Warming and Elevated O(3) Concentration on CO(2) Emissions in a Wheat-Soybean Rotation Cropland

A deeper understanding of the effects of experimental warming and elevated ozone (O(3)) concentration on carbon dioxide (CO(2)) fluxes is imperative for reducing potential CO(2) emissions in agroecosystems, but are less understood particularly in rotational wheat (Triticum aestivum)—soybean (Glycine max) croplands. In order to understand such effects on CO(2) fluxes from winter wheat-soybean rotation, a field experiment was conducted by using the open-top chamber (OTCs) during the growing seasons of 2012 and 2013 at an agro-ecological station in southeast China. The experimental treatments included the control (CK), experimental warming (T, crop canopy temperature increased by ~2 °C), elevated O(3) concentration (O, O(3) concentration about 100 ppb) along with temperature enhancement (OT, elevated ~2 °C temperature plus 100 ppb O(3)). The results showed that warming significantly increased the mean CO(2) fluxes (MCF) and the cumulative amount of CO(2) (CAC) from soil and soil-crop systems, while elevated O(3) and warming enhancement (OT) significantly reduced MCF and CAC. Besides, warming significantly reduced the biomass of winter-wheat, but it insignificantly decreased the biomass of soybean in the harvest period. The O and OT treatments significantly reduced the biomass of winter-wheat and soybean cropping systems in the harvest time. Both warming and elevated O(3) concentration decreased the temperature sensitivity coefficients (Q(10)) in soil respiration during the experimental period. Overall, our results indicate that elevated O(3) concentration compensates the effect of warming on CO(2) emission to some extents, which has a positive feedback impact on the climate system.