Effect Of Simulated Experimental Warming And Elevated O₃on N₂O Emission, Nitrification And Denitrification Rates In A Cropland

Winter-wheat and soybean, conventional crops in China were selected as the experimental material in our study. A soybean growing season and a winter-wheat growing season experiments were carried out in farmland. Open top chamber(OTC) were used to increase ozone concentration, and infrared radiation lamps were used for experimental warming. Four different treatments were set up, including the control (CK), experimental warming (T, leaf temperature rised1.5℃), elevated O3(O, ozone concentration100nL/L), experimental warming+elevated O3(OT, leaf temperature rised1.5℃+ozone concentration100nL/L). N2O emission fluxes were analyzed by a static chamber-gas chromatograph method, and the gross nitrification (Gn) and denitrification rates (D) were determined using BaPS. In this study, the soil temperature and humidity instrument was used to observe soil temperature and soil moisture while collecting the gas in the field, crop biomass and leaf nitrate reductase were measured in important growth stages. Furthermore, the effects of experimental warming and elevated ozone on N2O emission fluxes and soil Gn-D were investigated. Results indicated that:During winter wheat growing season, experimental warming and elevated O3did not change the seasonal variation pattern of N2O emission fluxes from soil-wheat system and soil. Compared with CK, T treatment significantly increased N2O emission fluxes and N2O accumulative amount emissions from soil-winter wheat system and soil. O treatment significantly reduced N2O accumulative amount emissions from soil, OT treatment significantly increased N2O emission fluxes from winter-wheat field system. Experimental warming and elevated O3did not change the time variation of soil Gn and D rates compared with CK. During the entire growth period, Gn and D rates showed an inconsistent variation, while T and OT treatments addition significantly promoted Gn rates and reduced D rates. The results of the soybean growing season showed that:T, O and OT treatments did not change the seasonal variation patterns of N2O emission fluxes from soil-soybean system and soil. Compared with CK, T significantly increased N2O emission fluxes and N2O accumulative amount emissions from soil-soybean system and soil, while O、OT significantly reduced N2O emission fluxes and N2O accumulative amount. Experimental warming and elevated O3did not change the time variation of soil Gn and D rates compared with CK. During the entire growth period, T treatment significantly increased soil Gn rate, and OT also significantly increased Gn rate. Four different treatments slightly promote D rates, but there no significant difference.T significantly increased the biomass of winter wheat during the jointing-booting stage, heading-flowering stage, and filling stage, while significantly reduced the biomass in maturity. Elevated O3significantly reduced the biomass in filling stage and maturity. Experimental Warming and elevated O3significantly increased the biomass during jointing-booting stage and heading-flowering stage, while addition significantly reduced the biomass in maturity. Experimental Warming reduced the biomass of soybean in maturity, but there no significant difference was found. O and OT treatments significantly reduced soybean biomass in maturity, and the effect of OT was stronger then O treatment.During the entire growth period, T and OT treatments significantly increased nitrate reductase activities of winter wheat leaves, while O had no significant effect. T and OT treatments addition significantly increased nitrate reductase activities of soybean leaves, and O significantly increased nitrate reductase activity.