Abstract:Global warming and enhanced ultraviolet radiation on the earth′ surface are of the two most concerns in the global change. These two environmental problems are primarily caused by increasing of greenhouse gas concentration in atmosphere and exhaustion of stratospheric ozone, respectively. It is well documented that enhanced ultraviolet radiation has an effect on crop growth, which may also have impacts on greenhouse gases emissions from agroecosystem. To investigate the impacts of enhanced UV-B radiation on nitrous oxide (N2O) emissions from soil-soybean systems, field and outdoor pot experiments were carried out during two growing seasons under the condition of simulating 20% enhancement of UV-B. Nitrous oxide emissions were measured by static chamber-gas chromatograph method. Results indicated that the enhanced UV-B radiation did not change the seasonal pattern of N2O emission from soil-soybean system, while it declined the flux and cumulative amount of N2O during pod-maturity stage. A biomass clipping method was employed to distinguish the influence of enhanced UV-B on N2O flux from soybean plant and soil in different developmental stages. Both N2O emissions from soils during the branching-flowering stage and those from soybean plants during the pod-filling stage were significantly decreased by the enhanced UV-B. Agroecosystem N2O emissions declined by enhanced UV-B radiation were primarily due to the decrease in N2O emissions from soybean plants rather than from soil. In contrast with the control, enhanced UV-B radiation remarkably decreased soybean biomass, changed the process of the nitrogen metabolism of soybean plant, and significantly raised the soil available nitrogen and soil microbial biomass ratio of C/N. The results of this study suggested that enhanced UV-B radiation could reduce N2O emissions from agricultural ecosystems.