Effects of Enhanced UV-B Radiation on N_2O Emission in a Soil-Winter Wheat System

摘要

An outdoor pot experiments was conducted to investigate the effects of enhanced ultraviolet-B (UV-B) radiation on nitrous oxide (N_2O) emissions from soil-winter wheat systems. The enhanced UV-B radiation treatments were simulated by 20% increase in its intensity. N_2O fluxes were measured with a static opaque chamber-gas chromatograph method. The results showed that enhanced UV-B radiation did not change the seasonal patterns of N_2O emissions. Compared to the controls, the enhanced UV-B radiation reduced N_2O fluxes by 16.4% (p=0.015) during the elongation-booting stage, while it had no significant effects on N_2O fluxes in the turning-green and heading-maturity phases. During the turning green-overall heading span, the accumulative N_2O was largely decreased by the enhanced UV-B radiation (p<0.05). From the overall heading to maturity, however, the effects of enhanced UV-B on N_2O emissions were not pronounced (p>0.10). At the elongation-booting stage, enhanced UV-B increased soluble proteins content in leaves, NO_3~--N and NO_4~+-N content in rhizosphere soil, and soil microbial biomass C (C_(mic)) and N (N_(mic); p<0.05), as well as microbial biomass C:N ratio changing from 5.0 to 6.8. Our findings suggest that the effects of enhanced UV-B radiation on N_2O emissions differed with winter wheat developmental stages. To assess the overall effects of enhanced UV-B radiation on N_2O emissions from agroecosystems, nevertheless, more field measurements deserve to be carried out in various cropping systems.