Grazing is one of the most important ways for managing grassland in northern China. Different studies have focused on the effects of grazing on the structure and function of ecosystems. Grazing affects the structure and function of soil via biological and physical processes, such as animal trampling, feeding, and excretion, which further affects N2O emissions. However, there is less research on greenhouse gases (GHGs) emissions by grazing intensities in semi-arid grassland ecosystems in northern China. In this study, four different grazing intensities were considered in the semi-arid grassland ecosystem of the typical agro-pastoral ecotone in northern China (Youyu, Shanxi). The influence of different grazing intensities on GHG fluxes was studied by measuring GHGs fluxes in the growing season with an opaque static chamber. The results showed that ① Grazing had no effect on CO2 and N2O fluxes during the first year of grazing treatment. ② However, grazing decreased soil water content (P<0.05), moderate grazing intensity decreased microbial biomass carbon (P<0.05), and moderate and heavy grazing intensities reduced microbial biomass nitrogen (P<0.05). ③ Significant positive correlations between CO2 flux and soil temperature and soil moisture were observed. The correlation between temperature and CO2 emissions was increased by grazing. ④ There was a significant positive correlation between soil temperature, soluble nitrogen, soil microbial biomass nitrogen, CO2 flux, and N2O flux. Our results indicated that GHG, regulated by soil microorganisms, was affected by soil temperature and moisture.
Keywords: agro-pastoral ecotone; grazing; greenhouse gas; microbial biomass; semi-arid grassland ecosystem.