[Effects of long-term grazing on carbon isotope composition in plants and soils of different grassland]

Grazing is a common human activity on grassland region. Long-term grazing exerts great effects on ecosystem carbon cycling. In this study, we collected leaf and soil samples from different grassland types across the growing season, separately from un-grazed (UG) and overgrazed (OG) plots. By analyzing the carbon isotope values of samples in laboratory, this study revealed the divergent Δ¹³C value (carbon isotope discriminative value) among different grassland ecosystems, as well as its influencing factors. The results showed that Δ¹³C value of soil at 0-5 cm significantly differed between UG and OG, but no difference at deeper layers (>5 cm). The grazing intensity had significant influence on the Δ¹³C value of vegetation leaves. After long-term grazing, most vegetation showed a significant increase in Δ¹³C value, especially in high altitude areas. In conclusion, grazing have significantly divergent impacts on the carbon processes under different grassland ecosystems, soil depths and altitudes. Therefore, a variety of grazing management strategies should be adopted for various grassland ecosystems.