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

Abstract

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.