Conclusions
In this study, we assessed the impact of different levels of grazing intensity, as well as the associated direct and indirect effects, on ecosystem carbon exchange and soil respiration. Over the course of the growing season, we found that the desert steppe remained in a state of carbon uptake (carbon sink) under the conditions of 16 years of continuous grazing. Our study shows that alter patterns of net ecosystem exchange primarily via their negative influence on the biomass of shrubs and semi-shrubs. In addition, grazing-induced reduction belowground biomass, as well as in total plant nitrogen and soil ammonium nitrogen, can strongly influence ecosystem carbon exchange and soil respiration. When nitrogen is lost from the soil due to grazing, plants reallocate resources belowground to maintain growth and development, thus promoting photosynthesis and respiration.