Response of ecosystem CO(2) fluxes to grazing intensities – a five-year experiment in the Hulunber meadow steppe of China

Grazing is the primary land use in the Hulunber meadow steppe. However, the quantitative effects of grazing on ecosystem carbon dioxide (CO(2)) fluxes in this zone remain unclear. A controlled experiment was conducted from 2010 to 2014 to study the effects of six stocking rates on CO(2) flux, and the results showed that there were significant differences in CO(2) fluxes by year, treatment, and month. The effects of light and intermediate grazing remained relatively constant with grazing year, whereas the effects of heavy grazing increased substantially with grazing duration. CO(2) flux significantly decreased with increasing grazing intensity and duration, and it was significantly positively correlated with rainfall, soil moisture (SM), the carbon to nitrogen ratio (C/N ratio), soil available phosphorus (SAP), soil NH(4) (+)-N, soil NO(3) (−)N, aboveground biomass (AGB), coverage, height, and litter and negatively correlated with air temperature, total soil N (TN) and microbial biomass N (MBN). A correspondence analysis showed that the main factors influencing changes in CO(2) emissions under grazing were AGB, height, coverage, SM, NH(4) (+)-N and NO(3) (−)N. Increased rainfall and reduced grazing resulted in greater CO(2) emissions. Our study provides important information to improve our understanding of the role of livestock grazing in GHG emissions.