Effects of grazing exclusion on CO2 fluxes in a steppe grassland on the Loess Plateau (China)

Understanding how grazing exclusion affects carbon exchange by the plant and soil features is essential for clarifying the contribution of grassland management to the carbon budget. This paper studied effects of grazing exclusion on soil respiration, ecosystem respiration, net ecosystem carbon exchange, plant and soil characterizes for two growing-seasons (2012 and 2013) in a steppe grassland on the Loess Plateau, China. Grazing exclusion markedly increased soil respiration, ecosystem respiration and net ecosystem exchange about 0.36, 0.65 and −0.10 g C m−2 d−1, respectively. Grazing exclusion enhanced aboveground biomass, belowground biomass and cover, and which were positive correlated with CO2 flux. Soil water content, rather than soil temperature, was the major environmental factor controlling soil respiration and ecosystem respiration by partial least-squares regression. The ratios of soil respiration, ecosystem respiration and net ecosystem exchange to atmospheric CO2 assimilated by photosynthesis at fenced grassland were similarly with them at grazed grassland. Results suggested that grazing exclusion was a positive management practice to help maintain or increase carbon stocks in a steppe grassland on the Loess Plateau.