Effects of grazing management on soil respiration in a temperate typical grassland in Inner Mongolia, China

Background/Question/Methods   Grassland soil CO₂flux to the atmosphere is a significant component of the global C cycle, making a large contribution to global climate change and the C cycle. Grazing changes the carbon cycle of plant and microorganism metabolism, but available data are insufficient to assess the influence of grazing on carbon release. Current evidence suggests no clear relationships between grazing and the carbon budget in grassland ecosystems. In our study, we measured Soil respiration(Rs), soil temperature, soil water in three grazing management types from December 2014 to September 2015, and aboveground biomass, root biomass, soil total phosphorus (TP), soil total nitrogen(TN), soil microbial biomass C (MBC) and soil dissolved organic C (DOC) with three grazing management types from May to September in 2015. The objectives of this study were to address: (1) the characteristics of Rs and environmental variables (i.e., soil temperature, soil water content) in one year; (2) the effect of grazing management types on biotic and abiotic factors in the growing season.

Results/Conclusions   The results showed that mean Rs varied significantly among different grazing management types. Mean Rs rates in the growing season (From May to September) were 1.32±0.12, 1.81±0.14 and 1.41±0.07μmol·m^-2·s^-1 for grazed site, rest-grazed site and fenced site. The difference in Rs among different grazing management may result from the changes in soil temperature, soil water content and potential substrate availability (DOC and root biomass).The soil temperature and soil water content significantly influenced Rs, and DOC and root biomass could explain the difference in Rs among different grazing management.The Q₁₀ values of rest-grazed and grazed site were greater than that of fenced site in a large part of the observation time. The main reason may be the higher Q₁₀ value of Rr by root biomass promotion in grazed site. The increasing rainfall in September could be result in the largest Q₁₀ value of fenced site. The results suggest that the three grazing management types induced different impacts on the grassland; the fenced site improved the soil microbial diversity and increased the soil TN and TP.