Divergent responses of ecosystem respiration components to livestock exclusion on the Qinghai Tibetan Plateau

Grazing exclusion (GE) is an effective method for protecting degraded grasslands, and it can profoundly affect ecosystem carbon (C) cycles. Ecosystem respiration (ER), which includes both autotrophic and heterotrophic respiration (HR), accounts for the largest land-to-atmosphere C fluxes. How ER responds to GE is still unclear, however, and to investigate this, a controlled GE experiment was conducted at a meadow grassland near Qinghai Lake, China. Animal exclusion enhanced ER and aboveground plant respiration (R_agb) by 10.5% and 40.1%, respectively, but it suppressed soil respiration by 12.4% and HR by 17.6%. Positive responses of ER and R_agb were linked to increased aboveground biomass, particularly graminoids biomass. Negative responses of soil respiration and HR were associated with GE-induced changes in microbial biomass C and nitrogen. These results show that grassland responded in complex ways to GE and that ER and its components were regulated by both abiotic and biotic factors. Moreover, the divergent responses of respiration components have important implications for models of terrestrial C cycles and climate under enhanced human activities and changes in land use.