Grazing effects on ecosystem CO(2) fluxes differ among temperate steppe types in Eurasia

Grassland ecosystems play a critical role in regulating CO(2) fluxes into and out of the Earth’s surface. Whereas previous studies have often addressed single fluxes of CO(2) separately, few have addressed the relation among and controls of multiple CO(2) sub-fluxes simultaneously. In this study, we examined the relation among and controls of individual CO(2) fluxes (i.e., GEP, NEP, SR, ER, CR) in three contrasting temperate steppes of north China, as affected by livestock grazing. Our findings show that climatic controls of the seasonal patterns in CO(2) fluxes were both individual flux- and steppe type-specific, with significant grazing impacts observed for canopy respiration only. In contrast, climatic controls of the annual patterns were only individual flux-specific, with minor grazing impacts on the individual fluxes. Grazing significantly reduced the mean annual soil respiration rate in the typical and desert steppes, but significantly enhanced both soil and canopy respiration in the meadow steppe. Our study suggests that a reassessment of the role of livestock grazing in regulating GHG exchanges is imperative in future studies.