Effects of land use on soil respiration in the temperate steppe of Inner Mongolia, China

Abstract

Land use change has greatly affected ecosystem C processes and C exchanges in grassland ecosystems. The aim of this study was to determine the effects of land use (mowing, grazing exclusion, and grazing) on soil respiration (Rs) of a semi-arid temperate grassland during two growing seasons in Inner Mongolia, northern China, and to identify the main factors that affected Rs. During the growing season, Rs for the mowing, grazing exclusion, and grazing land-use types averaged 129, 150, and 194gCm−2yr−1, respectively, in 2011 (a dry year), versus 309, 272, and 262gCm−2yr−1, respectively, in 2012 (a wet year). Root respiration (Rr) accounted for 13–55% of Rs in 2011, versus 10–62% in 2012. Rs was strongly positively correlated with soil moisture for all three land uses, but weakly correlated with soil temperature (R2<0.4 in all cases). Rs was significantly positively correlated with aboveground biomass (R2=0.834), soil organic matter (R2=0.765), root biomass (R2=0.704), lignin mass loss rate (R2=0.422), and the cellulose mass loss rate (R2=0.849) and significantly negatively correlated with the litter C/N (R2=0.609). The temperature sensitivity (Q10) exhibited large monthly changes, and ranged from 0.52 to 2.12. Rainfall plays a dominant role in soil respiration: precipitation increased soil respiration, but the response differed among the land-use types. Thus, soil water availability is a primary constraint on plant growth and ecosystem C processes. Soil temperature plays a secondary role. Litter decomposition rates and litter quality also appear to be important.