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

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 (R-s) of a semi-arid temperate grassland during two growing seasons in Inner Mongolia, northern China, and to identify the main factors that affected R-s. During the growing season, R-s for the mowing, grazing exclusion, and grazing land-use types averaged 129, 150, and 194 g Cm-2 yr(-1), respectively, in 2011 (a dry year), versus 309, 272, and 262 g Cm-2 yr(-1), respectively, in 2012 (a wet year). Root respiration (R-r) accounted for 13-55% of R-s in 2011, versus 10-62% in 2012. R-s was strongly positively correlated with soil moisture for all three land uses, but weakly correlated with soil temperature (R-2 < 0.4 in all cases). R-s was significantly positively correlated with aboveground biomass (R-2 = 0.834), soil organic matter (R-2 = 0.765), root biomass (R-2 = 0.704), lignin mass loss rate (R-2 = 0.422), and the cellulose mass loss rate (R-2 = 0.849) and significantly negatively correlated with the litter C/N (R-2 = 0.609). The temperature sensitivity (Q(10)) 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. (C) 2014 Elsevier B.V. All rights reserved.