Soil respiration patterns for four major land-use types of the agro-pastoral region of northern China

Abstract

Land-use types and management practices are critical factors that affect soil CO2 efflux (Rs). In the agro-pastoral area of northern China, land-use types have changed considerably during the last 60 years due to changes in the social-economic status of the human population and associated changes in land-use needs. Only a few studies have examined Rs in this region of China, and these studies have mainly focused on grazing intensity effects on Rs rather than comparisons among land-use types. The aim of this study was to evaluate annual variation of Rs for the dominant land-use types in the agro-pastoral region of northern China, including ungrazed grassland (UG), moderately grazed grassland (MG), perennial pasture (PP), and cropland (CL). Measurements of Rs were obtained throughout the year for these four land-use types using a mobile greenhouse gas analyzer. Values of Rs from the four land-use types for the growing season, non-growing season, and across the entire year were in the order PP>CL>UG>MG. Annual values of Rs in PP and CL were 1.6- and 1.1-fold greater, respectively, than that for UG, while Rs in MG was 94% of UG. Daily mean soil temperature (Ts) was the main factor that controlled Rs and explained 52–71% of the variability in daily Rs. Monthly mean temperature and precipitation explained 67–87% of the variability in monthly cumulative Rs. Annual Rs for all land-use types averaged 1.9kgCm−2yr−1 (range: 1.6–2.5) with about 94% of annual Rs occurring during the growing season. No pulses of Rs were observed during the autumn and spring freeze-thaw period, probably because of the large snow accumulation, which minimized Rs during these two periods. These results showed that land-use types exhibit different Rs that were associated with differences in temperature and precipitation. Results also suggest that conversion of UG or MG to CL and PP will likely increase Rs.