Studies on the variation of CO2 fluxes and its characterization with soil temperature, moisture and dissolved organic carbon under different sulfur levels from alpine grassland in the Tibetan Plateau

Aim : The effect of sulfur deposition on the carbon dynamics of alpine grasslands has received little attention The present study was carried out to determine the influence of sulfur addition on temporal variation of CO2 fluxes and characterize the relationships between CO2 fluxes and soil temperature, moisture and dissolved organic carbon from alpine grassland in the Tibetan Plateau. Methodology : Based on a multi-level S (0, 2 and 6 g S m(-2) yr(-1)) addition experiment, soil CO2 fluxes were monitored by static chamber and gas chromatograph technique within Tibetan alpine grassland during the growing seasons in 2013 and 2014. Soil temperature, moisture, dissolved organic carbon, microbial carbon and nitrogen and enzyme activities were measured to examine the key driving factors of soil CO2 fluxes. Results : No significant differences in CO2 fluxes between treatments were observed during almost all the sampling periods, but sulfur deposition increased mean soil dissolved organic carbon concentrations. Sulfur deposition tended to inhibit soil microbial carbon and nitrogen and enzyme activities.Regardless of sulfur treatment, soil temperature was the primary control on seasonal variation of CO2 fluxes in both 2013 and 2014, but these fluxes were not limited by soil moisture in 2013. Interpretation : The result indicated that CO2 fluxes from Tibetan alpine grasslands resulted from mineralization of soil dissolved organic carbon and the potential increasing atmospheric sulfur deposition could have limited effects on CO2 emission from the alpine grasslands. [GRAPHICS] .