Aims The temperature sensitivity and priming effect of soil respiration, or soil carbon (C) mineralization, have been important topics for global change ecology in recent decades. They can provide new evidence on the controlling mechanisms of soil respiration in future climate change. Our objective was to investigate the effect of grazing enclosure on the priming effect and temperature sensitivity of soil C mineralization in grasslands.
Methods We selected three Leymus chinensis grasslands subjected to different grazing-exclusion durations in Inner Mongolia, i.e., grazing-free grassland (FG0), 11-year fenced grassland (FG11), and 31-year fenced grassland (FG31). We incubated the soils at 0, 5, 10, 15, 20, 25 °C, respectively.
Important findings Enclosure duration, glucose addition, incubation temperatures and incubation time all had significant impact on soil C mineralization rate, and there were significant interaction effects among these factors (p < 0.000 1). The cumulative emission of soil C mineralization was significantly higher in FG0 than in FG11 and FG31, and showed the same trend after glucose addition. Long-term enclosure decreased the priming effect of soil C mineralization in L. chinensis grasslands. After glucose addition, the priming effect of soil C mineralization was about 2.28–9.01 times and increased with increasing temperature in 7-day incubation. In 56-day incubation, the priming effect was in the range of 2.21–5.10, with the highest value at 10 or 15 °C. The temperature sensitivity of soil C mineralization can be well depicted by classical exponential equations, and the temperature sensitivity index (Q10) of soil C mineralization was higher in FG0 than in FG11 and FG31. Glucose addition significantly increased Q10, which indicated that soil microbial respiration under glucose addition was more affected by temperature. In conclusion, long-term enclosure reduced soil C mineralization rates, temperature sensitivity and priming effect in Inner Mongolian grasslands, which indicated that these long-term fenced grasslands have the capacity to further sequester CO2 from the atmosphere.