Abstract: Based on the measurements in the enclosure and uncontrolled grazing plots in the typical steppe of Xilinguole, Inner Mongolia, this paper studied the soil carbon storage and carbon sequestration in the grasslands dominated by Leymus chinensis, Stipa grandis, and Stipa krylovii, respectively, and estimated the regional scale soil carbon sequestration potential in the heavily degraded grassland after restoration. At local scale, the annual soil carbon sequestration in the three grasslands all decreased with increasing year of enclosure. The soil organic carbon storage was significantly higher in the grasslands dominated by L. chinensis and Stipa grandis than in that dominated by Stipa krylovii, but the latter had much higher soil carbon sequestration potential, because of the greater loss of soil organic carbon during the degradation process due to overgrazing. At regional scale, the soil carbon sequestration potential at the depth of 0-20 cm varied from -0.03×10⁴  to 3.71×10⁴ kg C·a^-1, and the total carbon sequestration potential was 12.1×10⁸ kg C·a^-1. Uncertainty analysis indicated that soil gravel content had less effect on the estimated carbon sequestration potential, but the estimation errors resulted from the spatial interpolation of climate data could be about ±4.7×10⁹ kg C·a^-1. In the future, if the growth season precipitation in this region had an average variation of -3.2 mm·(10 a)^-1, the soil carbon sequestration potential would be decreased by 1.07×10⁸  kg C·(10 a)^-1.

Key words: Inner Mongolia typical steppe, grassland degradation, grassland restoration, carbon sequestration potential, scaling, uncertainty analysis