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Soil organic carbon mineralization potential in four different sandy habitats (shifting, semi-fixed, fixed sand dune, and interdunal lowland) and the effects of litter addition from shrubs and annual plants on soil microbial respiration were measured using a laboratory soil incubation experiment. Soil samples were collected from beneath and outside the canopies of shrubs in all habitats. Soils were incubated for 33 days with and without litter addition. It was concluded that the differences in C mineralization of soils among habitats correlated with the vegetation cover, litter accumulation, and soil structure, organic C, and N contents. Very poor organic C and N as well as very weak microbial respiration were found in soils of the shifting sand dune, suggesting that sandy desertification strongly depleted both bulk of soil organic C and soil labile C pool. Caragana microphylla litter amended soils and annual plant litter amended soils had the greatest and the lowest microbial respiration, respectively, which might in part be attributed to the N contents and C/N ratios in litters. Shrubs accumulated more organic material and created fertile islands with larger organic C and nutrients and microbial activity under their canopies, and therefore, significantly contributed to C sequestration.