Assimilation of atmospheric carbon dioxide (CO₂) by autotrophic microbes is an integral process in the soil environment. However, the influence of disturbed and undisturbed soils on CO₂assimilation capacity remains poorly understood. In this study, we incubated four types of disturbed and undisturbed soil samples for 110 days in a closed, continuously ¹⁴Clabeled CO₂ atmosphere and measured the amount of ¹⁴Clabeled carbon (C) incorporated in the microbial biomass during this period. The allocation of ¹⁴Clabeledassimilated C in labile soil C pools such as dissolved organic C (DOC) and microbial biomass C (MBC) was analyzed over the ¹⁴Clabeling span. Significant amounts of ¹⁴C-SOC were detected in both disturbed and undisturbed soils. The assimilative rate ranged from 0.015 to 0.148 g·m^-2·d^-1 in the disturbed soils and from 0.007 to 0.050 g·m^-2·d^-1 in the undisturbed soils. A significant positive linear relationship was detected between the concentrations of ¹⁴C-SOC and ¹⁴C-MBC (R²=0.955, P<0.01). The proportions of ¹⁴C-DOC, ¹⁴C-MBC, and ¹⁴C-SOC to the total DOC, MBC, and SOC were 0.9%-4.5%, 2.2%-9.7%, and 0.09%-0.43% in the undisturbed soils, and 0.26%-1.09%, 3.6%-20%, and 2.9%-5.7% in the disturbed soils, respectively. Furthermore, the distribution and transformation of microbeassimilated C had much greater influence on the dynamics of DOC and MBC than on those of SOC. These results offer new insights into the importance of microbes in the assimilation of atmospheric CO₂ and of the potentially significant contributions made by microbial autotrophy to terrestrial C cycling.