The distribution characteristics of SIC density at different stand ages from 0 to 100 cm, 100 to 200 cm, and 200 to 300 cm are shown in Fig. 3. In the comparison of SIC density of MS, 5yrs, 11yrs, 22yrs, and 46yrs, it was found that SIC density gradually increased with the increase of stand age in 0-100cm soil layer, and the difference of SIC density between MS and other stand age stages was significant, and SIC density of 46yrs was significantly higher than that of 5yrs and 11yrs. In the 100-200 cm soil layer, the SIC density with increasing stand age was similar to that of 0-100 cm. In the 200-300 cm soil layer, the change in SIC density with increasing stand age was not significant, and only the difference in inorganic carbon density between MS and other stand age stages was significant, while the difference in inorganic carbon density between other stand ages was not significant (P < 0.05). From 0 to 300 cm soil layer, the SIC density values of MS and other stand ages were 46yrs (13.57 kg m-2) > 22yrs (12.16 kg m-2) > 11yrs (11.16 kg m-2) > 5yrs (11.07 kg m-2) > MS (7.04 kg m-2) in order.