Greenhouse gases contribute to increasing atmospheric temperatures, with carbon dioxide being the most important contributor. One of the most effective approaches for reducing atmospheric carbon dioxide concentrations is its sequestration in soils. This study investigated soil organic carbon (SOC) content and carbon sequestration (CS) at surface (0–15 cm) and subsurface (15–30 cm) depths under different land uses, including forest, agricultural land, and tree plantations, in the Gyan Plain, Hamadan Province, Iran. Soil samples were randomly collected from 48 locations at two depths, and various physical and chemical soil properties were analyzed. CS was calculated for both soil depths. Pearson correlation analysis at the surface depth showed significant negative correlations between SOC and clay plus silt content (r = −0.33, p < 0.01), while significant positive correlations were observed with cation exchange capacity (CEC) (r = 0.33), sand content (r = 0.32), saturation moisture content (r = 0.55), and total nitrogen (r = 0.38). At the subsurface depth, SOC showed a significant negative correlation with clay plus silt content (r = −0.45, p < 0.01), whereas saturation moisture content (r = 0.33) and sand content (r = 0.50) showed significant positive correlations with SOC. CS at both surface (r = −0.59) and subsurface (r = −0.63) depths exhibited significant negative correlations with bulk density (p < 0.01) and strong positive correlations with SOC (surface: r = 0.82; subsurface: r = 0.75; p < 0.01). Soil depth significantly affected SOC (p < 0.01) but had no significant effect on CS. Mean comparisons indicated that forest land use had the highest SOC values at both depths, while tree plantations showed the highest CS values. Agricultural land use had the lowest SOC and CS values. Among different crop types, canola and maize had the highest mean CS, whereas wheat had the lowest. Overall, conversion of forest land to agricultural land reduced SOC and CS at both depths, and crop type significantly influenced carbon storage. Therefore, implementing appropriate crop rotation strategies in agricultural systems is recommended to reduce SOC losses and enhance soil carbon sequestration.