Forests are important contributors to the global carbon (C) cycle because they store large quantities of C in the vegetation and soil, and exchange CO₂ actively with the atmosphere through photosynthesis and respiration. Urban forests are a critical part of green infrastructure that not only maintains the health and quality of life in the cities, but also provides many ecosystem services, such as C sequestration in urban areas. In the present study, the quantity and distribution of vegetation biomass, C content and C storage were investigated in four types of forests (Masson pine forests, Chinese fir forests, Bamboo forests, and Poplar forests) in Changsha City, Hunan Province. The C sequestration capacity was also estimated for the four forest ecosystems. The results showed that the biomass of overstory vegetation was 135.390, 100.578, 64.497, and 63.381 t/hm² in masson pine, Chinese fir, bamboo and poplar forests, respectively. Stem had the highest, whereas fine root had the lowest proportion of overstory biomass among the different organs for all examined forests. The biomass was 18.374, 22.321, 1.847, and 2.602 t/hm² in understory vegetation and litter layers in masson pine, Chinese fir, bamboo, and poplar forests, respectively. On average, C content was found in the range of 0.405-0.551 gC/g in overstory vegetation with specifically ranging of 0.405-0.516, 0.458-0.509, 0.405-0.527, and 0.454-0.551gC/g in masson pine, Chinese fir, bamboo, and poplar forests, respectively. Average C content ranged between 0.421-0.518 gC/g in understory vegetation, 0.230-0.545 gC/g in litter layer, and 15.669-19.163 gC/g in the soil. The C content of soils under the four forest types decreased with increasing soil depth. The total C storage was 208.67, 176.723, 149.17 and 164.74 t/hm² in masson pine, Chinese fir, bamboo, and poplar forest ecosystems, respectively. Of which, the largest proportion of the total C storage was found in the soils that contained 134.64, 116.91, 115.99, and 126.86 t/hm² in the corresponding four forest types, respectively. The next was vegetation component that contained 33.976, 47.871, 32.632, and 66.346 t/hm² in the four studied forests. The litter layer accounted for the least percentage of the total C storage for the four examined forest types with a range of 0.39-6.16 t/hm². On average, the annual C sequestration in the four forest ecosystems was 3.969, 3.420, 6.019, and 1.759 t hm^-2 a^-1 was in masson pine, Chinese fir, bamboo, and poplar forests, respectively. The total C sequestration capacity in the four forest ecosystems (15.167 t hm^-2 a^-1) was roughly equal to 55.602 t hm^-2 a^-1 of CO₂ fixation in the study site. Our results demonstrate the significance of urban forest ecosystems in carbon sequestration to mitigate climate change. The results provide a scientific basis and reference for urban forest planning and management and an accurate estimation of C balances in urban forest ecosystems.