Dynamics on forest carbon stock in Sichuan Province and Chongqing City
四川省及重庆地区森林植被碳储量动态

Forest in Sichuan (including Chongqing) locate in the eastern of Tibet Plateau honored by the third pole in the world. As a principal part of SW forest region, the second largest forest region in China, the forest carbon stock plays an important role in global carbon cycle, implying that it is important for forest carbon stock evaluation to understand the role of the forest in mitigating climate change. Therefore, carbon stocks in Sichuan (including Chongqing) forest at different phases were evaluated to understand the contribution of Sichuan forest to mitigate climate change, employing the methods of establishing the model of forest biomass and volume, measuring carbon content in different stands and integrating four provincial forest inventory data in Sichuan (including Chongqing). Mean carbon content of the studied forest stands was 51.09%, ranging from 46.75% to 54.89% ,and depending on the forest stands. On average, carbon content was 52.82% in the coniferous forest, which was significantly higher than that in the broadleaved forest (49.37%). Forest carbon stock in Sichuan increased 140.53 Tg C from 383.04 TgC in 1998 to 523.57 TgC in 2003 and by 2.11% annually during the study period, which was more 0.22% than that of the mean increment in China, implying that Sichuan (including Chongqing) forest is carbon sink in atmospheric carbon dioxide, and contributes to climate change mitigation. Correspondingly, average carbon density in the forest was 38.93, 38.68, 39.17 MgC/hm2, and 41.66 MgC/hm2, respectively, and showed the increasing trend during the period of four forestry inventories, implying that the potential of carbon sink in Sichuan (including Chongqing) forest was increasing. Carbon stock in mature forest showed the declining trend in the study period, which accounted for 64.15%, 63.89%, 65.33%, and 60.82% of the total in the corresponding phase, respectively, while that in young and middle-aged forest showed the opposite, showing that the study forest has a strong potential of carbon sequestration. Meanwhile, the potential of carbon sequestration in the plantation increased continuously although natural forest stored carbon more than 90% for the same stage, resulting that annual increment of carbon stock in the plantation was 7.17% in comparison with 1.83% in natural forest. The results showed that man-made forest played an important role in enhancing forest carbon sequestration in the study region. Furthermore, the results also showed that Sichuan the study forest played an important and irreplaceable role in enhancing national forest carbon sequestration due to higher carbon sequestration in the forest in comparison with national level.