Biomass carbon pools of Cunninghamia lanceolata (Lamb.) Hook. forests in subtropical China: Characteristics and potential

Chinese fir (Cunninghamia lanceolata ( Lamb.) Hook.) is one of the most important indigenous tree species in China. Owing to their rapid growth, good timber quality and short rotation time, increasing numbers of plantations are being established with successive rotations. Numerous competing hypotheses have been described to explain the decline in yield that occurs with successive rotations of the plantations. In addition, there are some uncertainties regarding the changes and characteristics of biomass carbon pools in Chinese fir forests in subtropical China, and information is lacking regarding how to improve carbon sequestration by this biomass sink. The total biomass carbon stock of the Chinese fir forest in China increased from 91.57 Tg C in 1977-1981 to 238.50 Tg C in 2004-2008, accounting for 2.48-4.32% of the national forest biomass carbon in the corresponding period. Due to the decreased yield during successive rotation for Chinese fir plantations before the 1990s, the biomass carbon stock of Chinese fir forests decreased in several regions in China during the 1980s and 1990s, and increased in the 2000s when several silvicultural measures were implemented to improving the quality of Chinese fir plantations. When compared with the age-based volume to biomass (V-B) method of determining biomass carbon stock in Chinese fir forests in Jiangxi Province, the site specific-based and the mixed forests-based scenarios would both help offset CO2 emissions by sequestrating more CO2 from the atmosphere.