Estimation of biomass, net primary production and net ecosystem production of China's forests based on the 1999–2003 National Forest Inventory

Abstract The National Forest Inventory (NFI) is an important resource for estimating the national carbon (C) balance. Based on the volume, biomass, annual biomass increment and litterfall of different forest types and the 6th NFI in China, the hyperbolic relationships between them were established and net primary production (NPP) and net ecosystem production (NEP) were estimated accordingly. The results showed that the total biomass, NPP and NEP of China's forests were 5.06 Pg C, 0.68 Pg C year−1 and 0.21 Pg C year−1, respectively. The area-weighted mean biomass, NPP and NEP were 35.43 Mg C ha−1, 4.76 Mg C ha−1 year−1 and 1.47 Mg C ha−1 year−1 and varied from 13.36 to 79.89 Mg C ha−1, from 2.13 to 9.15 Mg C ha−1 year−1 and from −0.16 to 5.80 Mg C ha−1 year−1, respectively. The carbon sequestration was composed mainly of Betula and Populus forest, subtropical evergreen broadleaved forest and subtropical mixed evergreen–deciduous broadleaved forest, whereas Pinus massoniana forest and P. tabulaeformis forest were carbon sources. This study provides a method to calculate the biomass, NPP and NEP of forest ecosystems using the NFI, and may be useful for evaluating terrestrial carbon balance at regional and global levels.