Updated estimation of forest biomass carbon pools in China, 1977-2018

China is one of the major forest countries in the world, and the accurate estimation of its forest biomass carbon (C) pool is critical for evaluating the country's C budget and ecosystem services of forests. Although several studies have estimated China's forest biomass using national forest inventory data, most of them were limited to the period of 2004-2008. In this study, we extended our estimation to the most recent period of 2014-2018. Using datasets of eight inventory periods from 1977 to 2018 and the continuous biomass expansion factor method, we estimated that the total biomass C pool and average biomass C density in Chinese forests increased from 4717 Tg C (1 Tg = 10(12) g) in the period of 1977-1981 to 7975 Tg C in the period of 2014-2018 and 38.2 Mg C ha(-1) to 45.8 Mg C ha(-1) (1 Mg = 10(6) g), respectively, with a net increase of 3258 Tg C and an annual sink of 88.0 Tg C yr(-1) . Over the most recent 10 years (20092018), the average national forest biomass C density and C sink were 44.6 Mg C ha(-1) and 154.8 Tg C yr(-1) , respectively, much larger than those of 39.6 Mg C ha(-1) and 63.3 Tg C yr(-1) in the period 1977-2008. These pronounced increases were largely attributed to afforestation practices, forest growth, and environmental changes. Our results have documented the importance of ecological restoration practices, provided an essential basis for assessing ecosystem services, and helped to achieve China's C neutrality target.