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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 (2009–2018), 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. [ABSTRACT FROM AUTHOR]

By integrating the reflectance of 7 spectral bands of the MODerate-resolution Imaging Spectroradiaometer (MODIS) and forest inventory data with an empirical statistical model, we mapped the spatial distribution of total forest biomass carbon density (BCD) at 1 km resolution in China during the past decade. The empirical statistical model can explain 75% of the variation in BCD across 29 provinces in China ( R 2 = 0.75, P < 0.001), with a root mean square error of 9.3 Mg C ha −1 . The total forest biomass carbon storage was estimated as 6.4 ± 0.6 Pg C, with an average BCD of 42.6 ± 3.9 Mg C ha −1 during the period of 2001–2005, which is close to the estimates solely by forest inventory data. During the 2000s, the forests in China sequestered carbon by 80 ± 103 Tg C yr −1 . Our estimation is close to an independent forest biomass estimation (76 ± 10 Tg C yr −1 ) derived from passive microwave satellites (Liu et al., 2015). Most of the forest biomass carbon sink was attributed to the growth of low- and medium-biomass forests in eastern, central, and southern China. The large area of currently low-biomass forests will retain as a large potential biomass C sink in the next few decades. This implicates that low-biomass forests (most of these forests are planted forests) need well management such as selected wood harvest to keep large forest biomass carbon sinks in China. Plans of sustainable afforestation and forests protection projects by Chinese government could also enhance the forest biomass carbon sinks in the future. Nitrogen deposition in China significantly correlates with forest biomass C sinks across 2392 0.5° × 0.5° grid cells ( R = 0.54, P < 0.001), which indicate the positive impacts of nitrogen deposition on China’s forest biomass carbon sinks. Our results suggest that China forests can continue to act as a large carbon sinks in the near future because of the contributions of management of low- and medium-biomass forests, afforestation and nitrogen deposition. [ABSTRACT FROM AUTHOR]

Abstract: Several studies have reported different estimates for forest biomass carbon (C) stocks in China. The discrepancy among these estimates may be largely attributed to the methods used. In this study, we used three methods [mean biomass density method (MBM), mean ratio method (MRM), and continuous biomass expansion factor (BEF) method (abbreviated as CBM)] applied to forest inventory data to estimate China''s forest biomass C stocks and their changes from 1984 to 2003. The three methods generated various estimates of the biomass C stocks: the lowest (4.0–5.9PgC) from CBM and the highest (5.7–7.7PgC) from MBM, with an intermediate estimate (4.2–6.2PgC) from MRM. Forest age class is a major factor responsible for these method-induced differences. MBM overestimates biomass for young-aged forests, but underestimates biomass for old-aged forests; while the reverse is true for MRM. Further, the three methods resulted in different estimates of biomass C stocks for different forest types. For temperate/subtropical mixed forests, MBM generated a 92% higher estimate than CBM and MRM generated a 14% lower than CBM. The degree of the overestimates is closely related with the proportion of young-aged forest within total area of each forest type. [Copyright &y& Elsevier]

China's forests are characterized by young age, low carbon (C) density and a large plantation area, implying a high potential for increasing C sinks in the future. Using data of provincial forest area and biomass C density from China's forest inventories between 1994 and 2008 and the planned forest coverage of the country by 2050, we developed a stage-classified matrix model to predict biomass C stocks of China's forests from 2005 to 2050. The results showed that total forest biomass C stock would increase from 6.43 Pg C (1 Pg = 1015 g) in 2005 to 9.97 Pg C (95% confidence interval: 8.98 ~ 11.07 Pg C) in 2050, with an overall net C gain of 78.8 Tg C yr−1 (56.7 ~ 103.3 Tg C yr−1; 1 Tg = 1012 g). Our findings suggest that China's forests will be a large and persistent biomass C sink through 2050. [ABSTRACT FROM AUTHOR]