The size of the land carbon sink in China/Reply

• Published in: Nature (London) Vol. 603; no. 7901; pp. E7 - E12
• Main Authors: Wang, Yilong, Wang, Xuhui, Wang, Kai, Chevallier, Frédéric, Zhu, Dan, Lian, Jinghui, He, Yue, Tian, Hanqin, Li, Junsheng, Zhu, Jianxiao, Jeong, Sujong, Canadell, Josep G
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 17.03.2022
• Subjects: Afforestation; Atmosphere; Biomass; Carbon; Carbon dioxide; Carbon sequestration; Carbon sinks; Elevation; Estimates; Forest biomass; Forests; Greenhouse gases; Laboratories; Mountains; China
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-021-04255-y

According to the eighth (2009-2013) and ninth (2014-2018) national forest inventory data, the forest biomass carbon sink amounts to about 0.19 Pg C yr-1, including the effects of forest area expansion and afforestation. Considering a ratio of belowground biomass to aboveground biomass of about 0.21-0.23 (ref.9) and a soil carbon sink of about 0.07 Pg C yr-1 (ref.5), the resulting satellite-based estimate of the land carbon sink («0.32 Pg C yr-1) is also about one-fourth of their inversion estimate. [...]neither the ground nor satellite evidence supports the large land carbon sink they inferred. Recent estimates of these lateral fluxes3,11 (Supplementary Text 1) showed that the flux gap between top-down and bottom-up estimates should be about -0.14PgCyr-1. [...]even after this adjustment for lateral fluxes, the estimate of Wang et al.2 is still at least three times higher than the bottom-up estimates (Fig. 1). Figure 2b shows that CO2 mole fractions at Shangri-La are systematically smaller than the mean ofthe largegrid cell throughout the year, and the horizontal representativeness error at Shangri-La can be as large as -5ppm. [...]selecting a proper vertical model level to represent mountain sites is also a challenge12 when the mean elevation of the model grid can be much lower than the elevation of the station.