Terrestrial Net Ecosystem Productivity in China during 1900–2100

Terrestrial ecosystems are a critical carbon dioxide (CO2) sink for achieving carbon (C) neutrality before 2060 in China. Here, we used the Coupled Model Intercomparison Project phase 6 (CMIP6) model outputs to quantify the spatiotemporal patterns of net ecosystem productivity (NEP) and its major environmental controls, as well as the dominant C pools for NEP during 1900–2100. We found that (a) according to CMIP6 NEP spatiotemporal characteristics, terrestrial ecosystems in China sequestered 0.310 ± 0.058 Pg C·year–1 during 1980–2014 and will act as a strong C sink [from 0.515 ± 0.075 Pg C·year–1 under Shared Socioeconomic Pathway 126 (SSP126) to 0.631 ± 0.089 Pg C·year–1 under SSP585] in the future (2015–2100). Pronounced turning points were found for the temporal trends of NEP during the historical (1984) and under 4 future emissions scenarios (2057 for SSP126, 2053 for SSP245, 2038 for SSP370, and 2044 for SSP585). (b) The positive effect of temperature on NEP appears to weaken after each turning point of future scenarios. (c) The enlarged vegetation C pool size dominates the growing terrestrial ecosystem C storage. The CMIP6 projection shows that the total C storage in Chinese terrestrial ecosystems increases continuously and peaks in the 2040s to 2050s under each scenario. Future afforestation in the northeast, southeast, and southwestern regions, as well as soil C pool management in the northwest and middle north regions, will greatly contribute to achieving C neutrality in China, particularly under low emission scenario (SSP126).