Empirical estimates of regional carbon budgets imply reduced global soil heterotrophic respiration

Ciais, P., Yao, Y., Gasser, T. ORCID: https://orcid.org/0000-0003-4882-2647, Baccini, A., Wang, Y., Lauerwald, R., Peng, S., Bastos, A., Li, W., Raymond, P.A., Canadell, J., Peters, G., Andres, R., Chang, J., Yue, C., Dolman, A.J., Haverd, V., Hartmann, J., Laruelle, G., Konings, A.G., et al. (2021). Empirical estimates of regional carbon budgets imply reduced global soil heterotrophic respiration. National Science Review nwaa145. 10.1093/nsr/nwaa145.

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Abstract

Resolving regional carbon budgets is critical for informing land-based mitigation policy. For nine regions covering nearly the whole globe, we collected inventory estimates of carbon-stock changes complemented by satellite estimates of biomass changes where inventory data are missing. The net land–atmospheric carbon exchange (NEE) was calculated by taking the sum of the carbon-stock change and lateral carbon fluxes from crop and wood trade, and riverine-carbon export to the ocean. Summing up NEE from all regions, we obtained a global ‘bottom-up’ NEE for net land anthropogenic CO2 uptake of –2.2 ± 0.6 PgC yr−1 consistent with the independent top-down NEE from the global atmospheric carbon budget during 2000–09. This estimate is so far the most comprehensive global bottom-up carbon budget accounting, which set up an important milestone for global carbon-cycle studies. By decomposing NEE into component fluxes, we found that global soil heterotrophic respiration amounts to a source of CO2 of 39 PgC yr−1 with an interquartile of 33–46 PgC yr−1—a much smaller portion of net primary productivity than previously reported.

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