Observation-based global soil heterotrophic respiration indicates underestimated turnover and sequestration of soil carbon by terrestrial ecosystem models

Yue He, Jinzhi Ding* (Corresponding Author), Tsechoe Dorji, Tao Wang, Juan Li, Pete Smith

*Corresponding author for this work

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Soil heterotrophic respiration (Rh) refers to the flux of CO2 released from soil to atmosphere as a result of organic matter decomposition by soil microbes and fauna. As one of the major fluxes in the global carbon cycle, large uncertainties still exist in the estimation of global Rh, which further limits our current understanding of carbon accumulation in soils. Here, we applied a Random Forest algorithm to create a global data set of soil Rh, by linking 761 field observations with both abiotic and biotic predictors. We estimated that global Rh was 48.8 ± 0.9 Pg C year−1 for 1982–2018, which was 16% less than the ensemble mean (58.6 ± 9.9 Pg C year−1) of 16 terrestrial ecosystem models. By integrating our observational Rh with independent soil carbon stock data sets, we obtained a global mean soil carbon turnover time of 38.3 ± 11 year. Using observation-based turnover times as a constraint, we found that terrestrial ecosystem models simulated faster carbon turnovers, leading to a 30% (74 Pg C) underestimation of terrestrial ecosystem carbon accumulation for the past century, which was especially pronounced at high latitudes. This underestimation is equivalent to 45% of the total carbon emissions (164 Pg C) caused by global land-use change at the same time. Our analyses highlight the need to constrain ecosystem models using observation-based and locally adapted Rh values to obtain reliable projections of the carbon sink capacity of terrestrial ecosystems.
Original languageEnglish
Pages (from-to)5547-5559
Number of pages13
JournalGlobal Change Biology
Issue number18
Early online date14 Jun 2022
Publication statusPublished - 1 Sept 2022

Bibliographical note

This study is supported by National Natural Science Foundation of China (grant
number: 41988101), National Key R&D Program of China (2019YFA0607304), National Natural Science Foundation of China (Grant number: 42022004 and 41901085) and the Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0606).

Data Availability Statement

Soil heterotrophic respiration data from 1982 to 2018 is openly available at https://doi.org/10.5061/dryad.b2rbnzsj9. The TRENDYv9 data are available from
Stephen Sitch (s.a.sitch@exeter.ac.uk) or Pierre Friedlingstein (p.friedlingstein@exeter.ac.uk) upon reasonable request. Data source for all the environmental predictors used in the Random Forest can be found in Materials and
Methods section.


  • soil heterotrophic respiration
  • carbon turnover time
  • random forest
  • carbon cycling
  • terrestrial carbon sink
  • terrestrial ecosystem models


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