Abstract
The sensitivity of soil organic carbon (SOC) to changing environmental conditions represents a critical uncertainty in coupled carbon cycle–climate models1. Much of this uncertainty arises from our limited understanding of the extent to which root–microbe interactions induce SOC losses (through accelerated decomposition or ‘priming’2) or indirectly promote SOC gains (via ‘protection’ through interactions with mineral particles3,4). We developed a new SOC model to examine priming and protection responses to rising atmospheric CO2. The model captured disparate SOC responses at two temperate free-air CO2 enrichment (FACE) experiments. We show that stabilization of ‘new’ carbon in protected SOC pools may equal or exceed microbial priming of ‘old’ SOC in ecosystems with readily decomposable litter and high clay content (for example, Oak Ridge5). In contrast, carbon losses induced through priming dominate the net SOC response in ecosystems with more resistant litters and lower clay content (for example, Duke6). The SOC model was fully integrated into a global terrestrial carbon cycle model to run global simulations of elevated CO2 effects. Although protected carbon provides an important constraint on priming effects, priming nonetheless reduced SOC storage in the majority of terrestrial areas, partially counterbalancing SOC gains from enhanced ecosystem productivity.
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Acknowledgements
Thanks to E. Brzostek and M. Midgley for helpful comments on the manuscript and to S. Malyshev for providing the high-frequency GFDL ESM forcing. B.N.S., E.S. and S.W.P. acknowledge support in parts from the NOAA (US Department of Commerce) grant NA08OAR4320752, the USDA grant 2011-67003-30373 and the Carbon Mitigation Initiative at Princeton University, sponsored by BP. The statements, findings and conclusions are those of the authors and do not necessarily reflect the views of the NOAA, the US Department of Commerce, the US Department of Agriculture, or BP.
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B.N.S. developed the model, designed and conducted experiments, analysed the data, and wrote the paper. E.S. and S.W.P. contributed to model development and experimental design and helped write the paper. R.P.P. and A.C.O. contributed data and expertise for set-up and interpretation of site-level simulations, and helped write the paper.
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Sulman, B., Phillips, R., Oishi, A. et al. Microbe-driven turnover offsets mineral-mediated storage of soil carbon under elevated CO2. Nature Clim Change 4, 1099–1102 (2014). https://doi.org/10.1038/nclimate2436
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DOI: https://doi.org/10.1038/nclimate2436
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