Letter | Published:

14C evidence that millennial and fast-cycling soil carbon are equally sensitive to warming

Abstract

The Arctic is expected to shift from a sink to a source of atmospheric CO2 this century due to climate-induced increases in soil carbon mineralization1. The magnitude of this effect remains uncertain, largely because temperature sensitivities of organic matter decomposition2,3 and the distribution of these temperature sensitivities across soil carbon pools4 are not well understood. Here, a new analytical method with natural abundance radiocarbon was used to evaluate temperature sensitivities across soil carbon pools. With soils from Utqiaġvik (formerly Barrow), Alaska, an incubation experiment was used to evaluate soil carbon age and decomposability, disentangle the effects of temperature and substrate depletion on carbon mineralization, and compare temperature sensitivities of fast-cycling and slow-cycling carbon. Old, historically stable carbon was shown to be vulnerable to decomposition under warming. Using radiocarbon to differentiate between slow-cycling and fast-cycling carbon, temperature sensitivity was found to be invariant among pools, with a Q10 of ~2 irrespective of native decomposition rate. These findings suggest that mechanisms other than chemical recalcitrance mediate the effect of warming on soil carbon mineralization.

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Data availability

All data generated and analysed in this study are archived in the Next-Generation Ecosystem Experiments (NGEE-Arctic) data repository49 and can be accessed at https://doi.org/10.5440/1418852.

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Acknowledgements

This research was conducted through the Next-Generation Ecosystem Experiments (NGEE-Arctic) project, which is supported by the Office of Biological and Environmental Research in the US Department of Energy Office of Science.

Author information

L.J.S.V. and M.S.T. designed the soil collection and incubation procedure, L.J.S.V. collected data and designed the analysis with guidance from M.S.T., and L.J.S.V. prepared the manuscript with contributions from M.S.T.

Competing interests

The authors declare no competing interests.

Correspondence to Lydia J. S. Vaughn or Margaret S. Torn.

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Supplementary Information

Supplementary Figures 1–12 and Supplementary Tables 1–5.

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Further reading

Fig. 1: Change over time in CO2 production and \(\mathrm{\Delta}^{14}{\mathrm{C}}_{\mathrm{CO}_2}\) during sequential soil incubations.
Fig. 2: Effects of temperature and incubation time on CO2 production rate.
Fig. 3: Effects of temperature and incubation time on active-pool and passive-pool CO2 production rates.