Articles | Volume 22, issue 18
https://doi.org/10.5194/bg-22-4851-2025
https://doi.org/10.5194/bg-22-4851-2025
Research article
 | 
23 Sep 2025
Research article |  | 23 Sep 2025

Old carbon, new insights: thermal reactivity and bioavailability of saltmarsh soils

Alex Houston, Mark H. Garnett, and William E. N. Austin

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Cited articles

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Bao, R., McNichol, A. P., Hemingway, J. D., Gaylord, M. C. L., and Eglinton, T. I.: Influence of Different Acid Treatments on the Radiocarbon Content Spectrum of Sedimentary Organic Matter Determined by RPO/Accelerator Mass Spectrometry, Radiocarbon, 61, 395–413, https://doi.org/10.1017/RDC.2018.125, 2019a. 
Bao, R., Zhao, M., McNichol, A., Wu, Y., Guo, X., Haghipour, N., and Eglinton, T. I.: On the Origin of Aged Sedimentary Organic Matter Along a River-Shelf-Deep Ocean Transect, J. Geophys. Res.-Biogeo., 124, 2582–2594, https://doi.org/10.1029/2019JG005107, 2019b. 
Bianchi, T. S., Mayer, L. M., Amaral, J. H. F., Arndt, S., Galy, V., Kemp, D. B., Kuehl, S. A., Murray, N. J., and Regnier, P.: Anthropogenic impacts on mud and organic carbon cycling, Nat. Geosci., 17, 287–297, https://doi.org/10.1038/s41561-024-01405-5, 2024. 
Boström, B., Comstedt, D., and Ekblad, A.: Isotope fractionation and 13C enrichment in soil profiles during the decomposition of soil organic matter, Oecologia, 153, 89–98, https://doi.org/10.1007/s00442-007-0700-8, 2007. 
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Short summary
Saltmarshes accumulate carbon through plant growth and older material deposited during tidal inundation. We found that more energy was required to decompose old carbon than younger carbon, and the youngest carbon was also the most susceptible to decomposition in a degradation scenario. Protecting saltmarshes can help prevent carbon losses and reduce CO2 emissions. Including this vulnerable stored carbon in climate policies and carbon credit systems could make them more accurate and effective.
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