- 1Imperial College London, Space, Plasma, Climate Physics, Physics, London, United Kingdom of Great Britain – England, Scotland, Wales (asb219@ic.ac.uk)
- 2ETH Zurich, Geologisches Institut, Sonneggstrasse 5, 8092 Zürich, Switzerland
- 3Eidg. Forschungsanstalt WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
Soil organic carbon (SOC) is the largest terrestrial reservoir in the active carbon cycle, and it is predicted to be a crucial component of the terrestrial carbon sink in the present day and in future climate scenarios. However, commonly used SOC models have been shown to inadequately represent SOC turnover, as evidenced by their consistent overestimation of the radiocarbon (14C) content in forest soils. This implies that models have too fast turnover rates and do not accurately capture the persistence of carbon in the different soil pools. To reconcile observational data and modeling frameworks, we conduct a detailed 14C-based study of the SOC dynamics across climatic and environmental gradients in 54 forest sites in Switzerland. At each site, we gather 14C data for the organic layers and five chemical and density fractions in the mineral soil. Calibrating a novel SOC model with these layer- and fraction-specific 14C data reveals an improved representation of turnover times and environmental dependencies, contrasting with existing models. In particular, we find that, by ignoring organic carbon respiration in the organic layers, most existing soil models have to effectively increase the turnover rates of SOC to compensate for the strongly overestimated carbon inputs into the mineral soil. Our results have the potential to significantly improve the representation of SOC in models, particularly under climate and environmental change.
How to cite: Brunmayr, A., Moreno Duborgel, M., Minich, L., Mittelbach, B., Eglinton, T., Hagedorn, F., and Graven, H.: Omission of organic layers in soil organic carbon models results in overestimation of carbon turnover rates: a 14C study of temperate and alpine forest soils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15428, https://doi.org/10.5194/egusphere-egu25-15428, 2025.