The Global Turnover Time Distribution of Soil Carbon Derived from a Meta-analysis of Radiocarbon Profiles

Monday, December 14, 2015 - 18:25
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Preliminary results indicated that climate and depth were primary controls of the vertical distribution of ∆14C, contributing to about 70% of the variability in our model. Vegetation and soil order exerted similar level of controls (about 15% each). The predictive model performed reasonably well with an R2 of 0.81 and RMSE (root-mean-squared error) of about 50‰ for topsoil and 100‰ for subsoil, as estimated using cross-validation. Extrapolation of the predictive model to the globe in combination with existing soil carbon information (e.g., Harmonized World Soil Database) indicated that more than half of the global total soil carbon in the top 1m had a turnover time of less than 500 years. Subsoils (30-100cm) had millennium-scale turnover times, with the majority (70%) turning over between 1000 and 5000 years. This study provides a data-constrained estimate of the global distribution of soil carbon turnover times and may help to constrain the performance of Earth system models used to evaluate future scenarios of change.