1. Max Planck Institute for Biogeochemistry, PO Box 100164, D-07701 Jena, Germany
2. QUEST, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK
3. National Center for Atmospheric Research, PO Box 3000, Boulder, Colorado 80305, USA

Correspondence to: W. Knorr¹ Correspondence and requests for materials should be addressed to W.K. (Email: wknorr@bgc-jena.mpg.de).

The sensitivity of soil carbon to warming is a major uncertainty in projections of carbon dioxide concentration and climate¹. Experimental studies overwhelmingly indicate increased soil organic carbon (SOC) decomposition^{2, 3, 4, 5, 6, 7, 8} at higher temperatures, resulting in increased carbon dioxide emissions from soils. However, recent findings have been cited as evidence against increased soil carbon emissions in a warmer world^{9, 10}. In soil warming experiments, the initially increased carbon dioxide efflux returns to pre-warming rates within one to three years^{10, 11, 12, 13, 14}, and apparent carbon pool turnover times are insensitive to temperature¹⁵. It has already been suggested that the apparent lack of temperature dependence could be an artefact due to neglecting the extreme heterogeneity of soil carbon¹⁶, but no explicit model has yet been presented that can reconcile all the above findings. Here we present a simple three-pool model that partitions SOC into components with different intrinsic turnover rates. Using this model, we show that the results of all the soil-warming experiments are compatible with long-term temperature sensitivity of SOC turnover: they can be explained by rapid depletion of labile SOC combined with the negligible response of non-labile SOC on experimental timescales. Furthermore, we present evidence that non-labile SOC is more sensitive to temperature than labile SOC, implying that the long-term positive feedback of soil decomposition in a warming world may be even stronger than predicted by global models^{1, 17, 18, 19, 20}.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.