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Old soil carbon is more temperature sensitive than the young in an agricultural field |
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| Authors: | Pekka Vanhala Kristiina Karhu Eloni Sonninen Hannu Fritze |
| Institution: | a Finnish Environment Institute, P.O. Box 140, FIN-00251 Helsinki, Finland b Dating Laboratory, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki, Finland c Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland |
| Abstract: | Changes in the carbon stock of soil in response to climate change would significantly affect the atmospheric carbon dioxide concentration and consequently climate. The isotopes of carbon provide a means to study the temperature sensitivities of different soil carbon fractions. Where C3 vegetation has changed for C4, soil organic matter (SOM) from the different origins have different 13C/12C ratios. Relying on this feature, we took soil samples from a control field and a field where ordinary grain (C3) vegetation was replaced by maize (C4), 5 years ago. We measured the respiration rate and the 13C/12C ratio of the CO2 produced by the samples at different temperatures. Based on these measurements, we quantified that Q10 was 3.4-3.6 for the total CO2 production while it was 2.4-2.9 at 20 °C for the maize-derived young carbon and 3.6 for the older C3-derived carbon. Our results suggest that climatic warming will accelerate especially the decomposition of the large pool of old soil carbon in these fields. |
| Keywords: | Carbon dioxide Mineralization Temperature sensitivity Carbon isotopes |
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