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Reduction of forest soil respiration in response to nitrogen deposition

Abstract

The use of fossil fuels and fertilizers has increased the amount of biologically reactive nitrogen in the atmosphere over the past century. As a consequence, forests in industrialized regions have experienced greater rates of nitrogen deposition in recent decades. This unintended fertilization has stimulated forest growth, but has also affected soil microbial activity, and thus the recycling of soil carbon and nutrients. A meta-analysis suggests that nitrogen deposition impedes organic matter decomposition, and thus stimulates carbon sequestration, in temperate forest soils where nitrogen is not limiting microbial growth. The concomitant reduction in soil carbon emissions is substantial, and equivalent in magnitude to the amount of carbon taken up by trees owing to nitrogen fertilization. As atmospheric nitrogen levels continue to rise, increased nitrogen deposition could spread to older, more weathered soils, as found in the tropics; however, soil carbon cycling in tropical forests cannot yet be assessed.

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Figure 1: Effect of experimental nitrogen addition on various forest carbon pools and fluxes as calculated by meta-analysis.
Figure 2: Relative effect of nitrogen addition on heterotrophic respiration and soil carbon dioxide efflux.
Figure 3: Observed annual heterotrophic respiration rates and soil carbon dioxide efflux as a function of annual biomass production (NPP) in forests exposed to elevated or background nitrogen deposition.

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Acknowledgements

This paper is dedicated to the memory of L. Misson, good friend and esteemed scientist. The authors acknowledge J. Gash for language editing. I.A.J. and R.C. acknowledge support from the UA-Research Centre of Excellence ECO Methusalem funding, the EC-FP7 project GHG Europe, and the Flemish National Science Foundation (FWO-Flanders). S.L. is funded by the ERC starting grant 242564. B.E.L. acknowledges the Office of Science (BER) US Department of Energy (award DE-FG02-04ER63911) for support of Ameriflux synthesis. J.A.S. acknowledges support from the UK Natural Environment Research Council (grant NE/E004512/1).

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I.A.J., W.D. and S.L. conceived the manuscript. S.L., W.D., J.A.S. and B.E.L. provided the data. W.D. and S.L. performed the analyses. All authors collaborated in the writing.

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Correspondence to I. A. Janssens.

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Janssens, I., Dieleman, W., Luyssaert, S. et al. Reduction of forest soil respiration in response to nitrogen deposition. Nature Geosci 3, 315–322 (2010). https://doi.org/10.1038/ngeo844

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