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  • Publication
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    Climatic modifiers of the response to nitrogen deposition in peat-forming Sphagnum mosses: a meta-analysis
    (2011)
    Limpens, J.
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    Granath, G.
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    Gunnarsson, U.
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    Aerts, R.
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    Bayley, S.
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    Bragazza, Luca
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    Bubier, J.
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    Buttler, Alexandre
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    van den Berg, L. J. L.
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    Francez, Andre-Jean
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    Gerdol, R.
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    Grosvernier, Philippe
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    Heijmans, M. M. P. D.
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    Hoosbeek, M. R.
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    Hotes, S.
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    Ilomets, M.
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    Leith, I.
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    Moore, T.
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    Nilsson, Mats B.
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    Nordbakken, J. F.
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    Rochefort, L.
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    Rydin, H.
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    Sheppard, L. J.
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    Thormann, M.
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    Wiedermann, M. M.
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    Williams, B. L.
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    Xu, B.
    Peatlands in the northern hemisphere have accumulated more atmospheric carbon (C) during the Holocene than any other terrestrial ecosystem, making peatlands long-term C sinks of global importance. Projected increases in nitrogen (N) deposition and temperature make future accumulation rates uncertain. Here, we assessed the impact of N deposition on peatland C sequestration potential by investigating the effects of experimental N addition on Sphagnum moss. We employed meta-regressions to the results of 107 field experiments, accounting for sampling dependence in the data. We found that high N loading (comprising N application rate, experiment duration, background N deposition) depressed Sphagnum production relative to untreated controls. The interactive effects of presence of competitive vascular plants and high tissue N concentrations indicated intensified biotic interactions and altered nutrient stochiometry as mechanisms underlying the detrimental N effects. Importantly, a higher summer temperature (mean for July) and increased annual precipitation intensified the negative effects of N. The temperature effect was comparable to an experimental application of almost 4 g N m(-2) yr(-1) for each 1 degrees C increase. Our results indicate that current rates of N deposition in a warmer environment will strongly inhibit C sequestration by Sphagnum-dominated vegetation.