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A potential loss of carbon associated with greater plant growth in the European Arctic

Nature Climate Change volume 2, pages 875879 (2012) | Download Citation


Rapid warming is expected to increase plant growth in the Arctic1, and result in trees gradually colonizing tundra2. Models predict that enhanced carbon (C) storage in plant biomass may help offset atmospheric CO2 increases and reduce rates of climate change2,3,4. However, in some Arctic ecosystems, high plant productivity is associated with rapid cycling and low storage of soil C (refs 1, 5, 6); thus, as plant growth increases, soil C may be lost through enhanced decomposition. Here we show that, in northern Sweden, total ecosystem C storage is greater in tundra heath (owing to greater soil C stocks) than in more productive mountain-birch forest. Furthermore, we demonstrate that in the forest, high plant activity during the middle of the growing season stimulates the decomposition of older soil organic matter. Such a response, referred to as positive priming, helps explain the low soil C storage in the forest when compared with the tundra. We suggest that, as more productive forest communities colonize tundra, the decomposition of the large C stocks in tundra soils could be stimulated. Thus, counter-intuitively, increased plant growth in the European Arctic could result in C being released to the atmosphere, accelerating climate change.

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This work was carried out within the Natural Environment Research Council (NERC) funded Arctic Biosphere Atmosphere Coupling at Multiple Scales (ABACUS; www.abacus-ipy.org) project (a contribution to International Polar Year 2007–2008) under grants NE/D005833/1 and NE/D005884/1. We are grateful for the help of the staff at the Abisko Scientific Research Station. We thank L. English for assisting with the laboratory analyses, and J. Zaragoza-Castells and A. Bennett for their helpful comments on the manuscript.

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Author notes

    • Iain P. Hartley
    •  & David W. Hopkins

    Present addresses: Geography, College of Life and Environmental Sciences, University of Exeter, Amory Building, Rennes Drive, Exeter EX4 4RJ, UK (I.P.H.); School of Life Sciences, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK (D.W.H.)


  1. Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK

    • Iain P. Hartley
    • , David W. Hopkins
    •  & Philip A. Wookey
  2. NERC Radiocarbon Facility (Environment), Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, Glasgow G75 0QF, UK

    • Mark H. Garnett
  3. James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK

    • Martin Sommerkorn
  4. Department of Plant and Animal Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK

    • Benjamin J. Fletcher
    • , Victoria L. Sloan
    •  & Gareth K. Phoenix


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P.A.W., I.P.H., D.W.H. and M.S. designed the study. Soil surveys were carried out by I.P.H., M.S. and P.A.W., and 14CO2 collection and analysis was led by M.H.G. The plant community surveys were designed and carried out by B.J.F., V.L.S. and G.K.P. All authors contributed to writing the manuscript.

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The authors declare no competing financial interests.

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Correspondence to Iain P. Hartley or David W. Hopkins.

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