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Ambient ultraviolet radiation in the Arctic reduces root biomass and alters microbial community composition but has no effects on microbial biomass

Authors

  • R. Rinnan,

    1. Department of Terrestrial Ecology, Institute of Biology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark,
    2. Department of Ecology and Environmental Science, University of Kuopio, PO Box 1627, FI-70211 Kuopio, Finland,
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  • M. M. Keinänen,

    1. National Public Health Institute, Department of Environmental Health, Laboratory of Environmental Microbiology, PO Box 95, FI-70701 Kuopio, Finland,
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  • A. Kasurinen,

    1. Department of Ecology and Environmental Science, University of Kuopio, PO Box 1627, FI-70211 Kuopio, Finland,
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  • J. Asikainen,

    1. Department of Ecology and Environmental Science, University of Kuopio, PO Box 1627, FI-70211 Kuopio, Finland,
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  • T. K. Kekki,

    1. Department of Ecology and Environmental Science, University of Kuopio, PO Box 1627, FI-70211 Kuopio, Finland,
    2. National Public Health Institute, Department of Environmental Health, Laboratory of Environmental Microbiology, PO Box 95, FI-70701 Kuopio, Finland,
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  • T. Holopainen,

    1. Department of Ecology and Environmental Science, University of Kuopio, PO Box 1627, FI-70211 Kuopio, Finland,
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  • H. Ro-Poulsen,

    1. Department of Terrestrial Ecology, Institute of Biology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark,
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  • T. N. Mikkelsen,

    1. Plant Research Department, Risø National Laboratory, DK-4000 Roskilde, Denmark
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  • A. Michelsen

    1. Department of Terrestrial Ecology, Institute of Biology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark,
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Riikka Rinnan, fax +45 35 32 23 21, e-mail: riikkar@bi.ku.dk

Abstract

We assessed the effects of ambient solar ultraviolet (UV) radiation on below-ground parameters in an arctic heath in north-eastern Greenland. We hypothesized that the current UV fluxes would reduce root biomass and mycorrhizal colonization and that these changes would lead to lower soil microbial biomass and altered microbial community composition. These hypotheses were tested on cored soil samples from a UV reduction experiment with three filter treatments (Mylar, 60% UV-B reduction; Lexan, up to 90% UV-B reduction+UV-A reduction; UV transparent Teflon, filter control) and an open control treatment in two study sites after 3 years' manipulation. Reduction of both UV-A and UV-B radiation caused over 30% increase in the root biomass of Vaccinium uliginosum, which was the dominant plant species. UV reduction had contrasting effects on ericoid mycorrhizal colonization of V. uliginosum roots in the two sites, while it had no clear effects on fungal (ergosterol) or microbial biomass (measured both with fumigation–extraction and quantitative lipid biomarker analysis) in soil. However, principal component analysis of lipid biomarkers (phospholipid and glycolipid fatty acid profiles) showed that microbial community composition was altered by UV reduction. Although the UV responses were slight considering the large dose difference between the treatments (from near-ambient to up to 90% UV-B reduction), we cannot rule out the possibility that the recovery of ozone layer would change the below-ground functioning of arctic ecosystems.

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