Microbial Ecology

, Volume 69, Issue 4, pp 778–787

Across-Habitat Comparison of Diazotroph Activity in the Subarctic

  • Kathrin Rousk
  • Pernille L. Sorensen
  • Signe Lett
  • Anders Michelsen
Plant Microbe Interactions

DOI: 10.1007/s00248-014-0534-y

Cite this article as:
Rousk, K., Sorensen, P.L., Lett, S. et al. Microb Ecol (2015) 69: 778. doi:10.1007/s00248-014-0534-y

Abstract

Nitrogen (N) fixation by N2-fixing bacteria (diazotrophs) is the primary N input to pristine ecosystems like boreal forests and subarctic and arctic tundra. However, the contribution by the various diazotrophs to habitat N2 fixation remains unclear. We present results from in situ assessments of N2 fixation of five diazotroph associations (with a legume, lichen, feather moss, Sphagnum moss and free-living) incorporating the ground cover of the associations in five typical habitats in the subarctic (wet and dry heath, polygon-heath, birch forest, mire). Further, we assessed the importance of soil and air temperature, as well as moisture conditions for N2 fixation. Across the growing season, the legume had the highest total as well as the highest fraction of N2 fixation rates at habitat level in the heaths (>85 % of habitat N2 fixation), whereas the free-living diazotrophs had the highest N2 fixation rates in the polygon heath (56 %), the lichen in the birch forest (87 %) and Sphagnum in the mire (100 %). The feather moss did not contribute more than 15 % to habitat N2 fixation in any of the habitats despite its high ground cover. Moisture content seemed to be a major driver of N2 fixation in the lichen, feather moss and free-living diazotrophs. Our results show that the range of N2 fixers found in pristine habitats contribute differently to habitat N2 fixation and that ground cover of the associates does not necessarily mirror contribution.

Keywords

Boreal forest Cyanobacteria Heterotrophs Methanotrophs N deposition Nitrogen fixation Subarctic tundra Symbiosis 

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Kathrin Rousk
    • 1
    • 2
  • Pernille L. Sorensen
    • 1
  • Signe Lett
    • 3
  • Anders Michelsen
    • 1
    • 2
  1. 1.Department of Biology, Terrestrial Ecology SectionUniversity of CopenhagenCopenhagenDenmark
  2. 2.Center for Permafrost (CENPERM)University of CopenhagenCopenhagenDenmark
  3. 3.Climate Impacts Research Centre, Department of Ecology and Environmental ScienceUmeå UniversityAbiskoSweden

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