Journal Article

Impacts of warming and fertilization on nitrogen-fixing microbial communities in the Canadian High Arctic

Julie R. Deslippe, Keith N. Egger and Greg H.R. Henry

in FEMS Microbiology Ecology

Volume 53, issue 1, pages 41-50
Published in print June 2005 |
Published online January 2006 | e-ISSN: 1574-6941 | DOI:

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The impacts of simulated climate change (warming and fertilization treatments) on diazotroph community structure and activity were investigated at Alexandra Fiord, Ellesmere Island, Canada. Open Top Chambers, which increased growing season temperatures by 1–3 °C, were randomly placed in a dwarf-shrub and cushion-plant dominated mesic tundra site in 1995. In 2000 and 2001 20N:20P2O5:20K2O fertilizer was applied at a rate of 5 g m−2 year−1. Estimates of nitrogen fixation rates were made in the field by acetylene reduction assays (ARA). Higher rates of N fixation were observed 19–35 days post-fertilization but were otherwise unaffected by treatments. However, moss cover was significantly positively associated with ARA rate. NifH gene variants were amplified from bulk soil DNA and analyzed by terminal restriction fragment length polymorphism analysis. Non-metric multidimensional scaling was used to ordinate treatment plots in nifH genotype space. NifH gene communities were more strongly structured by the warming treatment late in the growing season, suggesting that an annual succession in diazotroph community composition occurs.

Keywords: Nitrogen fixation; nifH; T-RFLP; Acetylene reduction assay; Arctic; Climate change; Moss

Journal Article.  6402 words.  Illustrated.

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