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The Nitrogen Fixation Potential of Arctic Cryptogram Species Is Influenced by Enhanced UV-B Radiation

Bjørn Solheim, Ulf Johanson, Terry V. Callaghan, John A. Lee, Dylan Gwynn-Jones and Lars O. Björn
Oecologia
Vol. 133, No. 1 (Sep., 2002), pp. 90-93
Published by: Springer in cooperation with International Association for Ecology
Stable URL: http://www.jstor.org/stable/4223393
Page Count: 4
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The Nitrogen Fixation Potential of Arctic Cryptogram Species Is Influenced by Enhanced UV-B Radiation
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Abstract

Effects of enhanced UV-B (representing a 15% ozone depletion) on cyanobacterial nitrogen fixation were measured at a high arctic site (Adventdalen, 79°N, Svalbard) and a subarctic site (Abisko, 68°N, Sweden). Nitrogen fixation potential (acetylene reduction) by cyanobacteria associated with the moss Sanionia uncinata in vegetation exposed to experimentally enhanced levels of UV-B for 3 and 4 years in the high arctic in Adventdalen was reduced by 50% compared to controls after 3 years. No reduction in nitrogen fixation potential was observed in cyanobacteria associated with the moss Hylocomium splendens when previously exposed to enhanced UV-B in Abisko for a 7-year period. However, in the same experiment a 50% increase in summer precipitation stimulated nitrogen fixation potential by up to 6-fold above the natural precipitation treatments both in cyanobacteria associated with vegetation exposed to natural and enhanced UV-B radiation. In contrast to the lack of UV effect on moss-associated nitrogen fixation at the subarctic site, nitrogen fixation potential by the dominant lichen species Peltigera aphthosa was reduced by 50% when measured after 8 years exposure to elevated UV-B treatment. Evidence from these studies highlights the importance of UV-B radiation for cyanobacterial nitrogen fixation in the Arctic and future impact on nitrogen availability in such plant communities.

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