• UV-B;
  • warming;
  • Peltigera;
  • nitrogen fixation;
  • depsides;
  • soralia;
  • the Arctic


  • Although the most pronounced effects of stratospheric ozone depletion and climate warming probably will occur in polar regions, arctic lichens have not been much studied in relation to climate change.
  • Samples of two arctic cyanolichens of the genus Peltigera, exposed in situ to ambient and enhanced UV-B radiation and ambient and increased temperatures, were collected in 2001, 5 yr after the establishment of the experimental set-up. Thallus dimensions and size, coverage of soralia, nitrogen fixation activity and levels of UV-C-absorbing substances were measured.
  • Warming had pronounced positive effects on the tridepsides methyl gyrophorate and gyrophoric acid, and unidentified trace substances. However, the combination of enhanced UV-B and increased temperatures did not lead to higher than control levels. Warming reduced coverage of soralia. There were no significant treatment effects on thallus size, dimensions and nitrogen fixation activity.
  • UV-B radiation did not to have any adverse effects. The accumulation of tridepsides with warming may be related to increased activity of pathogenic microorganisms or insect herbivores.