Abstracts
SEARCH Open Science Meeting
October 27, 2003
Seattle, Washington, USA
The Effect of Temperature, Water Content, and Light Intensity and Quality on Nitrogen Fixation in High Arctic Tundra Vegetation
Matthias Zielke1, Rolf A. Olsen2, Bjørn Solheim3
1Department of Biology, University of Tromsø, Tromsø, 9037, Norway, Phone 47-77-664-6607, Fax 47-77-664-6333, matthias.zielke@ib.uit.no
2The University Centre in Svalbard, P.O. box 156, Longyearbyen, 9171, Norway, Phone 477-902-3300, Fax 477-902-3301
3Department of Biology, University of Tromsø, Tromsø, Norway
Terrestrial primary production in the High Arctic is often limited by low nitrogen content of the soil. Due to general low precipitation in these regions, deposition of nitrogen is not sufficient, and thus, biological nitrogen fixation is a major contributor of the nitrogen-input and thus plays an important role for terrestrial arctic ecosystems. Free-living, moss-associated (epiphytic) and symbiotic (lichen) cyanobacteria are considered to be the main source of biologically fixed nitrogen in polar regions. As other microbial processes, also cyanobacterial nitrogen fixation is strongly influenced by abiotic factors. In case of cyanobacteria these factors may be soil water content, soil temperature and the quality and quantity of solar radiation. Models of future climate predict a significant changes in the climate conditions in the Arctic, which in turn may affect the cyanobacterial nitrogen fixation activity.
To understand how possible climate changes might affect nitrogen fixation and primary production in terrestrial arctic ecosystems we measured the long-term effect of enhanced UVB radiation, and the effect of changes in the water, temperature, and light regime on the nitrogen fixation activity in arctic vegetation on Svalbard, High Arctic. Moss-associated cyanobacteria exposed to experimentally enhanced UVB radiation (representing a 15% ozone depletion) for six years showed a more than 40% reduction of their nitrogen fixation activity compared to controls. Moreover, temperature, soil water content and light intensity also had a strong and clear effect on the nitrogen fixation activity. However, our results showed that only severe changes in soil temperature and light intensity will have a significant effect on the nitrogen fixation activity in high arctic soils, whereas even slight changes of the water content may clearly affect this process.
Abstract Categories: Biological Feedbacks, Student Poster
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