Letter abstract

Nitrous oxide is a potent greenhouse gas whose concentration is increasing in the atmosphere¹. So far, the highest terrestrial nitrous oxide emissions have been measured in agricultural and tropical soils^{2, 3}, and nitrous oxide emissions from northern natural soils have been considered negligible^{4, 5}. Pristine tundra, one of the largest natural land cover types in the world, is a mosaic of different surface types including bare surfaces created by cryoturbation^{6, 7}. Here we used a static chamber method to measure nitrous oxide emissions from the discontinuous permafrost zone in subarctic East European tundra. We show that nitrous oxide emissions from bare peat surfaces in the region, known as peat circles, range between 0.9 and 1.4 g nitrous oxide m^-2 from June to October, and are equivalent to those from tropical and agricultural soils. Extrapolation of our data to the whole Arctic reveals that the emissions from these hot spots could amount to 0.1 Tg nitrous oxide yr^-1, corresponding to 4% of the global warming potential of Arctic methane emissions at present. Therefore, not only carbon, but also nitrogen stored in permafrost soils, has to be considered when assessing the present and future climatic impact of tundra.

¹Department of Environmental Science, University of Kuopio, PO Box 1627, FIN-70211 Kuopio, Finland.

²Department of Biological and Environmental Sciences, University of Helsinki, PO Box 27, FIN-00014 Helsinki, Finland.

³Institute of Biology, Komi SC UrD RAS, 197982 Syktyvkar, Russia.