87 SUO 53(3–4), 2002 © Suoseura — Finnish Peatland Society ISSN 0039-5471 Helsinki 2002 Suo 53(3–4): 87–96 Fluxes of nitrous oxide on natural peatlands in Vuotos, an area projected for a hydroelectric reservoir in northern Finland Jari T. Huttunen, Hannu Nykänen, Jukka Turunen, Olli Nenonen and Pertti J. Martikainen Jari T. Huttunen, Hannu Nykänen and Pertti J. Martikainen: Research and Develop- ment Unit of Environmental Health, Department of Environmental Sciences, Bioteknia 2, University of Kuopio, PO Box 1627, FIN-70211 Kuopio, Finland. Email: jari.huttunen@uku.fi. Jukka Turunen: Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, H3A 2K6 Canada. Olli Nenonen: Kemijoki Ltd., Valtakatu 9-11, FIN-96101 Rovaniemi, Finland. Nitrous oxide (N 2 O) fluxes were measured on ten natural minerotrophic peatlands in an area planned for a hydroelectric reservoir (Vuotos) in northern Finland. The mean N 2 O fluxes from the sites with mean water tables from –25 to 3.4 cm (negative below the peat surface) ranged from –30 to 230 μg m –2 d –1 during summer 1994. At the driest site, the herb-grass spruce mire with the mean water table at –38 cm, the mean sum- mertime N 2 O emission was 940 μg m –2 d –1 in 1994, attributable to the increased N 2 O release at low peat temperatures in autumn. A similar increase in the N 2 O emissions was not found in 1995, as the measurements were finished before the peat started to freeze. The mean N 2 O fluxes at the sites correlated negatively with the mean water table levels. The peatlands in the northern boreal zone are unlikely important sources of atmospheric N 2 O in their natural state. The planned reservoir would barely have large long-term N 2 O emissions from the pelagic zone, but the importance of tempo- rally flooded areas in the postflood N 2 O release is uncertain similar to the short-term emissions following the flooding. Keywords: Northern boreal peatlands, climate warming, flooding, global change, green- house gas emission, hydro dam Introduction Nitrous oxide (N 2 O) is a radiatively active green- house gas in the atmosphere (Khalil 1999, IPCC 2001a) and it also contributes to the destruction of stratospheric ozone (Cicerone 1987). Globally, soils represent a major source of N 2 O emissions to the atmosphere (Khalil 1999). Nitrous oxide is produced in soils mainly by two microbial proc- esses, nitrification and denitrification (Davidson & Schimel 1995). Denitrification can also con- sume N 2 O in soils (Schiller & Hastie 1994, Regina et al. 1996). In general, natural northern wetlands have