Fluxes of carbon dioxide (CO2) and methane (CH4) from a poor boreal bog and an oligotrophic fen site were measured during a growing season and the following winter in eastern Finland. In addition to these intensively studied sites, some flux data was collected from other sites including natural peatlands and those drained for forestry and agriculture. From the drained sites, also nitrous oxide (N2O) emissions are re-ported. The flux data was collected using both closed chamber method and by calcu-lating gas diffusion along the concentration gradient through the snowpack. Calcula-tion of gas emissions with snowpack diffusion method gave results well comparable with those obtained with flux chamber technique when the snowpack was homoge-nous. However, in conditions of clearly layered snow profile, the snowpack diffusion method gave much higher estimates than the chamber method.

Wintertime CH4 emissions from the bog site were lower than those from the fen site, reflecting the characteristic methane production capacity of the peatland site. Weak N2O emissions were observed in the drained minerotrophic fen sites and the former fen drained for grassland. Methane consumption continued in winter in well-drained forested fen sites. Winter emissions of CH4 from natural peatlands seemed to follow the emissions of the preceding summer, indicating a dynamic substrate or methane pool in the sediment after the growing season. Similar pattern was observed as CO2 release in oxidative decomposition of organic matter. Emissions of CO2 and CH4 cor-related with peat temperature showing a slight midwinter maximum in the bog and fen sites with increasing surface peat temperature probably due the isolating properties of the c. 70 cm snowpack.

Jukka Alm
Department of Biology, University of Joensuu
P.O. Box 111, FIN-80101 Joensuu, Finland
Tel:	+358 73 1511 3502
Fax:	+358 73 1511 3590
email: Alm@joyl.joensuu.fi