Carbon dioxide exchange fluxes of a boreal peatland over a complete growing season, Komi Republic, NW Russia

The carbon pool of peatlands has been considered as potentially unstable in a changing climate. This study is the first presenting carbon dioxide (CO2) net ecosystem exchange, CO2 efflux due to ecosystem respiration and CO2 uptake by gross primary production over a complete growing season for different microforms of a boreal peatland in Russia (61A degrees 56'N, 50A degrees 13'E). CO2 fluxes were measured using the closed chamber technique from the 25th April in the period of snow melt until the end of the vegetation period and the first frost on the 20th October 2008 at seven different microform types: minerogenous and ombrogenous hollows, lawns and hummocks, respectively, and Carex lawns situated in a transition zone between minerogenous and ombrogenous mire parts. The total number of chamber flux measurements was 5,517. Ombrogenous hummocks and lawns were sources of CO2 over the investigation period whereas hollows and minerogenous lawns were CO2 sinks. Some plots of Carex lawns and minerogenous hummocks were sinks while other plots of these microform types were sources. The CO2 fluxes were characterised by large variability not only between the microform types but also within the respective microform types. Of all microform types, the Carex, ombrogenous, and minerogenous lawns showed the highest variability in CO2 fluxes, which is probably related to a stronger within-microform heterogeneity in vegetation composition and coverage as well as in the water table level. Air temperature was one of the dominant controls on the CO2 flux dynamics. Water table and green area index were found to have strong influence on CO2 fluxes both within different patches of the same microform type as well as between different microforms.