CO sub(2) fluxes from peat in boreal mires under varying temperature and moisture conditions

CO sub(2) emissions in boreal peatlands were measured during two seasons on various mire site types representing different nutrient statuses and water tables. In order to examine the long term effects of water table draw-down on the CO sub(2) fluxes, the sites also included 25-50-year-old drainages. On virgin sites the lowest CO sub(2) fluxes were measured at ombrotrophic sites dominated by Sphagnum fuscum (78-127 mg CO sub(2) m super(-2) h super(-1) at 12 degree C, 60-200 g CO sub(2)-C m super(-2) year super(-1)) and the highest CO sub(2) fluxes were at ombrotrophic sites with abundant under-storey vegetation (183-259 mg CO sub(2) m super(-2) h super(-1) at 12 degree C, 290-340 g CO sub(2)-C m super(-2) year super(-1)). Lowering of the water table by 1 cm increased CO sub(2) fluxes by an average of 7.1 mg CO sub(2) m super(-2) h super(-1) at 12 degree C and 9.5 g CO sub(2)-C m super(-2) year super(-1). In some cases the effect of ditches on the water table, and correspondingly on CO sub(2) fluxes, was small. However, effective draining caused approximately 100% increase in CO sub(2) fluxes. Drainages had higher CO sub(2) fluxes compared with virgin subsites at the same temperature and water table. The effect of temperature on CO sub(2) fluxes depended on the water table, the average Q sub(10) value being 2.9 with water tables of 0-20 cm and 2.0 with water tables below 20 cm. CO sub(2) fluxes are compared with primary production figures, and peat carbon stores and the carbon balance in changing climate are discussed.