CO2 FLUXES FROM PEAT IN BOREAL MIRES UNDER VARYING TEMPERATURE AND MOISTURE CONDITIONS

1 CO2 emissions in boreal peatlands were measured during two seasons o n various mire site types representing different nutrient statuses and water tables. In order to examine the long term effects of water tabl e draw-down on the CO2 fluxes, the sites also included 25-50-year-old drainages. 2 On virgin sites the lowest CO2 fluxes were measured at om brotrophic sites dominated by Sphagnum fuscum (78-127 mg CO2 m(-2) h(- 1) at 12 degrees C, 60-200 g CO2-C m(-2) year(-1)) and the highest CO2 fluxes were at ombrotrophic sites with abundant understorey vegetatio n (183-259 mg CO2 m(-2) h(-1) at 12 degrees C, 290-340 g CO2-C m(-2) y ear(-1)). 3 Lowering of the water table by 1 cm increased CO2 fluxes b y an average of 7.1 mg CO2 m(-2) h(-1) at 12 degrees C and 9.5g CO2-C m(-2) year(-1). In some cases the effect of ditches on the water table , and correspondingly on CO2 fluxes, was small. However, effective dra ining caused approximate to 100% increase in CO2 fluxes. Drainages had higher CO2 fluxes compared with virgin subsites at the same temperatu re and water table. 4 The effect of temperature on CO2 fluxes depended on the water table, the average Q(10) value being 2.9 with water tabl es of 0-20 cm and 2.0 with water tables below 20 cm. 5 CO2 fluxes are compared with primary production figures, and peat carbon stores and t he carbon balance in changing climate are discussed.