Net ecosystem CO2 exchange in a boreal peatland, northern Manitoba

Abstract

Net ecosystem CO2 exchange (NEE) was measured by a chamber technique from June to September, 1994, at five peatland sites where the water table was close to the peat surface, ranging from ombrotrophic bog to minerotrophic fen, near Thompson, Manitoba. NEE measurements were made during three 10-14-day periods, and CO2 exchange relationships with photosynthetically active radiation (PAR), air and soil temperatures, and water table were used to model net ecosystem productivity (NEP) for the season. Daily NEE ranged from -3 to 5 g CO2-C m-2 d-1, with positive values indicating uptake by the land surface. Two of the sites became sources of CO2 during the late summer, associated with plant senescence and falling water tables. Average NEP for June to August ranged from 1.4 to 2.5 g CO2-C m-2 d-1. Both water table position and end-of-season above-ground sedge biomass were strong predictors of NEP during each measurement period, as well as over the June to August period. Sites with high NEP had high aboveground sedge biomass (75 to 100 g m-2) and low water tables (seasonal average -5 to -10 cm).