The Impact of Open-Water Pools on the Net Ecosystem CO2 Exchange of a Boreal Peatland

English Abstract:

Peatland open-water pools are a common feature on temperate, boreal and subarctic peatlands but their impact on the net ecosystem carbon dioxide exchange (NEE-CO₂) is poorly understood. A limited number of studies using measurements made solely during the growing season have shown pools to represent net sources of CO₂ to the atmosphere. To date, the evaluation of the CO₂ budget of peatlands with pools has only been explored through spatial extrapolation and temporal interpolation of point measurements made using static chambers; the errors introduced can be larger than the fluxes. In this study, we evaluated the annual CO₂ exchange from peatland open-water pools using a combination of methods (headspace technique and non-dispersive infrared CO₂ sensor) to obtain a complete annual surface to atmosphere CO₂ exchange from pools, including ice melt emissions. Simultaneously, we assessed if the presence of pools has a measurable impact on the peatland NEE-CO₂ using a combination of eddy covariance (EC) measurements and source area analysis. Our results confirm that the peatland open-water pools are a significant source of C to the atmosphere, with an annual release of 99 g CO₂-C m^-2, of which 15% was released during the ice-met period. The source area analysis performed on the EC tower data shows that an increase in pool contribution to the ecosystem CO₂ fluxes results in a reduction in both ecosystem level maximum gross photosynthesis and respiration. Despite significant CO₂ loss from the pools, we found the overall peatland to be a net sink for CO₂ for the measurement period.