4.1 The effect of open-water pools on the net ecosystem CO2 exchange of a boreal peatland

Monday, 20 June 2016: 3:30 PM
Orion (Sheraton Salt Lake City Hotel)
Luc Pelletier, McGill University, Saint-Anne-de-Bellevue, QC, Canada; and I. B. Strachan, N. T. Roulet, and M. Garneau

Peatland open-water pools are a common feature on temperate, boreal and subarctic peatlands. A limited number of studies, focusing mainly on the growing season, have shown pools to represent net sources of carbon dioxide (CO2) to the atmosphere. However, their impact on the net ecosystem carbon dioxide (NEE-CO2) is poorly understood. Considering the magnitude of the CO2 flux from these water bodies, it is uncertain whether peatlands with open water pools are net sink for CO2. 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 by such method can be larger than the fluxes. In this study, we measured the annual CO2 exchange from peatland open-water pools, we assessed if the presence of pools has a measurable impact on the peatland NEE-CO2, and we evaluated the CO2 sink potential. We measured open water CO2 flux using a combination of the headspace technique and a non-dispersive infrared CO2 sensor. NEE-CO2 was measured using eddy covariance. Our results confirm that the peatland open-water pools are a significant source of C to the atmosphere, with an annual release of 103 g C m-2, of which 15% was released during the ice-met period. The CO2 release from the pools had a measureable impact on the NEE-CO2; an increase in pool contribution to the ecosystem CO2 fluxes results in a reduction in both ecosystem level maximum gross photosynthesis and ecosystem respiration. Despite significant CO2 loss from the pools, we found the overall peatland to be a net sink for CO2 for the measurement period.

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