Do pool surface area and depth control CO₂ and CH₄ fluxes from an ombrotrophic raised bog, James Bay, Canada?

Abstract

The relationship between the exchange of CO 2 and CH 4 and the surface area and depth of 16 pools on a northern peatland was investigated over 2 years. Differences in carbon gas emissions were found, with small, shallow pools (<1000 m 2 , <0.45 m) having consistently larger CO 2 and CH 4 fluxes of 0.35 ± 0.47 g C m −2 d −1 and 0.31 ± 0.69 g C m −2 d −1 , respectively. Average CH 4 fluxes decreased with increasing pool depth and were between 1 and 5 times larger from shallow pools (0.3 m, p < 0.001) than from deeper pools (0.7 m). Average CO 2 fluxes also generally decreased with increasing pool depth and were between 1 and 4 times larger from shallower pools (0.3 m, 0.45 m, p < 0.004) than from deeper pools (0.75 m). Average pool C‐CO 2 losses in 2005 were approximately 3 to 30 times lower (0.11 g C m −2 ) than dark respiration CO 2 losses from the adjacent vegetated section of the peatland. All pools, regardless of size, were atmospheric sources of CO 2 and CH 4 over the sampling period at an average emission ratio of 1C‐CO 2 :1.5C‐CH 4 , with total carbon losses of 20.1 g C m −2 and 29.6 g C m −2 over 2004 and 2005. Consistently larger fluxes to atmosphere of both CO 2 and CH 4 from shallow pools (<0.45 m) suggest that enhanced decomposition could be occurring, accounting for the differences in carbon gas exchange.