CO 2 and CH 4 flux between a boreal beaver pond and the atmosphere

The surface‐atmospheric exchange of CO 2 and CH 4 was measured continuously using the flux gradient approach from a beaver pond in the northern study area of the Boreal Ecosystem‐Atmosphere Study between May 22 and September 19, 1994. The beaver pond was a large source of CO 2 and CH 4 for the entire study period. The half‐hourly mean flux of CO 2 and CH 4 ranged from −0.498 to 1.135 mg CO 2 m −2 s −1 and from −0.805 to 37.5 μg CH 4 m −2 s −1 , respectively, while the seasonal mean fluxes were 0.072±0.095 mg CO 2 m −2 s −1 and 1.26±1.87 μg CH 4 m −2 s −1 . The beaver pond rarely took up CO 2 . There was a large flux of both gases during the daytime. This increase is related to the transfer of the gases rather than to specific controls on production. The total efflux of CO 2 and CH 4 for the 120 days of the study was 678 g CO 2 m −2 and 11.3 g CH 4 m −2 , or 183 and 8.4 g C m −2 , respectively. When the measurements ceased, the sediment temperatures were >10°C, so it is reasonable to expect that the fluxes of CO 2 and CH 4 continued into the late fall. This indicates that the beaver pond released more than 200 g C m −2 yr −1 .