Carbon gas exchange at a southern Rocky Mountain wetland, 1996–1998

Carbon dioxide (CO 2 ) and methane (CH 4 ) exchange between the atmosphere and a subalpine wetland located in Rocky Mountain National Park, Colorado, at 3200 m elevation were measured during 1996–1998. Respiration, net CO 2 flux, and CH 4 flux were measured using the closed chamber method during snow‐free periods and using gas diffusion calculations during snow‐covered periods. The ranges of measured flux were 1.2‐526 mmol CO 2 m −2 d −1 (respiration), −1056−100 mmol CO 2 m −2 d −1 (net CO 2 exchange), and 0.1–36.8 mmol CH 4 m −2 d −1 (a positive value represents efflux to the atmosphere). Respiration and CH 4 emission were significantly correlated with 5 cm soil temperature. Annual respiration and CH 4 emission were modeled by applying the flux‐temperature relationships to a continuous soil temperature record during 1996–1998. Gross photosynthesis was modeled using a hyperbolic equation relating gross photosynthesis, photon flux density, and soil temperature. Modeled annual flux estimates indicate that the wetland was a net source of carbon gas to the atmosphere each of the three years: 8.9 mol C m −2 yr −1 in 1996, 9.5 mol C m −2 yr −1 in 1997, and 9.6 mol C m −2 yr −1 in 1998. This contrasts with the long‐term carbon accumulation of ∼0.7 mol m −2 yr −1 determined from 14 C analyses of a peat core collected from the wetland.