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

Carbon dioxide (CO2) and methane (CH4) 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 CO2 flux, and CH4 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 CO2 m(-2) d(-1) (respiration), -1056-100 mmol CO2 m(-2) d(-1) (net CO2 exchange), and 0.1-36.8 mmol CH4 m(-2) d(-1) (a positive value represents efflux to the atmosphere). Respiration and CH4 emission were significantly correlated with 5 cm soil temperature. Annual respiration and CH4 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 similar to0.7 mol m(-2) yr(-1) determined from C analyses of a peat core collected from the wetland.