The dynamic carbon balance of a southeastern New Hampshire wetland was constructed for the 1994 growing season using a light-dark box sampling method. Net ecosystem exchange (NEE) (n=414) and ecosystem respiration (n=234) measurements were made at the 1.7 ha Sphagnum spp. dominated poor fen. The NEE rates ranged from -192 to 492 mg C m-2 h-1 and the ecosystem respiration measurements were between -10 and -365 mg C m-2 h-1. The negative values represent a loss of carbon from the wetland system. NEE and respiration data were used to derive photosynthesis rates of the vegetation at the study site. A simple model, using hourly averages of photosynthetically active radiation, and air and soil temperatures to generate hourly rates of photosynthesis and respiration, was constructed to interpolate the carbon cycling rates at this fen through the entire 1994 growing season. Results of the carbon balance model suggest that the wetland lost an estimated 145 g C m-2 for the 9 month modeling period (April through December). The 1994 climate season was warmer (+1.15 ¿C/month) and drier (-12.3 cm) than the 30 year normals for Durham, New Hampshire, the nearest meteorological station. These data suggest that if future climate change brings about warmer temperatures and lower water tables in peatland soils, positive climatic feedback leading to substantial releases of CO2 from boreal and subarctic peatlands is probable.¿ 1997 American Geophysical Union