Annual CO2 exchange between a nutrient-poor, minerotrophic, boreal mire and the atmosphere

[1] Mires are key landscape elements at high latitudes and have certainly accumulated carbon during the Holocene, but their current carbon balance at the present time is very unclear. The major carbon flux is the land-atmosphere CO2 exchange and full-year data are still limited. Here we present data from 3 a (2001-2003) of continuous Eddy Covariance measurements at Degero Stormyr (64 degrees 11'N, 19 degrees 33'E) an oligotrophic, minerotrophic mire in Sweden. The climate at the site is defined as cold temperate humid, with 30-a annual precipitation and temperature means of 523 mm and +1.2 degrees C, respectively, while the mean temperatures in July and January are +14.7 degrees C and -12.4 degrees C, respectively. The length of the vegetation period was 153 +/- 15 d during the measured years. The minerotrophic mire represented a net sink for the vertical exchange of atmospheric CO2-C during the 3 a, with an average net uptake of 55 +/- 7 g ( mean +/- SD) CO2-C m(-2) a(-1). The growing season average uptake was 92 +/- 10 g CO2-C m(-2), of which approximately 40% ( 37 +/- 5 g CO2-C m(-2)) was lost during the nongrowing season. The daily average uptake over the growing season was 0.65 +/- 0.57, 0.73 +/- 0.61, and 0.68 +/- 0.62 g CO2-C m(-2) d(-1) in 2001, 2002, and 2003, respectively. The daily average net uptake for the month with highest uptake was 1.10 +/- 0.33, 1.11 +/- 0.63, and 1.22 +/- 0.55 g CO2-C m(-2) d(-1) in July 2001, July 2002, and June 2003, respectively. The daily average efflux during the nongrowing season was 0.14 +/- 0.28, 0.15 +/- 0.20, and 0.20 +/- 0.19 g CO2-C m(-2) d(-1) in the years 2001, 2002, and 2003, respectively