摘要 : Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO_2), methane (CH_4) and... 展开 Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO_2), methane (CH_4) and nitrous oxide (N_2O) change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C). We measured CO_2 exchange with the eddy covariance (EC) method above a drained nutrient-poor peat-land forest in southern Finland for 16 months in 20042005. The site, classified as a dwarf-shrub pine bog, had been ditched about 35 years earlier. CH_4 and N_2O fluxes were measured at 2-5-week intervals with the chamber technique. Drainage had resulted in a relatively little change in the water table level, being on average 40 cm below the ground in 2005. The annual net ecosystem exchange was -870 + 100g CO_2 m~(-2)yr~(-1) in the calendar year 2005, indicating net CO_2uptake from the atmosphere. The site was a small sink of CH_4 (-0.12 g CH_4 m~(-2) yr~(-1)) and a small source of N_2O (0.10 g N_2O m~(-2) yr~(-1)). Photosynthesis was detected throughout the year when the air temperature exceeded -3℃. As the annual accumu-lation of C in the above and below ground tree biomass (175 ± 35 g C m~(-2)) was significantly lower than the accumu-lation observed by the flux measurement (240 ± 30 g C m~(-2)), about 65 g C m~(-2) yr~(-1) was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry-drainage may significantly increase the CO_2uptake rate of nutrient-poor peat-land ecosystems. 收起