In a field study, we examined the relationship between vegetation, abiotic factors and the CO exchange dynamics of a cut-away peatland 20 years after production had ended. The main objective was to determine the effect of rewetting on the CO exchange dynamics, measured separately in Eriophorum vaginatum tussocks and intertussocks (almost non-vegetated surfaces) using closed-chamber techniques, one growing season before and three growing seasons after the rewetting treatment. Rewetting lowered total respiration (R ) and increased gross photosynthesis (P), which resulted in a higher incorporation of CO into the system. The seasonal CO balance for the almost continuously submerged section of the rewetted site became positive 2 years after rewetting (9.1 g CO-C m), and it was still higher in the 3rd year (64.5 g CO-C m), i.e. the system accumulated carbon. In the driest section of the rewetted site the seasonal balance increased strongly, but the balance was still negative during the 3 years following rewetting with losses from the system of 44.1, 26.1, 38.3 g CO-C m in 1995, 1996 and 1997 respectively. At the control site seasonal balance during 1995-1997 varied between ecosystem C losses of 41.8 and 95.3 in an area with high Eriophorum cover and between 52.1 and 109.9 g CO-C m with lower cover. Simulation of a cut-away peatland with dense Eriophorum vegetation (Eriophorum cover 70%) showed that if the water level (WT) is low, the seasonal CO balance of the ecosystem can reach the compensation point of no net C change (P = R) only if weather conditions are favourable, but with a high WT the seasonal CO balance would be positive even under varying weather conditions. It can be concluded that with dense Eriophorum vegetation a restored cut-away peatland acts as a functional mire and becomes a sink for atmospheric CO.

Summary We measured a cut‐away peatland's CH4 dynamics using the static chamber technique one year before and two years after restoration (rewetting). The CH4 emissions were related to variation in vegetation and abiotic factors using multiple linear regression. A statistical model for CH4 flux with cottongrass cover (Eriophorum vaginatum L.), soil temperature, water level, and effective temperature sum index as driving variables explained most (r2 = 0.81) of the temporal and spatial variability in the fluxes. In addition to the direct increasing effect of raised water level on CH4 emissions, rewetting also promoted an increase of cottongrass cover which consequently increased carbon flux (substrate availability) into the system. The seasonal CH4 dynamics in tussocks followed seasonal CO2 dynamics till mid August but in late autumn CH4 emissions increased while CO2 influxes decreased. The reconstructed seasonal CH4 exchange was clearly higher following the rewetting, although it was still lower than emissions from pristine mires in the same area. However, our simulation for closed cottongrass vegetation showed that CH4 emissions from restored peatlands may remain at a lower level for a longer period of time even after sites have become fully vegetated and colonized by mire plants.

Summary1. Components of the CO 2 balance for a drained minerotrophic fen and a drained ombrotrophic bog were measured for permanent plots using static chamber techniques for 1 year before and 2 years after a rewetting treatment in part of both sites. During the same period, changes in ground and bottom layer vegetation composition were monitored. 2. After the treatment, the water table rose, the average increase being 25 cm for the fen site and 20 cm for the bog site. In the untreated areas the average water table remained at the pretreatment level.3. There was a clear change in vegetation composition in the rewetted area of the fen site where the cover of cottongrass Eriophorum vaginatum L. increased drastically. The change in vegetation composition seemed to be dependent on the nutrient status of the sites, being faster at the more nutrient-rich fen site. 4. The rates of CO 2 eux from the soil surface decreased on those rewetted plots where all vegetation had been removed. In 1996, the CO 2 eux rates from the soil surface of the untreated plots were about twice as high as from the rewetted plots with a high water table. 5. The change in water table levels and vegetation composition aected the seasonal (mid-May to end of September) CO 2 -C balances. For the rewetted area of the fen site, the CO 2 -C balance varied from 162 to 283 g m ±2 , being greatest in a plot with dense E. vaginatum cover and a high water table. For the rewetted area of the bog site, the CO 2 -C balance varied from 54 to 101 g m ±2 , being greatest in a hollowlevel plot with a high water table and mire vegetation. For the untreated areas, the CO 2 -C balance was close to zero (3 g m ±2 at the bog site) or negative (±183 g m ±2 at the fen site), when carbon ®xation by the tree stand was omitted. 6. The results are encouraging from the practical point of view as restoration of both fen and bog sites initiated vegetation succession and CO 2 -C balance development towards those of pristine mires.

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