Artikkelit jotka sisältää sanan 'CO2'

Data on greenhouse gas (GHG) exchange between water surfaces and the atmosphere above tropical peatland drainage canals are lacking in the literature. We quantified diffusion fluxes of CO2, CH4 and N2O between the water surface and the atmosphere for two typical reclaimed peatland sites. One site was an industrial pulp wood plantation in the Kampar Peninsula (Sumatra) and the other was an abandoned peatland area in Kalimantan (Borneo). Drainage canal fluxes were measured by using floating closed chambers during both the wet and dry seasons. Fluxes at the sites were determined across a range of conditions that were created by varying land use histories, and also by canal biotic environment and hydrological features. Gas fluxes in the canal systems were influenced by their respective surrounding peatland areas, the season, and canal management. Fluxes of all three gases were higher at the more recently reclaimed settled (undisturbed) canals of the Kampar site in comparison to the Kalimantan site. In general, the mean flux from the canals ranged from 9–16, 0.1–1.1 and 0–0.003 g m–2 d–1 for CO2, CH4 and N2O, respectively. A cumulative equivalent annual emission of these three GHGs from canals was nearly three times higher at the Kampar site (13.8 kg CO2 e m–2 y–1) than that at the Kalimantan site (4.8 kg CO2 e m–2 y–1). Mean fluxes of the three gases and the cumulative annual emission at the Kampar site were higher in the settled canals in comparison to the disturbed canals when both dry and wet season fluxes were calculated. The fluxes of CH4 and N2O especially decreased when canals had been recently cleaned (i.e. were in disturbed condition). In terms of their relative global warming potentials (GWP), CO2 was the most important of the three GHG’s both at the Kalimantan site settled canal (69% of the fluxes were attributed to CO2) and at the disturbed canals at the Kampar (82%) site, whereas CH4 dominated in settled canals at the Kampar site at 61% contribution to the total annual emission. CH4 contributed 31% to the total cumulative equivalent annual emission at the Kalimantan settled canal. N2O had only a minor role (0–2% of the cumulative fluxes) at the sites. On a unit area basis, GHG emissions from the drainage canals formed were generally higher emission sources in comparison to the surrounding peatland, and proportional contributions from the three GHG species to the total were more diverse in canals than on land.

• Jauhiainen, Jyrki Jauhiainen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland, e-mail: jyrki.jauhiainen@helsinki.fi Sähköposti: ei.tietoa@nn.oo
• Silvennoinen, Sähköposti: ei.tietoa@nn.oo

The vegetation and CO2 balance (difference between C02 fixation rate and respiration rate) in an abandoned harvested peatland in Aitoneva, Kihnio (62° 12'N, 23° 18'E) were studied during the summer of 1994. The daytime CO2 fluxes from sample plots representing different kinds of vegetation were measured using two different static chamber techniques. To investigate the compositional variation of vegetation and its relationship with CO2 balance, data on the vegetation of the sample plots was analysed by global non-metric multidimensional scaling (GNMDS). A total number of 20 plant species was observed on the sample plots. The dominant plant species was Eriophorum vaginatum L. The main variation in GNMDS were connected with colonization stage (total cover of vegetation). The C02 fixation rate varied between -56 and 1869 mg m-2 h-1 and the respiration rate varied between 34 and 1168 mg CO2 m-2 h-1. The CO2 fixation and respiration rate increased with increasing total vegetation cover. The highest respiration and the highest CO2 fixation rates were found in sample plots dominated by mature Eriophorum vaginatum tussocks. Those sample plots were the only ones having positive CO2 balance. Regression analysis indicated that the respiration rate depended on soil temperature. Variation in the water table had no influence on the respiration or the C02 fixation rate. Key words: CO2 balance, Eriophorum vaginatum, GNMDS, harvested peatland, plant colonization

• Tuittila, Department of Forest Ecology, P.O. Box 24, FIN-00014 University of Helsinki, Finland Sähköposti: ei.tietoa@nn.oo
• Komulainen, Sähköposti: ei.tietoa@nn.oo