| Summary: | Abstract Peat starts to decompose more rapidly after drainage, due to exposure to oxygen. While methane (CH₄) emissions tend to decrease after drainage, carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions from drained peatlands are considerable, especially the if the area is used for cultivation. Drainage and subsequent land management change the physical characteristics and thus hydrology and thermal conductivity of the soil, which affects greenhouse gas production. This thesis examined CH₄ and N₂O emissions and respiration from a peatland complex in Northern Finland, including a cultivated peatland, a forested peatland, a peat extraction site and a pristine mire. Chambers were used during the snow-free period and the snow gradient method during winter. Peat physical properties at the sites were also measured. The DRAINMOD model was used to assess measured peat hydraulic conductivity compared with the values needed to fit observed groundwater depth fluctuations. Effects of mineral soil content, drainage conditions and temperature on thermal conductivity of peat were examined and well-known equations for thermal conductivity of organic soils were tested. Respiration was highest in the cultivated study site, and this site and the peat extraction site were major sources of N₂O. The pristine site was a large source of CH₄ during the growing season. During winter, the peat extraction site and the cultivated site emitted CH₄. The results suggested that raising mean groundwater level from 60 cm to 40 cm could potentially mitigate the greenhouse gas emissions at the cultivated site. Soil hydraulic conductivity at the drained sites was found to be better predicted by land use type than by soil physical parameters. Hydraulic conductivity values needed for DRAINMOD were at least one order of magnitude higher than those observed in field measurements. This demonstrates the potential role of land use and macropore flow in controlling hydrological processes in peat soils. The samples with the highest mineral soil content ...
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