Browsing by Author "Laakkonen, Aliisa"

Peatlands are complex ecosystems that not only respond to external changes but also influence their environment. Permafrost peatlands have an important role in the global carbon (C) cycle as they store about 200 Pg of C. As permafrost thaws this C can be released either as methane (CH4) or carbon dioxide (CO2). In addition to these peatlands also emit nitrous oxide (N2O). Climate warming may change this sink-source balance of peatlands. Hydrological conditions are an important factor in peatland C dynamics. As permafrost thaws it can shift these ecosystems towards wetter or dryer conditions. Peat decomposition under dry conditions can have a strong positive feedback to climate change due CO2 emissions. Though wetter conditions can increase CH4 emissions. Through topography and hydrology, permafrost also affects vegetation dynamics. In this thesis I am examining peat profiles collected from two subarctic permafrost peatlands located in Kevo, Finland and Karlebotn, Norway. The profiles included an un-frozen active layer profile and a permafrost sample collected from inside a palsa mound. These samples were analysed for vegetation composition and peat properties (C and N content, C/N ratio and bulk density), they were also 14C dated and incubated. The purpose was to simulate a warmer climate to which these ecosystems will be exposed to in the future and observe how they will respond. The observations focused on the three most common GHGs of peatlands, CH4, CO2 and N2O. The permafrost samples showed potential for CH4 and CO2 emissions, whereas the active layer only emitted CO2. The CH4 emissions were interpreted to represent old CH4, whereas the CO2 was interpreted to be produced by the peat.