Browsing by Author "Pyykkö, Petteri"

The boreal forest zone covers approximately 3% of Earth's non-frozen land area and contains large quantities of carbon. Methane (CH4) emissions originating from the forested peatlands are not large but their contribution can change due to future’s climate change. This makes it important to study how boreal forests respond to changing climatic conditions. Methaneproducing archaea present in these ecosystems produce CH4 under anaerobic conditions. Soil CH4 emissions are controlled by the depth of the anaerobic and aerobic layers, which are affected by variations in water table level (WTL). Here I addressed the role of trees, growing in drained peatland forests, on the CH4 balance, and discussed what could be the driving environmental variables affecting tree CH4 exchange. The Lettosuo site is a nutrient rich drained peatland forest in southern Finland. The measurement setup: 1) control plot 2) partially harvested plot without Scots pines to decrease evapotranspiration, which leads to higher WTL. The partial harvest at Lettosuo simulates real world selective cutting giving more value to this study. Tree stem fluxes were measured over two summers (May-Sept 2016 and 2017). All the species emitted CH4 from the stems and the emissions decreased in the order: downy birches, Scots pines, Norway spruces. According to the linear mixed-effects model, WTL significantly affected the CH4 emissions from the stems of downy birches (p<0.05). Also different chamber designs (box-shaped and cylinders) were used during the measurement campaign. We found that observed CH4 fluxes differ from each other largely depending on the chamber design.