| Summary: | Carbon is stored in natural Earth system reservoirs such as the crust, the atmosphere, the soil, the ocean and the phytomass, and naturally fluctuates in between these pools at different time-scales. However, due to human activities such as burning of fossil fuel and deforestation has the organic carbon content in the atmosphere in the form of CO2 increased by a third over the last century, triggering a climate warming. Increased air temperatures have the capability to further alter the carbon cycle, hence the size of and the fluctuations between reservoirs. Current concerns regarding permafrost regions is the thawing of permafrost making organic matter available for decomposition, during which carbon is released to the atmosphere as greenhouse gases, acting as a positive feedback to the warming climate. A warming climate additionally alter the nature of these environments through expansion of shrub and forest stands, which entails an increase of carbon stored within the phytomass compared to present levels. These concerns are especially valid for subarctic environments, which are vulnerable to climate warming. However, potential alterations in carbon storage in subarctic areas are difficult to project due to limited knowledge regarding their size. Hence, it is of interest to conduct more field sampling in these environments to obtain proper estimates. The main objectives with this thesis were to determine the carbon storages within the phytomass and the soil in two subarctic study areas, Abisko in northern Sweden and Utsjoki in northern Finland. The objectives were achieved through a stepwise process. First, field sampling was conducted at sites representing different land cover classes. The tree carbon was determined through allometric equations, i.e. relating physical properties of trees to biomass. The sampled field layer phytomass was dried and weighted. The carbon corresponds to half of the dry phytomass weight. The carbon in the soil samples was determined through dry bulk density, loss on ignition and ...
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