Karaktäristiken hos strukturmarken på olika altitud i Abiskoområdet – en koppling till klimat och komplex systemteori

Detta är en avhandling från Uppsala : Kulturgeografiska institutionen, Uppsala universitet

Sammanfattning: Subarctic and alpine areas are sensitive to climatic change when they lie at the margin of permafrost occurrence. Patterned ground in such areas is generated from an interplay among different mechanisms such as temperature, hydrology, soil texture, snow cower and vegetation. The aim of this study is to describe the connection between patterned ground characteristics and altitude and to evaluate the impact different variables have on the appearance of patterned ground. To understand these interactions is a discussion of self-organization processes, threshold effects and feedback mechanisms essential. In this investigation, characteristics of patterned ground are examined along an elevation gradient in the Abisko area in Northern Sweden. The study is limited to formations that are categorized into non-sorted circles on flat ground. To detect significant correlations between the characteristics of patterned ground and altitude nine places between 400 and 1400 m above sea level with at least 100 m difference in altitudes were investigated. These sites were categorized into six ridges and three sinks to evaluate the importance of topography.Non-sorted circles have less dwarf shrub, more moss-lichen cover and more cryptogam crust than surrounding ground. Outside the formations the amount of dwarf shrub decreases and the moss-lichen cover increases above 1000 m above sea level. At the highest altitude also a cryptogam crust is occurring around non sorted circles. Significant correlations exist between declining ground temperature and altitude, declining distance between non-sorted circles and altitude, and less dwarf shrub vegetation on non-sorted circles and altitude. These relationships are expected and can be connected to cryoturbation and abiotic stress. Shorter distance between formations can be linked to increased abiotic stress and less coverage soil stabilizing dwarf shrub vegetation. Formations are larger in sinks than ridges and surrounded by less dwarf shrub and more moss-lichen vegetation. This difference can be explained by longer snow duration, humid soil conditions and prolonged freezing processes in ground.Non-sorted circles on an east aspect slope ridge at about 900 meters altitude is characterized by low soil temperatures, high soil moisture, low height and low coverage plants. Around these formations is a well-developed ground cover consisting primarily of dwarf shrub vegetation. These observations are a sign of positive interaction resulting in strong self-generating soil movements that have exceeded a threshold when breaking through vegetation cover. Low soil temperature and high moisture at the time of measurement might be explained by existing ice-front and free water convection. These patterned ground characteristics can be linked to permafrost, the inflow of water from higher leeward slopes and thin snow cower.