| Summary: | The Arctic region has experienced significant warming in the past decades and according to predictions further increases in air temperatures and precipitation will occur during the 21st century. Recent changes in climate have had widespread implications for the permafrost around the Arctic. Shorter periods of snow covering the Arctic regions significantly reduce the average annual albedo which dramatically increases the amount of energy being absorbed by the ground surface. In addition, the amount of snow has increased which results in even further warming of the ground through insulation during the winter. Warmer ground temperatures increase the available amount of organic material stored in the formerly frozen ground when the active layer (i.e. the upper layer that thaws and refreezes annually) becomes thicker. This can potentially lead to additional releases of greenhouse gases resulting in even further regional warming and permafrost degradation with implications for the global climate. The Arctic vegetation has also changed due to higher air temperatures and altered precipitation patterns. Future predictions suggest more productive vegetation over the Arctic. This will likely increase the dominance of trees and shrubby vegetation leading to reductions in moss vegetation. Sub-arctic palsa mires in northern Sweden are experiencing a different shift in vegetation with higher graminoid abundance and declining shrub coverage due to increasing wetness. A change in the type of vegetation i.e. a change in plant functional types can alter the albedo together with the shading-, the evapotranspiration-, the snow trapping- and insulation potential. All these factors have the potential to change the ground temperature and the soil moisture content which affect the underlying permafrost. Changes like this have already been observed at the margin of where permafrost can exist, for example in the Abisko area in northernmost Sweden. This report presents results from an experiment where different plant functional types ...
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