Impact of fire and frost drought events on vegetation greenness and albedo in Subarctic Scandinavia

Sammanfattning: With climate change, the frequency in climate extremes such as drought, heavy rainfalls, and extreme temperatures is predicted to increase. These extremes can potentially stress and damage vegetation over large areas, leading to altered carbon cycle, vegetation greenness, albedo, and shifted species composition. This study focuses on two different types of extreme events; frost drought caused by winter warming and fires. The first aim was to study how these events affect vegetation greenness and albedo in the Subarctic region of Norway and Sweden. A second aim was to test whether the effects differ between land cover categories. The before-after-impact approach was applied to determine the effect of the events. When studying all sites, the results show no impact for neither albedo nor vegetation greenness as caused by the fire events. However, when studying the impact for the different land cover categories, the vegetation in the category Mosaic tree shrubs, herbaceous cover shows a decrease in albedo after the fire events. No impact was found for the categories Broadleaved forest and Needleleaved forest. For the frost drought events, an increase in albedo was found when analysing all sites. When studying the different land cover categories, no impact on albedo nor vegetation greenness as caused by the frost drought events was found. This result indicates that the impact of frost drought events on albedo must be further investigated, especially since the effect of frost drought on albedo is poorly documented. Also, this study was focused on the effect of single fire and frost drought events. However, how vegetation will be affected by multiple extreme events of the same and different types interacting with each, as well as increased frequency in extreme events, must be further studied.