Greening och browning i Abisko 1986-2018

Abstract

Verified studies show a trend in warming of global mean temperatures. This warming trend affects the Arctic region with longer growing seasons and increased photosynthetic activity which is linked to greening. Changes in precipitation during the summer have instead reduced the photosynthetic activity which has been linked to browning. Greening is when vegetation increases and browning when it decreases. To study greening and browning the index NDVI (Normalized Difference Vegetation Index) is used to measure the plant productivity and biomass as well as identifying vegetation and non-vegetation with the help of satellite images from three Landsat satellites. The purpose of this study is to use satellite data with high spatial resolution to see if there has been a change in the vegetation in Abisko the last 32 years, that is greening or browning. Furthermore, it is studied whether there is any correlation between changes in NDVI and elevation, which vegetation types that exist in areas with greening and browning, as well as any correlation between changes in vegetation linked to air temperature and precipitation. Satellite data over Abisko between the years 1986 and 2018 has been analyzed and this shows that a greening has occurred in Abisko over the past 32 years. The result shows changes in NDVI that vary between the years with both greening and browning. Significant correlations could be seen between differences in NDVI and changes in mean temperature during winter and spring, as well as between changes in NDVI and elevation. The vegetation types mountain birch of moss type and willow have a greater distribution in the areas of greening than in the areas of browning. Further studies are needed to examine more closely the underlying causes to the changes in vegetation.