The station Zackenberg, is located in central Northeast Greenland within the area of Greenland National Park. From the west, north and east valley is surrounded by mountains (>1000 m a.s.l.) and the southern margin is set by the Young Sund fjord. Study site is characterized by high arctic climate conditions, the ground is covered by snow for about 236 days per year. Study area is underlain by continuous permafrost with active layer depth reaching ca. 0.85 m, increasing by ca. 0.01 m every year (Lund et al. 2014). The length of the growing season is highly variable and dependent on the day of the snowmelt. The peak of vegetation greenness generally takes place in late July/early August and the end of the growing season usually occurs in early September.