Snowfall during winter is decreasing and the period of snow cover shortening with climate change affecting the coupling between soil and air temperature and humidity. Snow cover isolates the ground and decreases the soil frost. Lack of snow cover may lead to deeper soil frost, and soil can remain frozen after the start of growing season, which prevents the water and nutrient uptake of trees. We study how decreasing snow cover affects trees. Massive snow shelters have been built in Hyytiälä Research Station for the purpose this autumn. This morning (15th of January) there is around -30°C temperature and 30 cm snow depth. In this experiment, we are studying how e.g. soil temperature, root growth, root respiration and tree water usage is affected by decreasing snow cover. Dr. Lauri Lindfors has the main responsibility of the measurements. Many people have been helping us in the field, and we look forward to see the first results next spring. The work is part of Anna Lintunen’s University of Helsinki funded 3 year’s research project on the Effects of wintertime physiology of trees on forest carbon sequestration in changing climate.