Snow-packing as a potential harmful factor on Picea abies, Pinus sylvestris and Betula pubescens at high altitude in northern Finland

Snow-packing, a combination of ice, hoarfrost and snow on trees, and the su bsequent tree damage by snow, were estimated on Norway spruce (Picea abies) , Scots pine (Pinus sylvestris), and pubescent birch (Betula pubescens) in the winter of 1993-94 in southern Lapland, northern Finland, near the local alpine timberline around 400 m a.s.l. Snow-packing on each fully sized tre e increased from a few hundred kilograms at 150-250 m a.s.l. to a maximum o f 3290 kg at 300-350 m a.s.l. At 300 m a.s.l., snow-packing Der metre of st em increased from 30 to 50 kg on trees < 5 m in height up to 180-200 kg on 20-m trees. There was 300000-480000 kg/ha of snow accumulated on tree crown s. No stem breakage by snow-packing occurred at or below 250 m a.s.l., wher eas at 290-350 m a.s.l., 0-46%, 39-100%, and 0-33% of the spruce, pine and birch trees, respectively, had broken tops. Birch appeared to be the most r esistant and pine the most susceptible to snow breakage.