Current issue: 53(1)
Snow cover and ground frost was studied in 29 forest stands in Southern and Central Finland in 1957–1959. The tree species influenced greatly accumulation of snow on the forest floor. Norway spruce (Picea abies (L.) Karst.) retains snow in its crown. In addition, snow and water falling from the branches compress the snow cover under the trees, and the ground freezes deeper because of the shallow snow cover. In the spring, the dense crown prevents rain and radiation reaching the ground, which remains cold longer. However, ground frost may protect spruce, which has a weak root system, from wind damages.
Scots pine (Pinus sylvestris L.) has similar, but milder, effects on snow cover within the forest. The crowns of pine seedlings and young trees pass snow easily, but later the crowns intercept it considerably. The lower branches are, however, high up and the snow is evenly spread on the ground. The deciduous trees intercept little snow and in the spring the snow smelts and the frozen soil thaws early. The snow conditions of deciduous forests are, however, changed by a spruce undergrowth.
It can be assumed that the unfavourable conditions in spruce forests can be alleviated by thinning. Also, mixture of pine and deciduous trees can transform the conditions more favourable in the spruce stands.
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