The importance of fire for the regeneration of the forests has never been so topical as in our days, when increasing use is made of controlled burning in the interests of forestry. In 1955 about 40,000 hectares of forest land, belonging to the Forest Service and the companies, were control-burned. These forests comprise together about 9,700,000 hectares, i.e. almost the half of the total forest area in Sweden... The fire has an indirectly favourable influence also in the long run by favouring the entry of birch and aspen as pioneer trees into the burnt areas. The leaves produce every year a new contribution of litter upon he soil, the temperature of which rises below the leafless trees in the spring. This produces an improvement of the humus conditions which lasts for many years (ARNBORG 1949 a, 1951, SJÖRS 1954, SIRÉN 1955, UGGLA 1957 b, etc.). But the effects of the fire are not always as favourable as after a feeble forest fire or a controlled burning. An uncontrolled forest fire upon meagre soil can produce devastating effects, especially if the humus cover has been burnt. Upon such soils the activating effects of the fire soon disappear, and since also the addition of litter is very inconsiderable, a degeneration of the woodland often results.