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60
I. PHYSICAL GEOGRAPHY.
5. FLORA.
Sweden, in consequence of its great extent from north to south, falls into
several different zones of vegetation distinguished by their climates. The
southernmost and south-western part belongs to the central European
region of deciduous forests; the main part belongs to the coniferous region
of the Northern Hemisphere; while the highest and northernmost parts
arc marked off by a vegetation that has characteristics in common with
the Arctic tundras. The whole country below the Alpine region has a
markedly forest climate. The rainy autumns and the snowy winters
provide the soil with a considerable supply of water, so that even during
the driest and warmest part of the period of vegetation the water
requirements can be satisfied. During the winters mild and moist winds mostly
prevail, so that the trees are not exposed to any very powerful
transpiration while the activity of the roots is crippled by the cold. Even in
the most- northerly parts of the forest-region the period of vegetation
has a warmish month with a mean temperature of -j- 11° C. Within
this region the forest is the natural plant-formation conditioned by the
climate. Other plant-communities that occur are conditioned either by
the peculiar nature of the soil (edaphic plant-formations such as mosses)
or by man’s interference with nature (cultivated formations, such as
ploughlands and meadows). Owing to differences in summer temperature,
and other but less significant differences in climate, the forests in the
southerly parts of the country have a quite different composition from
those in the northerly parts. We may distinguish a Beechwood region
which prevails in the southernmost and south-westerly part of the country,
a southerly and a northerly Coniferous region, and a Birchwood region
forming a transition to the Alps. The climate of the Alps is distinguished
by a character markedly unfavourable to trees. In the winter there
prevail cold and violent winds, which have a highly dessiccating effect on
the trees; and this is so much the more harmful to them because the water
they lose cannot be replaced from the frozen ground. The trees that
extend highest towards the Alps, therefore, appear in extremely deformed
shapes; and the Alpine vegetation proper, the Alpine heath, is destitute of
trees. The following five regions correspond to such considerable changes
in the character of the vegetation that the entire form of the landscape is
affected thereby: — viz., (1) the Alpine Region, (2) the Region of the
Birch Forest, (3) the Northern Region of Coniferous Forest, (4) the
Southern Region of Coniferous Forest, and (5) the Region of Beech
Forest.
The Alpine Region comprises the northernmost and highest part of the
country, and extends south as far as Northern Dalarne. Along the
Norwegian borders it forms a belt of varying breadth, severed or interrupted
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