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tree line

Therefore the tree line has now been accepted as the southern boundary of the Arctic .

The tree line is not, however, a clear-cut boundary which sharply separates dense stands of forest from completely treeless barren grounds .

When this limit is passed the trees generally grow shorter, but the forest continues as islands or scattered trees, sometimes following watercourses far into the otherwise treeless country .

As a result of wind and snow blast, the trees farther north eventually become dwarfed and stunted, and finally disappear completely. Near the limit of existence trees can grow only under especially favorable conditions, and are therefore restricted to valleys of rivers, south-facing and well-drained slopes, sheltered depressions or calcareous soil .