The tree line is the edge of the habitat at which trees are capable of growing. Beyond the tree line, they are unable to grow because of inappropriate environmental conditions (usually cold temperatures or lack of moisture). Some distinguish additionally a deeper timberline or forest line, where trees form a forest with a closed canopy.
At the tree line, tree growth is often very stunted, with the last trees forming low, densely matted bushes. If it is caused by wind, it is known as krummholz formation, from the German for 'twisted wood'.
The tree line, like many other natural lines (lake boundaries, for example), appears well-defined from a distance, but upon sufficiently close inspection, it is a gradual transition in most places. Trees grow shorter towards the inhospitable climate until they simply stop growing.
Famous quotes containing the words tree and/or line:
“A tree that can fill the span of a man’s arms
Grows from a downy tip;
A terrace nine stories high
Rises from hodfuls of earth;
A journey of a thousand miles
Starts from beneath one’s feet.”
—Lao-Tzu (6th century B.C.)
“The individual woman is required ... a thousand times a day to choose either to accept her appointed role and thereby rescue her good disposition out of the wreckage of her self-respect, or else follow an independent line of behavior and rescue her self-respect out of the wreckage of her good disposition.”
—Jeannette Rankin (1880–1973)