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:
“But when the bowels of the earth were sought,
And men her golden entrails did espy,
This mischief then into the world was brought,
This framed the mint which coined our misery.
...
And thus began th’exordium of our woes,
The fatal dumb-show of our misery;
Here sprang the tree on which our mischief grows,
The dreary subject of world’s tragedy.”
—Michael Drayton (1563–1631)
“Too many girls follow the line of least resistance—but a good line is hard to resist.”
—Raoul Walsh, U.S. screenwriter. Frisco Doll (Mae West)