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:
“Here is a hero who did nothing but shake the tree as soon as the fruit was ripe. Does this seem to be too small a thing to you? Then take a good look at the tree he shook.”
—Friedrich Nietzsche (1844–1900)
“We are apt to say that a foreign policy is successful only when the country, or at any rate the governing class, is united behind it. In reality, every line of policy is repudiated by a section, often by an influential section, of the country concerned. A foreign minister who waited until everyone agreed with him would have no foreign policy at all.”
—A.J.P. (Alan John Percivale)