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:
“The great pines stand at a considerable distance from each other. Each tree grows alone, murmurs alone, thinks alone. They do not intrude upon each other. The Navajos are not much in the habit of giving or of asking help. Their language is not a communicative one, and they never attempt an interchange of personality in speech. Over their forests there is the same inexorable reserve. Each tree has its exalted power to bear.”
—Willa Cather (1873–1947)
“What, will the line stretch out to the crack of doom?”
—William Shakespeare (1564–1616)