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:
“I expect a time when, or rather an integrity by which, a man will get his coat as honestly and as perfectly fitting as a tree its bark. Now our garments are typical of our conformity to the ways of the world, i.e., of the devil, and to some extent react on us and poison us, like that shirt which Hercules put on.”
—Henry David Thoreau (1817–1862)
“I had lived over twenty years without the legal right to be alone one hour M to have the exclusive use of one foot of space M to receive an unopened letter, or to preserve a line of manuscript “from sharp and sly inspection.””
—Jane Grey Swisshelm (1815–1884)