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:
“Strong to break dead things,
the young tree, drained of sap,
the old tree, ready to drop,
to lift from the rotting bed
of leaves, the old
crumbling pine tree stock.”
—Hilda Doolittle (1886–1961)
“Expediency of literature, reason of literature, lawfulness of writing down a thought, is questioned; much is to say on both sides, and, while the fight waxes hot, thou, dearest scholar, stick to thy foolish task, add a line every hour, and between whiles add a line.”
—Ralph Waldo Emerson (1803–1882)