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:
“a big picture of K. Marx with an axe,
“Where I cut off one it will never grow again.”
O Karl would it were true
I’d put my saw to work for you
& the wicked social tree would fall right down.”
—Gary Snyder (b. 1930)
“A line will take us hours maybe;
Yet if it does not seem a moment’s thought,
Our stitching and unstitching has been naught.”
—William Butler Yeats (1865–1939)