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 tree which moves some to tears of joy is in the eyes of others only a green thing that stands in the way. Some see nature all ridicule and deformity ... and some scarce see nature at all. But to the eyes of the man of imagination, nature is imagination itself.”
—William Blake (1757–1827)
“For almost seventy years the life insurance industry has been a smug sacred cow feeding the public a steady line of sacred bull.”
—Ralph Nader (b. 1934)