What is "tree line"

n. 1 A division in altitude above which trees tend not to grow on mountains. 2 A division in latitude where latitudes higher than that do not tend to grow trees (this line is not a constant latitude)

n. line marking the upper limit of tree growth in mountains or northern latitudes [syn: timber line, timberline]

The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and in frigid environments. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures or lack of moisture). The tree line should not be confused with a lower timberline or forest line, which is the line where trees form a forest with a closed canopy.

At the tree line, tree growth is often sparse and stunted, with the last trees forming densely matted bushes, known as krummholz (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.