Tree line

The tree line or timberline is the edge of the habitat at which trees are capable of growing. Beyond the tree line, they are unable to grow due to inappropriate environmental conditions.

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. Trees grow shorter towards the inhospitable climate until they simply stop growing.