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:
“Happy are those who find wisdom, and those who get understanding, for her income is better than silver, and her revenue better than gold. She is more precious than jewels, and nothing you desire can compare with her. Long life is in her right hand; in her left hand are riches and honor. Her ways are ways of pleasantness, and all her paths are peace. She is a tree of life to those who lay hold of her; those who hold her fast are called happy.”
—Bible: Hebrew, Proverbs 3:13-18.
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—Fred G. Gosman (20th century)