timberline

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timberline,

elevation above which trees cannot grow. Its location is influenced by the various factors that determine temperature, including latitude, prevailing wind directions, and exposure to sunlight. In general, the timberline is highest in the tropics and descends in elevation toward the polar regions; in the north it intersects the land surface approximately at the Arctic Circle. For example, the timberline is at about 2,500 ft (750 m) on Denali (Mt. McKinley), Alaska; 6,500 ft (1,950 m) on Mt. Shasta, Calif.; and 11,500 ft (3,450 m) in the San Francisco Mts., Ariz. These figures represent elevations on the sunny side of the mountains; the timberline is lower on the shaded sides. The timberline is roughly marked by the location of the 50°F; (10°C;) isotherm (see isoplethisopleth
, line drawn on a map through all points of equal value of some measurable quantity. In many meteorologic, oceanographic, or geologic studies some physical or chemical property is examined that varies from place to place on a map.
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) during the warmest month.

timberline

[′tim·bər‚līn]
(ecology)
The elevation or latitudinal limits for arboreal growth. Also known as tree line.
References in periodicals archive ?
Polylepis trees are found high above the normal timber line (up to 15,748 ft [4,800 m] in the case of P.
The precise altitude of the timber line on a mountain depends on the geographical location and climate of each massif.
Often, at the timber line, the forest is stunted and more open and then gradually dies out.
They are normally located above the timber line and are often in sites with little vegetation, sometimes almost deserts, and so the water is relatively poor in humic materials, distinguishing them from the lowland lakes of northern Europe and Canada, with which they otherwise have much in common.
136 The remarkable tuft-rosette of leaves of the frailejon Espeletia pycnophylla is a typical feature of the plant landscape of the higher levels of the wet Andes, where these plants cover immense areas above the timber line. The tuft-rosette of hairy leaves is born at the end of a thick stem, and the different species (in this case Espeletia pycnophylla) form a very unusual plant landscape.
138 The timber line and the upper limit of vascular plants is at a greater elevation in tropical regions and descends with increasing latitudes.
This was followed by a section headed by: "The Timber Line has the following objectives with respect to this project:"
End of pine forest clearly marks the mountain's, 7,000-foot timber line
Photo: On the mountain, day-hikers rest above timber line; ice axes, advised for summit climb, aren't needed on low, snowless slopes

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