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upper limit of tree growth in mountainous regions or in high latitudes, as in the Arctic. Its location depends largely on temperature but also on soil, drainage, and other factors. The mountain timberline always would be higher near the Equator than near the poles if it were not for the abundant rainfall in equatorial mountainous regions, which lowers the air temperatures. The timberline in the central Rockies and Sierra Nevadas is around 3,500 metres (11,500 feet), whereas in the Peruvian and Ecuadorian Andes it is between 3,000 and 3,300 metres (10,000 and 11,000 feet). In much of the central and southern Rockies there is a double timberline: the usual high timberline below which there is a belt of normal tree growth; and then a low timberline below which no trees grow because of low precipitation and high temperatures.