The ancient Bristlecone pines of the southwestern United States are the oldest living trees in the world, with some individual trees nearly 5,000 years old. How is it that these trees are able to survive for so long?
Characteristics of the Bristlecone Pine Tree
In part, the harsh environment in which they live contributes to the Bristlecones' longevity. They are found only at high elevations, usually between 11,000 and 12,000 feet. They grow in outcroppings of dolomite limestone, a light colored alkaline soil that holds more moisture and reflects light better than the predominant sandstone and granite. The characteristics of the dolomite soil help to keep the roots cool and moist. Very few insects live in this environment, reducing the threat to the trees. In addition, their wood is dense and resinous, which serves to protect them from invading insects, fungi and bacteria.
Bristlecones are slow growing trees, rarely reaching 60 feet in height, and usually much shorter. Many of the oldest trees are squat, broad and gnarled. Bristlecones retain their needles for up to 30 years, which conserves energy since they seldom have to produce new foliage.
Dendrochronology, or Tree-Ring Dating
Scientists determine the age of trees by a method called dendrochronology. Trees form a series of concentric rings as they grow, with one ring correlating to each year of the tree's life. By counting the rings, researchers can accurately determine the age of a tree. To avoid cutting down a living tree, a long, thin core sample can be taken using a special drill. Using this method, scientists have found that many of the Bristlecone pines are between 3,000 and 4,000 years old. The oldest known Bristlecone pine, named Methuseleh, growing in the White Mountains of California, was found to be 4,723 years old in 1957.
Even after a Bristlecone dies, it remains standing for centuries. Due to the cold, dry climate in which these trees grow, fallen wood does not decay and remains intact for thousands of years. By piecing together overlapping ring patterns of living and dead trees, scientists have been able to construct a continuous record dating back nearly 9,000 years.
Distribution of Bristlecone Pines
Bristlecone pines are found only in six western states. Originally thought to be all the same species, in 1970 it was found that there were enough differences between the western and eastern varieties to categorize them as two different but closely related species. The western species, Pinus longaeva, lives in California, Nevada and Utah. The eastern species, Pinus aristata, is found in Colorado, Arizona and New Mexico. The oldest trees, including Methuseleh, are located in the White Mountains of California.
Source:
Miller, Leonard. "The Ancient Bristlecone Pine." Accessed August 16, 2010.
Terrie Schultz - Terrie Schultz holds a BS in Biochemistry and an MA in Cell and Molecular Biology. She worked for many years in the biomedical field in ...
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