December 22, 2009

Strange BiologyTree With an Ancient Past

Bristlecone pines, such as those growing in the White Mountains, are extremely long-lived organisms. (Photo credit: Stephen Saks Photography/Alamy)

Talk about tenacity—not only are bristlecone pines among the oldest organisms alive, but they also survive in rather harsh conditions. These long-lived organisms have a number of interesting adaptations that allow them to survive over long periods of time in what many other organisms would consider to be rather hostile conditions.

Natural History

Two species of bristlecone pine live in the United States: Pinus longaeva and Pinus aristata. Though originally considered to be just one species (P. longaeva), further investigation by scientist Dr. Dana K. Bailey in the 1960s indicated that genetic and structural differences within the species were significant enough to warrant dividing the bristlecone pine into two separate species. P. longaeva, commonly called the Great Basin bristlecone pine, are found in California, Nevada, and Utah. P. aristata, also known as Rocky Mountain bristlecone pine, has populations in Colorado and Arizona. The most long-lived bristlecone pines belong to the P. longaeva species, and the oldest known bristlecone pine is found in California's White Mountains.

Bristlecone pines get their name from the long prickly bristle found at the end of each scale on the tree's cones. These pines can be identified from other conifers by their needles, which are one inch in length and grow in bunches of five. The needles completely surround the tree's branches. Like other conifers, bristlecone pines reproduce through their cones. The tree's cones start out deep purple in color and as they mature over a two-year period they turn brown.

Immature cones are purple, as the cones mature they turn brown in color. (Photo credit: Dennis Flaherty/Photo Researchers, Inc.)

Habitat

The most studied population of ancient bristlecone pines is found in the White Mountains in the Inyo National Forest. Among the population of bristlecone pines that live here is the famed Methuselah tree, which has been dated (using dendrochronology techniques) to an age of over 4600 years old.

The Methuselah tree and other bristlecone pines found in the White Mountains live in particularly harsh conditions. First, many are found at high elevations (up to 3470 meters (or over 11,000 feet). At such high elevations, little vegetation exists. The oldest known bristlecone pines grow here on a rocky alkaline soil made up of dolomite, a type of limestone. Because little else is able to survive on such alkaline soil, bristlecone pines are able to survive here relatively competitor-free. Another factor that makes life more difficult for bristlecone pines is the climatic conditions at high elevations which are particularly cold and dry. Such harsh conditions drastically limit the bristlecone pine's growth. Because these trees grow at such a slow rate, their wood is particularly dense. This dense and highly-resinous wood makes it basically impenetrable to attacks by bacteria, fungus, or insects. With such dense wood and little other vegetation in the area, these trees are also protected from fire events.

Contribution to Science

In addition to their other fascinating attributes, bristlecone pines have even contributed to science. In the 1960s, scientists discovered that the radiocarbon dating process was flawed. Given that scientists could precisely determine a tree's age by counting its rings, scientists were able to calibrate the radiocarbon dating method by comparing a tree's known age with the amount of carbon-14 in samples from the same tree. In doing so, the scientists found that radiocarbon dating routinely underestimated a sample's age. With the help of the bristlecone pine samples, the scientists were able to calculate a calibration factor to account for this underestimation and thus correct the dating process.

More to Explore

• Inyo National Forest: Bristlecone Pine Forest
• Bristlecone Pine
• Methuselah Tree: A Tree's Secret to Living Long
• Identifying Bristlecone Pines

Last updated December 22, 2009 | Comments (3) | Permalink | Strange Biology