Bristlecone Pines: The Oldest Living Tree

On our recent trip to California, my wife and I drove up to Schulman Grove in the White Mountains to see the ancient bristlecone pines. Specimens of the Great Basin bristlecone pine (Pinus longaeva), are the oldest living trees in the world. These bristlecone pines have needles that grow in bundles of five. The needles are short for a pine, only about one inch long and spread along the branch like a bottle brush. However, these short needles live a long time, lasting up to 43 years. The cones are about three inches long. The growth form is often contorted and gnarled. Old trees have colorful, exposed wood that has lost its bark. Great Basin bristlecone pines grow at elevations over 10,000 feet in the White Mountains of California, and to the east in the mountains of Nevada and Utah. 

In 1953, Edmund Schulman discovered the world's first known 4000-year-old tree in the grove of bristlecone pines now called Schulman Grove. He used an increment borer to get samples of the growth rings of many of the bristlecone pines in the area and discovered one that was over 4700 years old. The oldest known living tree is another bristlecone pine that is over 5000 years old (5060 years old in 2012). It is growing at an undisclosed location, about 12 miles north of Schulman Grove.

Schulman Grove is located 24 miles from Big Pine, California. The road to get there is paved, but steep and winding. There is parking at the Ancient Bristlecone Pine Forest Visitor Center, where you can hike three trails at Schulman Grove. There is no water to be had in lake, stream, spring, or well, which tells you something about the arid nature of the White Mountains, and should suggest something about the nature of the bathroom facilities located near the Visitor Center. I hiked around the mile long Discovery Trail loop to get the photos shown here.

Tree-ring dating
It's easy to determine the age of a tree by counting the annual growth rings after it has been cut down. A less destructive way is to use an increment borer. This device is a long hollow drill bit that can extract a thin cross section of a tree, which enables you to count the tree rings. Also, since the rings are wider in wet years, you can determine variable weather patterns throughout the history of a tree. Furthermore, this variability forms patterns that researchers can recognize in different core samples. By comparing cores from living trees with cores from dead trees and wood fragments, researchers can extend their knowledge of weather patterns back for thousands of years. We now have a continuous record of bristlecone pine tree rings going back over 11,000 years. Also, tree rings in the wood at archaeological sites enable scientists to determine the age of the wood.

Since the tree rings provide an accurate count of the years, this research has enabled scientists to calibrate the readings from radiocarbon dating, giving archaeologists all over the world more accurate data on the age of artifacts.