Our Window on Nature

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The Oldest Living Tree is a Bush

Filed under: Plants — Lowell Christie -- May 6, 2007 @ 1:05 pm

CreasoteWhen we were kids in school, it was common knowledge that California’s redwoods were both the world’s oldest and its tallest trees, and that the earliest of them sprouted at about the time Jesus Christ was born. Then some wise guy discovered bristlecone pines of twice that age growing atop the barren peaks of California’s White Mountains, and we had to revise our thinking about longevity.

Now another researcher from the Golden State has thrown us a curve. Dr. Frank C. Vasek of the University of California at Riverside claims to have found a new “oldest living organism on earth” growing in the Mojave desert — only this time, it’s a bush.

Travel through the Chihuahuan, Sonoran, and Mojave deserts from Big Bend National Park to Joshua Tree National Monument, and the most common form of vegetation that you’ll find outside your window is the creosote. This bush thrives at below sea level in Death Valley. It grows where nothing else will, in the desiccated plains surrounding Yuma, where there is a miserly three inches of rainfall a year. Creosote even tolerates being buried by sand dunes, as long as it can grow fast enough to keep a few branches poking up through the sand. In short, this plant is a survivor.

It was at least 11,700 years ago that the American Southwest turned into a desert as we know it. The last Ice Age ended, the climate warmed and dried, and conditions were ready for new forms of vegetation. Creosote was the first plant to inhabit the desert terrain, and since the oldest creosote is estimated to be 11,700 years of age, we must have had deserts around for at least that long.

(That makes the oldest living creosote twice the age of the oldest bristlecone. Sound familiar?)

This new plant species was no stranger to deserts, having migrated north from the arid lands of Argentina, gradually populating the terrain as it was vacated by trees and shrubs that were more dependent on plentiful rains. With its ability to become dormant during the drought season and its technique for extracting every droplet of moisture from the soil, creosote survived in places where nothing else could.

It wasn’t the success of creosote as a desert survivor that triggered the interest of Dr. Vasek, however; it was the plant’s growth pattern. He noticed that creosote bushes typically grow in elliptical colonies, so that a ring of bushes surrounds an area of dead wood and bare sand. Since he already knew that creosote reproduces by sending out shoots, Vasek guessed that these bushes were, in fact, all part of the same plant, descended from an ancestor that had once lived in the center of the ring.

The facts get a little sticky here. If the ancestor who once set things in motion is gone, and the plant’s age must be extrapolated from the average growth rate of the ring, based upon so many inches of outward movement every century, then even if the plants we see today are genetic clones, which they are, are they still part of the same plant? Dr. Vasek insists that they are.

For even though the individual stems and leaves that we see today are a mere two or three hundred years old, the patch of creosote measuring 70 feet by 25 feet and known affectionately as King Clone first started growing 11,700 years ago. The U.C. botanist says that this makes King Clone the world’s oldest plant.

Dr. Vasek compares the living fringes of King Clone with the outer layer of living bark on a redwood tree. The inside of the redwood may have long since rotted away or been burned out (trees that tall are natural lightning rods), but as long as the outer growth ring remains intact, the tree lives. It’s the same thing with the creosote ring, he says. The creosote bush starts with a sprouting seed. As it grows, the bush gradually spreads outward, with the inside dying and rotting away and the growth portion spreading over an increasingly large area.

It seems odd that, since this oldest known creosote bush is growing in the Mojave Desert, the earliest North American creosote seed should have sprouted in the Chihuahuan Desert in Texas, rather than in California. But apparently that’s what happened. From Texas the bush made its way west across the Sonoran Desert, being fruitful and multiplying along the way to California and the Mojave Desert.

There, where climatic conditions are the harshest and, therefore, the most agreeable to creosote survival, stand the most ancient living specimens.

Dr. Vasek set out to convince the Nature Conservancy that King Clone, the most venerable member of this ancient population, merits protection. Right now the bush is in a remote area, but at the rate that the Mojave Desert is losing out to housing developments, dune buggies, and dirt bikes, that security won’t last long. Present plans call for the Conservancy to buy the property, and ultimately transfer it to the university for management and research. The folks there want to know a lot more about the world’s oldest living plant.

So the next time you travel to the desert, don’t overlook the lowly creosote bush. Those straggly branches full of puffy yellow blossoms may actually be hundreds of years old. And although they don’t look as impressive as Joshua trees and saguaro cacti, when it comes to longevity, that scrawny creosote carries one key to perpetual youth.

FMC286


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