World's Largest Tree Is Younger Than Once Thought
UniSci - Daily University Science News, http://unisci.com/
December 8, 2000
The world's largest tree, a giant sequoia growing in California's Sequoia National Park, just keeps getting younger. The massive conifer, named General Sherman in 1879 by admirers of the Civil War general, may be little more than 2,000 years old, according to a U.S. Geological Survey study.
New age estimates for this and several other famous giant sequoias -- including the General Grant tree, known as the "Nation's Christmas Tree" -- are found in an article by research ecologist Nate Stephenson of the USGS Western Ecological Research Center in the botanical journal MadroZo.
The General Sherman tree measures 275 feet tall and 30 feet across at the base. Early estimates placed the tree's age at 5,000 to 6,000 years, and later at 2,500 to 3,500 years, as techniques for estimating sequoia ages have become more accurate.
"We now think the tree is even younger, perhaps only 2,100 to 2,200 years old," said Stephenson. "The Sherman tree's extreme bulk, more than ten times larger than a blue whale, has long led people to believe that its age was also extreme. The relative youth of the world's largest tree comes as something of a surprise."
Extremely large trees are not necessarily the oldest, said Stephenson. Tree rings in cut sequoia stumps show that sequoias much smaller than the Sherman tree have reached ages of more than 3,200 years.
"The Sherman tree isn't so large because it's exceptionally old, but because it's growing so fast," Stephenson said. "Each year it adds enough wood to make a tree one foot in diameter and more than 100 feet tall."
The new age estimate relies on tree-ring measurements from pencil-thin, foot-long cores of wood removed from near the base of the Sherman tree, and mathematical formulas based on measurements from hundreds of sequoia stumps. The age-estimate technique was developed as part of a study by Stephenson and his colleagues to determine the effects of past changes in climate and fire frequency on giant sequoias.
"The new Sherman tree age-estimate of about 2,150 years could still be off by centuries," Stephenson concedes. "Getting a precise age measurement would require boring a hole several inches wide all the way to the center of the tree."
"We don't want to risk harming this special tree by removing such a large core," said Bill Tweed, acting superintendent of Sequoia and Kings Canyon National Parks.
The new age-estimates of other famous sequoias likewise suggest more youthful trees. Stephenson estimates that the General Grant tree is only about 1,650 years old, and the popular Grizzly Giant tree of Yosemite National Park is only about 1,800 years old.
"Most of the largest sequoias are really just middle-aged," said Stephenson. "But they're still growing like teenagers -- at a fast and furious rate."