This article would be most useful as a source for a student research project on __________.
A. Universally accepted naming conventions for various tree species
B. Comparing and contrasting giant sequoias and coastal redwoods
C. Examples of living fossils that are of interest to scientists today
D. How increasing absorption of carbon dioxide helps the environment

This is the article:
Giants of California
Life Science Studies: Energy and Relationships in Ecosystems



FRESNO, California (Achieve3000, June 21, 2013). Conjure up an image of a towering tree in your neighborhood, and consider for a moment how it compares with the houses and buildings on your street. Now imagine a tree that is 26 stories high and thick enough that if it were hollow, you could comfortably camp inside. This isn't a fictive tree dreamed up by mythmakers and storytellers. Gargantuan trees like this exist—they're called giant sequoias, and they're native to the Sierra Nevada Mountains of California.

Giant sequoias are so imposing that the biggest ones have names, and they are ranked by size—one impressive tree, the General Sherman, is the largest of all sequoias, and the largest (though not the tallest) tree on the planet. According to the latest data, the enormous tree is 274.9 feet (83.8 meters) high, 102.6 feet (31.3 meters) in circumference, and 36.5 feet (11.1 meters) in diameter at the base—that's about half the width of a high school gym. And like many of its kindred giant sequoias, the General Sherman is still growing.

Clearly, a tree this large must be very old, and scientists estimate that the General Sherman is indeed about 2,500 years old, which means it was a sapling when, across a continent and an ocean, Ancient Greece was at its apogee.

The General Sherman is joined in its grandeur by a giant sequoia called The President (the tree's moniker is in honor of U.S. President Warren G. Harding), which measures some 93 feet (28 meters) in circumference, and like the General Sherman, the 3,240-year-old tree grows in Sequoia National Park. Scientists are fascinated with The President, which after comprehensive measurements, has been deemed the second-largest tree in the world—it is currently about 15 percent larger than the third-largest tree, the General Grant.

"I consider [The President] to be the greatest tree in all of the mountains of the world," said Stephen Sillett, a researcher whose team from Humboldt State University is studying the giant trees of California.

Sillett and his team are the scientists who discovered that The President deserved second billing—not third—in size rankings. After taking 15 half-centimeter-wide core samples of The President to determine its growth rate, they discovered that the tree's growth was stunted in the abnormally cold year of 1580, when temperatures in the Sierra Nevada hovered near freezing, even in the summer, and the trees remained dormant. They also learned that ancient trees like The President don't slow down with age—they actually speed up their growth processes as they get older. The President adds about one cubic meter of wood a year during its short six-month growing season, making it one of the fastest-growing trees in the world. It's hard to fathom how much larger a giant like The President could get in just a few hundred more years.

Sillett and his team aren't just in the business of gawking at humongous trees, though, and through their research they've determined that The President holds another distinction that could make a difference in our future—its 2 billion leaves are thought to be the most of any tree on the planet. All of those leaves make it one of the most efficient trees at absorbing carbon dioxide, which scientists believe is one cause of deleterious climate change.

"We're not going to save the world with any one strategy, but part of the value of these great trees is this contribution, and we're trying to get a handle on the math behind that," Sillett explained.

Giant sequoias grow so big and for so long because their wood is resistant to the pests and diseases that dwarf the lifespan of other species of trees, many of which live only a few hundred years, and their thick bark makes sequoias impervious to fast-moving fires.

It's that resiliency that makes sequoias and their even taller coastal redwood cousin worthy of intensive protections, Sillett said, adding that he doesn't care that The President hasn't caught up to the giant among giants, the General Sherman. For him, it's not a contest.

"They're all superlative in their own way," Sillett affirmed.