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The secret life of ancient trees

An ancient evergreen tree reveals its secret life to scientists, helping them decode climate history.

By Andy NelsonCorrespondent of the Christian Science Monitor / November 10, 2009

Researchers and a ranger examine core samples from a very old tree.

Andy Nelson

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Da Lat, Vietnam

A thousand years ago, the steep slopes of Vietnam’s southern highlands were cloaked by forests of towering pines and other trees. Tribesmen roamed the forests, hunting wild boar and deer under a lush canopy of laurels and oaks.

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In their quest for sustenance, they moved slowly through an understory of tangled bamboo and palms. Thick layers of moss and decaying leaves muffled their footsteps as they stalked their prey.

On the forest floor, the seed of a Fokienia hodginsii tree sprouted in the moist detritus. As it grew, a chronicle of each year of its life was locked into narrow bands inside its trunk – light for the beginning of a growing season and dark marking winter.

Now, a thousand years later, Vietnamese forest specialist Le Canh Nam and American tree ring scientist Brendan Buckley are hunting in the forest. But their quarry isn’t wild boar or deer. It’s the tree that grew from the Fokienia hodginsii seed and has survived for a millennium, growing into an ancient giant.

Like the hunters of the past, Mr. Nam walks deliberately through prickly stands of rattan palms and over downed trees in what is now Bidoup-Nui Ba National Park near Da Lat, Vietnam.

Nam’s quest began two years ago when he was asked by Dr. Buckley to find ancient Fokienia hodginsii trees from which he and a team of scientists could extract tree rings to help with climate studies.

Buckley and his colleagues have spent the past five years working with collaborators in more than a dozen countries to reconstruct information about historical monsoons from tree rings. Such data is useful for climate modelers, who want to find out how global warming might affect monsoon rainfall.

The models that predict rising temperatures are “very iffy” about precipitation patterns, says Edward Cook, director of Columbia University’s Lamont-Doherty Earth Observatory (LDEO) Tree- Ring Laboratory. That puts a premium on figuring out how much it rains from year to year in Asia’s densely populated river deltas. Tree rings help scientists understand past climate variations.

Nam spent a week in the forest searching for big trees. Now he is guiding the group back to a promising site.

“A tree that is beautiful to me is probably ugly to most people, says Buckley. “Mine are twisted and have been through hell on a weathered ridge or dry slope. Those are the trees I’m interested in.”

Buckley is considered the foremost tree-ring scientist (dendrochronologist) working in Southeast Asia and is a research scientist at LDEO’s Tree-Ring Laboratory. Nam consults his map, a global positioning system, and a compass, and relies on an intuitive sense of direction developed through years in the forest.

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