Saturday, August 30, 2003

FEAR FOR THE AGED

600-year-old fir dies in Aspen fire, but forest's oldest survives

A UA researcher finds charred, dead wood in the Catalinas where ancient pines once stood proudly since the 14th century.

LARRY COPENHAVER

Tucson Citizen

It was a long trudge through the burned forest, especially in the face of tropical storm remnants that shrouded much of the Santa Catalina Mountains in heavy fog and dumped rain across the area Wednesday.

Despite the tempest, Rex Adams, a scientist with the Laboratory of Tree-Ring Research at the University of Arizona, pushed on through the ghost forest to find the answer to several questions.

The most pressing was: Did this summer's Aspen fire wipe out the oldest known living trees in southern Arizona?

The fire ravaged 85,000 acres in the Coronado National Forest in June and July. One of the areas hit hardest was Reef of Rocks, the site near where scientists had documented the existence of four living ancient Douglas fir trees five years ago.

The only way Adams could learn the trees' fate was to scale steep slopes covered with ash and find the craggy outcropping at 8,500 feet.

There, reality hit.

"They're gone. They're gone, but at least the oldest one made it," he said.

Known as tree Number 14, the oldest of the four was dated by UA tree-ring scientists to 1320. The other three germinated in the 1380s and 1390s.

That means Number 14 was alive 172 years before Christopher Columbus landed in the Americas, 244 years before Michelangelo died and 456 years before the American Revolution began.

Adams had been optimistic about the trees' survival. After all, scientists say the trees managed to live so long because they were in a hostile environment where few other trees or shrubs managed to thrive.

And without other significant wood, fire posed less of a threat than it did in thick stands of fuel.

Though two of the trees were definitely dead, Adams said it was too early to tell whether the fourth would make it.

"It's a great loss," Adams said.

The Aspen fire destroyed much of the vegetation on nearly 133 square miles of wilderness and burned more than 300 homes and business on Mount Lemmon, mostly in the mountaintop community of Summerhaven.

The nearly seven centuries of historic data the dead trees contained likely cannot be replaced.

Scientists may try to salvage the vast data in the tree rings by cutting a slab from the now-dead wood and taking it to the laboratory for analysis.

Tree-ring studies can reveal a tremendous historic record.

The width of the rings and the density of the cellulose tell a story, Adams explained. And modern isotope analysis can yield data on water sources, even the origin of storms that provided nourishing rain to the trees.

Scientists use stable isotopes ratios, or ratios of non-radioactive forms of such elements as oxygen, to help reconstruct environmental history, he said.

Also hidden in the rings is a record of environmental hazards, he said. Some scientists even believe the rings might eventually help document environmental changes, such as pollution, that could cause cancer or other dreaded diseases, he explained.

For decades, the oldest known trees living in southern Arizona were Douglas firs in the Santa Rita Mountains, south of Tucson.

The oldest known living tree in the Catalinas was a ponderosa pine with an inner date of 1412. That tree, on Green Mountain, died during the drought of 1989, Adams said.

Firs, including a living 1414 tree, were discovered in the 1940s by a distinguished UA tree-ring scientist, Edmund Schulman.

Tree-Ring Laboratory graduate student Ed Wright found the ancient Reef of Rocks Douglas fir on May 31, 1998.

The tree Adams hiked to Wednesday is considered the granddaddy of them all. It began life at the height of the Hohokam Classic Period, when people in central and southern Arizona built ceremonial platform mounds, hunted animals and farmed with the largest prehistoric system of irrigation canals north of Peru.

Wright found that tree on one of his weekend scouting trips to the very old living trees and remnant wood Schulman discovered in the 1940s.

The student-scientist collected pencil-thin core samples, believed not to damage trees, from the live trees as well as samples from dead wood in the areas.

Beyond southern Arizona, the oldest living trees in Arizona are bristlecone pines on the San Francisco Peaks around Flagstaff. Several of them date to the 1200s.

Matthew Salzer, adjunct assistant professor with UA's tree-ring lab, found the oldest living bristlecone in that area, a tree that began growing before 658.

Also killed by the Aspen fire was a saguaro cactus said to be growing at the highest elevation ever recorded for such a plant, said Heidi Schewel, a spokeswoman for Coronado National Forest.

Generally, saguaros are found mainly in the Sonoran Desert from sea level to 4,000 feet.

The high-elevation saguaro was at about the 5,000-foot level, a mile from the old prison camp, she said. All that is left is charred remnants of its inner wood structure.

Wednesday, Adams also saw firsthand that the Aspen fire took a toll on a stand of about 1,000 corkbark fir.

"We lost half of them," Adams said.

A small number of the trees, which are unusual in this part of the country, are on Mount Lemmon, near the ski area.

"The (corkbark) fir is very susceptible to surface fire," said Tom W. Swetnam, director of the Tree-Ring Laboratory.

That might account for the dramatic die-off here, despite the fact that the fire burned through the area mainly on the ground.

Corkbark fir trees - so-called because the tree's smooth bark is soft to the touch - have bluish-green to silvery-colored needles. Though there are few in southern Arizona, they can be found at higher elevations in some mountain ranges.

"We think the stand will survive, and it will continue to be a part of the mountain," Swetnam said.

The biggest fear is that another fire could take what's left. He worries that the dead trees from the Aspen fire most likely will add fuel to the fire hazard.

"There is still a heck of lot of forest up there, and there is still plenty to burn," he said.