Blighted icon: Volunteers aim to revive chestnut
- Article by: ALLEN G. BREED
- Associated Press
- December 8, 2012 - 9:04 AM
WEAVERVILLE, N.C. - Jim Hurst has doted on his trees, arranged in three "families" on a bluff high above the rushing French Broad River.
He installed a drip irrigation system to help rejuvenate this former hayfield's powdery, depleted soil. To protect against browsing deer, he girded the delicate sprouts in plastic sleeving and wire mesh. In the four years since planting the fuzzy, deep-brown nuts, he nursed the seedlings — through back-to-back droughts, a killing frost, even an infestation of 17-year locust — applying herbicides and mowing between the rows to knock down anything that might compete.
Then, on a hot day this past June, Hurst moved methodically along the steep hillside, a petri dish in his left hand, and infected the young saplings with the fungus that will almost certainly kill them.
It wasn't malice, but science — and hope — that led him to take such an action against these special trees.
"My mother's family never stopped grieving for the (American) chestnuts," the 51-year-old software engineer and father of two said as a stiff breeze rustled through the 110 or so surviving trees, many already bearing angry, orange-black cankers around the inoculation sites.
"Her generation viewed chestnuts as paradise lost."
Hurst hopes the trees on his hillside farm — part of a vast experiment in forest plots where this "linchpin" species thrived before the onslaught of an imported parasite — might hold the key to regaining that Eden.
The American chestnut once towered over everything else in the forest. It was called the "redwood of the East." Dominating the landscape from Georgia to Maine, Castanea dentata provided the raw materials that fueled the young nation's westward expansion, and inspired the words of Henry Wadsworth Longfellow and Henry David Thoreau.
Then, the blight struck. By the 1950s, this mightiest of trees was all but extinct — "gone down like a slaughtered army," in the words of naturalist Donald Culross Peattie.
Now, after 30 years of breeding and crossbreeding, The American Chestnut Foundation believes it has developed a potentially blight-resistant tree, dubbed hopefully, the "Restoration Chestnut 1.0."
At a national summit in Asheville in mid-October, the group's board adopted a master plan for planting millions of trees in the 19 states of the chestnut's original range.
This year, volunteers in state chapters established seed orchards that will soon begin producing regionally adapted nuts for transplanting into the wild. But as those who attended the recent summit heard, much hard work remains — and much uncertainty.
The restoration tree is being introduced onto a physical and economic landscape that has long since learned to do without the once-indispensable American chestnut. Will it crowd out other trees and plants that we have come to value in the past century? How do you convince landowners and government agencies that it's worth the money and effort?
And there are those who will question the wisdom of trying to bring back something that could not survive on its own or, worse yet, "engineering" a replacement that can. But Hurst and the others at the summit are confident there is no obstacle they can't overcome in the effort to restore the East's "cathedral forests."
"I think that's something worth fighting for," he said. "To fix something that's broken."
In the spring of 1540, Spanish conquistador Hernando de Soto's quest for silver and gold brought him to the Blue Ridge Mountains, in what is now western North Carolina. A survivor of the expedition would later record: "Where there be mountains, there be chestnuts."
More than 500 years later, Peattie conjured that virgin landscape in full flower: "the great forest below waving with creamy white Chestnut blossoms in the crowns of the ancient trees, so that it looked like a sea with white combers plowing across its surface."
With trunks measuring 10, 12, even 17 feet in diameter, the trees' branches soared up to 120 feet above the forest floor.
Along the continent's Appalachian spine, chestnuts covered some 200 million acres — comprising fully a quarter and, in some places as much as two-thirds, of the upland forest. It is difficult to overstate the tree's importance.
Settlers built cabins, rail fences and barns out of its light, strong, even-grained wood. They hunted deer, turkeys and squirrels made fat on its mast — and themselves feasted on the sweet, starchy nuts.
Thoreau wrote lovingly of going "a-chestnutting" in the New England woods. In an 1857 journal entry contemplating the chestnut's spiny bur, he rhapsodized on the wonderful care with which nature "has secluded and defended these nuts, as if they were her most precious fruits, while diamonds are left to take care of themselves."
Tannins from the tree's bark cured the leather for belts that powered machines that drove the Industrial Revolution. The chestnut's naturally rot-resistant wood supplied most of the railroad ties and telegraph poles that knitted together the rapidly expanding United States.
"At last when the tree can no longer serve us in any other way," forest economist P.L. Buttrick observed, "it forms the basic wood onto which oak and other woods are veneered to make our coffins."
But by the time he wrote those words in 1915, a death knell had already sounded for the American chestnut.
It is unclear exactly when or how the blight arrived here, though most agree it came on chestnut trees imported from China or Japan. The fungus — Cryphonectria parasitica — was first identified in 1904 by employees of the New York Zoological Park and was soon detected in chestnuts as far south as Virginia.
Entering through wounds in the bark, the fungus threads its way through the straw-like vessels that carry water and nutrients from the ground to the tree's crown. As the tree responds to plug these holes, the blight works its way around the trunk "until it is completely girdled," William A. Murrill, the botanical garden's assistant curator, wrote in 1906.
"The tree essentially commits suicide," said geoscientist Frederick Paillet, an emeritus professor at the University of Arkansas who has studied chestnuts for nearly a half century.
Carried by insects and on the wind, the blight cut through the forests like an invisible scythe. By the mid-20th century, it had spread throughout the entire range — killing an estimated 4 billion trees in one of the worst ecological calamities in U.S. history.
But the American chestnut has not disappeared altogether. Millions of seedlings still sprout each year from old stumps or long-buried nuts. Most reach just a few feet in height before the blight — which persists in the soil and on the bark of surrounding trees — ultimately finds and kills them.
Occasionally, someone will stumble across a tree that has managed to live long enough to flower. Such specimens are referred to as LSA's — "large surviving Americans."
Last year, Traylor Renfro was clearing trails at his mountaintop retreat in Grassy Creek, near the Virginia border, when something pricked his finger. At first, he thought he'd been stung.
"And then when I looked at it, I realized that it was a bur," he said.
He was aware of the blight, and so his prime suspect was one of the bushlike chinquapins scattered about. His search for more burs led him to a nearby tree, its long, feather-like leaves edged with teeth that resemble breaking ocean waves.
It was an American chestnut — about 37 inches around and at least 50 feet tall.
Nearby, Renfro found several young chestnuts that had sprouted from a desiccated, diseased stump. Examining the larger tree with a ladder, he could see no signs of blight — giving him hope that his tree had somehow developed a defense against the fungus.
"I'm not in denial," he said, cradling a brown bur in his palm as he stared upward. "But show me one that big."
All claims of a naturally resistant American are "baloney," said Paul Sisco, a retired American Chestnut Foundation staff geneticist. This and other LSA's, he said, have just somehow managed to hang on a bit longer.
"These trees often die within a year or two of `discovery,'" said Sisco, past president of the foundation's Carolinas chapter.
But these survivors are playing an important role in the restoration effort.
Soon after the blight was discovered, the U.S. Department of Agriculture began trying to develop a hybrid that was resistant and would grow tall enough to produce marketable timber. Because Chinese and Japanese trees, unlike the American ones, had evolved along with the blight, the emphasis was on crossing native trees with the foreign ones.
"It didn't matter whether it looked like an American chestnut," said Kim Steiner, a professor of forest biology at Pennsylvania State University. The goal was simply "some sort of a timber tree."
After decades and millions of dollars, the government gave up. To be honest, purists weren't interested in what the government was after, said Steiner.
"We're not talking about replacing American chestnut," he said. "We're talking about restoring American chestnut."
Enter Charles Burnham.
A corn geneticist by training, Burnham was retired from the University of Minnesota when he read about the government's failed efforts. He began thinking about ways in which his own successful work with food crops might be applied to the chestnut conundrum.
In 1983, Burnham and several other plant scientists formed The American Chestnut Foundation — built on his program of "backcross breeding."
Burnham started out with a hybrid between an American and a Chinese chestnut, then backcrossed it with a "pure American." The progeny of that pairing were then backcrossed to American chestnut a second time; the offspring from that coupling were then crossed a third time back to American stock.
(The American Chestnut Cooperators Foundation — a smaller, but no less dedicated sister organization — is focused on grafting and intercrossing large native survivors to achieve a blight-resistant, all-American chestnut.)
Since an American chestnut parent always passes some of the blight-susceptible genes to its progeny, the backcross — or B3 — trees are then intercrossed among themselves so their progeny have a chance of inheriting resistant genes from both parents, said Fred Hebard, chief scientist at the organization's main research farms near Abingdon, Va.
The resulting B3F3 trees — third backcross, third filial generation — are, genetically, up to 94 percent American.
"The approach was a population of near-American chestnuts that would breed true for resistance," said Steiner.
The product of all that crossing, backcrossing and intercrossing is being put to the test at Hurst's and hundreds of other breeding orchards around the country.
The chestnuts on Hurst's property — some of which have grown to an impressive 20 feet in height — contain genetic material from three North Carolina "mother trees." Scattered among the "families," as a scientific control, are several offspring of a Chinese chestnut.
The trees that show the most resistance after inoculation will be used at the seed orchards to produce the next generation. All the rest — about 99 percent — will be destroyed, said Steiner.
"The quality of that seed coming out of that orchard will get better and better and better as more and more of the poor trees are removed," he said.
But as he told attendees at the Asheville summit, developing the tree is only half the battle.
At a resort overlooking the French Broad, the air was thick with hope and excitement as more than 300 scientists and lay people — young women in Crocs and Gore-Tex and gray-bearded men in plaid flannel shirts and hiking boots — gathered to swap stories and hear the latest news.
Hebard told the gathering that the orchards should be producing trees with "stable resistance" by 2023, nearly two decades sooner than originally projected.
But there were also sobering words.
In the past several years, the Forest Service has been planting test plots of chestnut in areas where it has allowed commercial logging. The results have been both promising and "disconcerting," said Stacy Clark, a forester at the agency's Southern Research Station in Asheville.
Seedlings are up to 30 percent shorter than pure Americans, Clark told the gathering. And some of the hybrids have also flowered earlier than the pure Americans, meaning they might be susceptible to frosts, Clark said.
Even if they can resist the blight, the trees will have to contend with threats from imported insects and other diseases.
"You're not going to get chestnut back through natural regeneration," Clark said. "We all know that. So you have to put it back in the woods."
Dr. Scott Merkle of the University of Georgia went a step further, broaching the touchy topic of cloning.
Currently, the organization produces backcrosses to American chestnut by time-consuming hand pollination. Hebard said the organization harvested 80,000 B3F3 seeds this year.
Using various advanced cloning techniques, commercial timber companies can generate enough seeds to plant 1 billion trees a year, Merkle said.
"Your progeny are all great. In fact, they're not even progeny. They're the same trees you started with — just a lot more of them," he said.
Even without cloning, there are those who will consider anything but a pure American an abomination, said Research Station Director Rob Doudrick, who was among the first to map the tree's genes.
"It conjures up all kinds of things in people's minds," he told the gathering. "The brakes go on. `Frankentree.' You know? ALL that kind of stuff."
But it was the hand of man that pushed this species to the brink, said Paillet, the Arkansas professor. And he said it's up to humans to try to restore some balance.
"We can't just let things go their natural course," he said. "Because we've disrupted things beyond the tipping point."
Regardless of how the trees are produced, they will need places to grow, mainly on privately-held forest land. Landowners, Steiner said, will have to be convinced that it's in their best interests to plant chestnuts. And though people at the conference hated to hear it, he said, "The world doesn't NEED chestnut timber."
"The restoration of American chestnut is a really impractical idea. Some people might say it's a nutty idea," Steiner acknowledged. But, he said, it is "a compelling idea..., a romantic idea..., an emotional idea. And that's where the motive comes from. That's where it has to come from to sustain this program."
Before his death, Peattie, the naturalist, was aware of work toward a blight-resistant hybrid. But he held out little hope for its success.
"All words about the American Chestnut are now but an elegy for it," he lamented. "... never again will those proud forests rise."
Jim Hurst and legions of others are on a mission to prove him wrong.
The American Chestnut Foundation http://www.acf.org
The American Chestnut Cooperators Foundation http://www.accf-online.org/
Allen G. Breed is a national writer, based in Raleigh, N.C. He can be reached at features(at)ap.org. Follow him on Twitter at http://twitter.com/(hash)!/AllenGBreed
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