Rare Burst of Blooms Shows Bright Side of Wildfires
for National Geographic News
|July 1, 2002|
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U.S. National Park and Forest employees in the Appalachian Mountains were surprised this spring to come upon a highly unusual floral display: The forest was carpeted with thousands of white flowers of a plant that rarely blooms. The plant, known as turkeybeard, or mountain asphodel (Xerophyllum asphodeloides), is a rare species of lily.
It is a state-listed endangered or vulnerable species in portions of its Appalachian range and is included in the U.S. Center for Plant Conservation's National Collection of Endangered Plants.
Very few turkeybeards bloom in a given year. But the forest floors of two Virginia sites, George Washington National Forest and Shenandoah National Park, are covered with more than 25,000 of the plants. They have produced thousands of pompom-like blossoms of about 200 small flowers atop stalks 1.5 meters (4.5 feet) high. At least one impressive plant produced 27 stalks.
"None of the current park or forest employees has ever seen anything like this," said Norm Bourg, a research fellow at the Smithsonian Institution-National Zoological Parks Conservation Research Center in Front Royal, Virginia. His work has been funded by the National Fish and Wildlife Foundation, the Smithsonian Institution, the University of Maryland, and the U.S. Forest Service.
Bourg said the unusual display, which also occurred in 2001, is the result of forest fires that burned through the sites in 1999. The situation offers a case that underlines the importance of fires to the overall health of forest ecosystems.
Fire, ecologists and other scientists point out, is a component of natural cycles of forest growth and maintenance.
Plants and animals have evolved in response to periodic disturbances in ecosystems, including fire, said Steve Croy, an ecologist for the George Washington National Forest. "An ecosystem is never really static," he said. "The only constant is change." The situation is more complicated today, he added, because people have altered the magnitude and frequency of such disturbances through technology.
Doug Raeburn, a fire ecologist at Shenandoah National Park, said many of the forest fires today that do widespread damage "are fires started by people under the entirely wrong conditions."
In recent weeks, thousands of people have been forced out of their homes and at least 1.5 million acres have been burned by raging fires in several areas of the United States.
Yet restricted and carefully controlled fires can benefit forest ecosystems, Raeburn said. Fires clean forest floors of a heavy buildup of leaves, twigs, and dead vegetation that might otherwise accumulate and help fuel fires to potentially hazardous levels, he noted.
For most of the past 70 years, staff in national parks and forests suppressed the majority of fires. After assessing the ecological benefits of fire, forest officials began to change that policy.
Now, officials at U.S. parks and forests around the country authorize limited burning in areas that are seen as likely to benefit from controlled fires, according to Valerie Baca of the U.S. Forest Service.
"There might be some short-term death," said Raeburn, "but the new life that comes from it is more vigorous and more diverse."
A more sensitive form of fire management is prescribed natural fires, which allow fires started by lightning to burn under specific conditions. Shenandoah National Park and the George Washington National Forest are now writing specific guidelines for such fires.
Boost to Growth
Bourg, a Ph.D. candidate at the University of MarylandCollege Park, has been investigating turkeybeards in the Appalachians to study how fire affects them ecologically. His major adviser, Douglas Gill, had started tagging the plants in 1990, before park and forest officials began setting limited fires to prune the undergrowth and reduce fuel loads.
In the absence of fires, turkeybeards are easily overlooked in forests and seldom produce flowers. The situation was much different after the sanctioned fires in 1996.
By 1998, the plants had resprouted vigorously and hundreds of spectacular flowering stalks had appearedfar more than had ever been recorded. Two additional prescribed fires in 1999 set the stage for the turkeybeards' rejuvenation and growth to their "super-plant" status this year. The plants need a year after a fire to recover before achieving maximum growth and blooming, Bourg said.
Massive fire-induced blooming may be a fire-adapted characteristic of the species, he said, and could explain the multiple stalk production seen on the lilies.
Fire also increases opportunities for pollen exchange among turkeybeard plants as a result of the mass-flowering. Bourg's experimental results have shown that flowers that receive pollen from other plants are more fruitful than those fertilized by their own pollen. Therefore, they produce more seeds, which leads to higher reproduction.
But burns indirectly benefit the plants as well. Fire literally paves the way for the lilies to enjoy a growth spurt, Bourg said. Forest fires reduce competition from other vegetation, open up tree canopies to admit more sunlight, and recycle nutrient-rich organic material by returning it to the soil.
During the recovery period after a fire, this extra sun and added nourishment enable turkeybeards, as well as other forest plants, to grow stronger and then initiate mass production and blooming.
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