Study suggests aspen stands in the West are facing slow decline

Posted: Friday, May 27, 2005

LEAVENWORTH, Wash. — In a tangle of snowberry brush, vine maple, and bitter cherry, and under a canopy of ancient towering aspens, Heather Kranz searched for clues to a disappearing species.

The 17-year-old amateur forest sleuth pushed through the thick underbrush, occasionally dropping to her knees to rustle through damp, musty leaves layered inches thick on the ground.

But she couldn't find what she was looking for on a cool, overcast morning earlier this month. In this centuries-old stand of aspens clogged with dense brush and surrounded by mature conifers, Kranz could find no evidence of any new aspen trees sprouting in at least the last two decades.

''I'd say this stand is dying,'' she said resolutely. ''There's no new growth. These trees are ancient.''

''Its days are numbered,'' said Mick Mueller, an ecologist for the Okanogan and Wenatchee national forests, as he examined the trees for signs of disease and decay.

Stands of white-barked aspens across the West are facing a similar fate. Decades of fire suppression have left the sensitive trees unable to compete in forests overcrowded with pine and fir trees and shrubs.

Historically, frequent, low-intensity fires burned away trees and brush and encouraged new growth in aspen populations, which sprout from a massive, fire-resilient root system, Mueller said. The tree is known for its distinctive bark and fluttering leaves and valued as prime elk, deer and bird habitat.

Without fire or other disturbances, the massive, interconnected root systems that link entire stands of aspens put all their energy into the larger trees, which emit a hormone that suppresses new sprouts. Those trees, which have little tolerance for competition, are slowly being overrun by conifers and shrubs. The root systems, which can live and produce trees for thousands of years, are shrinking. The majority of aspen stands on the Okanogan and Wenatchee forests are now believed to be less than two acres in size.

Until recently, land managers have paid little attention to the tree species. But a study by forest pathologist Jim Hadfield of the Pacific Northwest Forestry Sciences Lab in Wenatchee brought the aspen situation to light last year, when he found that nearly half the aspen stands in the two forests are in a state of decline, and the majority are so small that they are in danger of disappearing.

A few champions of the trees, like Hadfield and Mueller, are determined not to let that happen. That's how Kranz and other advanced biology students at Cascade High School ended up surveying aspen stands in the Wenatchee River ranger district for class credit this spring.

Armed with a GPS unit, measuring stick, tape measure and a clipboard, Kranz and classmates Julianna Simon, 17, and Laauren Martin, 18, spent about four hours studying two aspen stands. They counted trees, recorded the width and overall condition of a sample of them, marked down any evidence of disease or animal damage, and made an educated guess on the number of trees per acre.

One of the stands covering about two acres had a handful of large conifers blocking the sun. The students found just one new aspen sprouting.

From there, the students walked up a ravine in search of their second survey area. What they found was a strangled stand of aging aspens choked by thick brush and fallen trees. Massive aspens scarred by bear claws towered overhead, stealing most of the nutrients from any potential new sprouts.

The youngest tree Simon and Martin could find was about 20 years old.

''If we don't do anything here, they will eventually all be gone,'' said Mueller, who visited the site with the students.

The two aspen stands are among 30 that students are surveying this spring for the U.S. Forest Service. The agency has little historical data to use for comparison. But the stands are thought to have been considerably bigger in years past, some measuring several hundred acres in size, according to Hadfield's study.

Of the 105 stands surveyed in the two forests, nearly 60 percent measured two acres or less, and many had fewer than five living trees. Less than half the stands had active sprouting, and a quarter of the trees surveyed were dead. Many of the mature trees were infected with a decay fungus. According to the study, aspen stands are thought to be declining across the interior West, largely due to fire suppression, encroachment by conifer trees, and overgrazing by wild and domestic animals.

The most active new growth in the two local forests was found in the Chelan and Entiat ranger districts, in areas burned by wildlife in recent years. Prescribed burns and thinning are considered to be the best option for treating aspen stands, Mueller said. But land managers face an uphill battle.

''There is no commercial value for the trees; there's no market for the wood,'' Mueller said. ''The work doesn't pay for itself. So we have to look elsewhere for funding opportunities to do it.''

He said elk preservation groups offer some money, but there's little money within the Forest Service for aspen studies or restoration work. Some of the work now being done is ''bootlegged'' onto other forest restoration projects by forest workers who care about the trees' survival, Hadfield said.

''There are little pockets of aspen champions out there who have taken the tree under their wing,'' he said. ''Without that help, it will continue to be a slow, ongoing decline for this species.''

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