Quaking, Indeed 

Sawtooth forest study focuses on decline of aspen groves

Once upon a time, deep in an Idaho forest, there lived an aspen tree. The tree grew, drew praise for its autumn foliage and reproduced until aspen became one the largest organisms in Western forests.

But the aspen did not live happily ever after.

Over time, cows moved in, disease spread, fires were extinguished, and many of the aspen stands died. Foresters estimate that more than 60 percent of the aspen groves in the West have been lost. Now the U.S. Forest Service wants to change the aspen story in at least one Idaho forest. Their plan would kill one species of tree, in an effort to save another.

"We are very concerned about the decline of aspen in this area," said David Skinner, a wildlife biologist on the Sawtooth National Forest. "The primary cause of this decline is encroachment of conifers and lack of natural fire."

Skinner said plans to remove conifer trees on up to 100 acres of aspen stands within the Ketchum Ranger District over the next five years would prevent groves of aspen from being completely lost due to competition from taller trees. The proposal calls for the cutting of conifers within aspen stands that are 12 inches in diameter or less. (Think Christmas tree size.) No snags or trees with nests would be removed and the conifers that are cut would be left to decay naturally.

This selective thinning could help reverse the effects of fire suppression, overgrazing and disease that helped put a dent in Western aspen stand populations, Skinner said.

"It's cumulative [and] it's all happening at the same time," he said.

Forests are constantly changing; sequences of events give rise and fall to different species at different times. One species may hit a climax in population, then eventually give way to a new species as fire clears the landscape of the aged flora that often wins the competition for sun and nutrients. Fire-damaged trees turn into rotting trees and may offer a new species the sun and food they need to thrive.

"There's always that succession that runs through [a forest] and the cycle may take longer than our lives," said Gary Moen, a horticulture instructor at Boise State.

But some ecologists believe the decline of aspen in the Western Rocky Mountain region is not part of a natural cycle and can be measured in our lifetimes. Canadian Forest Service researchers estimate that as many as 30 percent of aspen in the Edmonton, Alberta region may have been wiped out within the last five years alone. Drought, heat, bugs and fungus are all partially blamed for the Canadian decline, while ecologists are still trying to account for the 10 percent decline in Colorado aspen forests.

A lack of wildfires can stunt the growth of a species that regenerates itself by sprouting new growth from existing root systems, Skinner said. Rather than reproducing by seed, the aspen's large, interconnected root system produces shoots that can live hundreds of years. Some consider the aspen the forest's largest organism because of this interconnection of one generation of stands to another. And when fire attacks the landscape, aged systems get a boost of new growth as aspen stands quickly rebound when the roots sprout new shoots that don't have to compete with the older trees killed by fire. Frequent fires also kill young conifer saplings that would eventually crowd the aspens, according to the U.S. Forest Service.

Fire is also nature's antidote to disease. Skinner said that aspen trees could use a good dose of fire to kill what ails the stands. The 2006 fire season ranks as one of the most destructive in Idaho's history books, but the big fires, fueled by thick undergrowth that flourishes when flames are suppressed are too consuming to give aspen stands the gentle pruning they need. Small, frequent fires could maintain the health of the aspen ecosystem but fire suppression efforts have put a halt to minor flare-ups.

Forest Service officials also blame the cow for the decline in Idaho aspen stands. Skinner said that plans to leave the felled conifer lying around the aspen groves could create physical obstacles that might deter cows from grazing on aspen. The shoots are something of a treat to cows, apparently, and it doesn't help that many stands are near water, said Gene Bray, advisory board member of the Western Watersheds Project, a Hailey-based environmental group that works to protect and restore watersheds in Western states.

"After years and years of grazing you will end up with mature trees and no young trees," Bray said. "And to be fair, elk [kill aspen] as well, but elk less so because cows hang out in the riparian areas. Elk will take their drink of water then leave." As cattle hang out at water sources and graze on the aspen, stands not only decline but the riparian areas are destroyed by the hooves of 1,000-lb. cattle. The trampling changes the soil topography, depletes vegetation that provides shade and dislodges sediment. Eventually these depleted waterways can dry up, starving aspen of a water resource. Although the Western Watersheds Project is focused more on grazing and cows, a different group of scientists suggests another animal could give aspen a chance at survival.

A 2000 Oregon State University study suggested that the decline of aspen in Yellowstone National Park over the last century could be due to the decline in wolves. The Oregon State researchers noted that elk have been grazing on aspen for centuries but wondered why the population of aspen stands has declined only in the last century. They connected the decline in aspen to the shrinking wolf population that typically hunts elk.

Forest Service officials don't want to wait to see if the recent delisting of wolves from the Endangered Species List would boost aspen numbers in Idaho. They want to hear public comment on the plan that would cut conifer trees within aspen stands. Bray said it's time to focus on the iconic tree.

"It used to be that aspen was so prevalent in the West that nobody worried about them," Bray said.

Send comments on the U.S. Forest Service plan by Oct. 6 to Ketchum Ranger District, PO Box 2356, Ketchum, Idaho 83340 or e-mail comments to comments_intermtn_sawtooth_ketchum@fs.fed.us.

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