CORVALLIS, Ore. A new study suggests that the decline of aspen groves in Yellowstone National Park during much of the past century may be at least partly due to the absence of wolves.

The loss of native aspen groves in Yellowstone and other areas of the Rocky Mountains is reaching crisis proportions, experts say, having declined as much as 50-90 percent in certain areas.

Now, scientists have outlined in more detail the magnitude of the aspen decline in Yellowstone National Park, and developed a new theory for the trees decline within the park. It links those declines to the loss of wolves, a key predator species, and their interactions with elk and bear populations.

The study was done by Eric Larsen, with the Department of Geosciences at Oregon State University, and William Ripple, professor of forestry and director of the OSU Environmental Remote Sensing Applications Laboratory. It was just published in the journal Biological Conservation.

This hypothesis is not yet proven, and were working closely now with National Park Service biologists in more than 115 permanent research plots to test the theory, Larsen said. What is clear is that the wolves disappeared during the same era that the successful development of mature aspen stands ground to a halt.

The loss of aspen, scientists say, is an ecological crisis thats poorly appreciated by much of the public. Aspen not only adds scenic beauty to the landscape with their rich golden fall color, but they are often the only significant hardwood present in these conifer-dominated ecosystems. Groves of aspens, which are biologically rich with herbs, shrubs, insects, birds and berries, offer a diversity of plant and animal life often exceeded only in riparian zones in the mountain West.

Using historic documents, aerial photographs, and dendrochronological, or tree ring dating techniques, Ripple and Larsen determined that Yellowstone Park aspen successfully recruit
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Contact: Bill Ripple
bill.ripple@orst.edu
541-737-3056
Oregon State University
11-Sep-2000