AR-News: Wolves linked to tree recovery
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Wed Oct 29 18:57:18 EST 2003
Wolves linked to tree recovery
By MIKE STARK
Gazette Wyoming Bureau
Reintroduced wolves appear to be playing a major role in the resurgence of
streamside trees and shrubs in certain portions of in Yellowstone National
Park, according to two new studies by scientists at Oregon State University.
When wolves were absent from the park, from the 1920s until the mid-1990s,
elk grazed heavily and repeatedly on young cottonwoods, aspen and willows.
Since wolves have returned, the elk have been forced to be more mobile,
which has meant easing up on certain feeding spots.
"Wolves are the top of the food chain," Bill Ripple, an OSU forestry
professor who has been studying aspen and other species in Yellowstone since
1997, said Tuesday. "Wolves affect elk and elk affect species like aspen."
In recent years, young cottonwoods and willows have been especially robust
in areas where elk may have once browsed but now feel the threat of wolves,
including places where they have few ways to escape, Ripple said.
"If they're boxed in against a canyon wall or a cutbank on a river -- those
seemed to be the places which are showing more growth," Ripple said.
Meanwhile, low-risk sites for elk are still being consumed and show little
growth, according to the studies.
The findings of the studies were recently published in the journals
Ecological Applications and Forest Ecology and Management.
The idea behind the studies is to examine the effect that wolves are having
in the Yellowstone ecosystem beyond simple predation on elk and other prey.
"With the restoration of wolves in Yellowstone, for the first time we have
the full suite of top carnivores," Ripple said. "That is a grand experiment
for us to take notice of what the connections are between different animals
Ripple acknowledged that the results of the studies are still "somewhat
preliminary" because wolves have only been back in Yellowstone since 1995.
Still, researchers say it's hard to ignore the hypothesis that there's a
strong connection between the return of wolves and the revival of certain
plants and trees.
"The data show a clear and remarkable linkage between the presence of wolves
and the health of an entire streamside ecosystem," said an announcement from
OSU about the studies.
In some areas on wintering range for elk, researchers found hundreds of
short cottonwood seedlings among cottonwoods that were 70 years old or
older, but very few trees that had not been chewed off before they passed
the seedling stage.
"Long-term elk browsing has been preventing any seedling from getting
taller," Robert Beschta, a forestry professor emeritus at OSU, said about
one area along the Lamar River.
Scientists said they were able to see a clear connection between the removal
of wolves in late 1800s and early 1900s and a decline in species such as
cottonwoods and aspen.
"I considered a variety of potential reasons that might explain the
historical decline of cottonwoods that began in the 1920s and have continued
up to the last couple of years," Beschta said in a statement Tuesday. "I
looked at climate change, lack of floods, fire suppression, natural stand
dynamics, and numbers of elk. But none of those factors really explained the
problem. Ultimately, it became clear that wolves were the answer."
Without fear of wolves, the elk were allowed to browse anywhere they liked
for decades, the scientists said. Killing off cottonwoods, willows and other
streamside shrubs allowed for increased erosion and effects on birds,
insects and other wildlife, they said.
"Before the wolves came back, it was pretty clear that in some areas we were
heading toward an outright extinction of cottonwoods," Beschta said.
Streamside shrubs and cottonwoods in places such as the Lamar Valley have
rebounded since the reintroduction of wolves, growing taller and becoming
more prevalent, the scientists said.
"There's this domino effect from wolves to elk to trees," Ripple said.
The OSU researchers caution that their studies aren't an encompassing look
at Yellowstone and the effects of wolves, but it is an indication that the
wolves appear to have stopped a major decline in the survival rates of
cottonwoods and willows.
"One point that should not be missed is this is actually great news for the
potential recovery of cottonwood trees and mature willows in Yellowstone
National Park," Ripple said. "We now have a pretty good idea why they were
in decline and the return of wolves should help pave the way for their
recovery. Even though it may take a very long time, for a change it looks
like we're headed in the right direction."
Copyright © The Billings Gazette, a division of Lee Enterprises.
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would say, "Well, I am for it!" This is how strongly I feel in this regard.
I will continue to be a vegetarian even if the whole world started to eat
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Isaac Bashevis Singer
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