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Aspen trees make comeback in Yellowstone National Park

Posted at 10:16 AM, Oct 08, 2018
and last updated 2018-10-08 12:16:35-04

YELLOWSTONE NATIONAL PARK – The golden hues of fall are starting to give way to colder temperatures, but this year it seemed like Yellowstone National Park was displaying more color than ever.

A mature aspen stand that survived the fires of 1988 was luckier than trees in the other parts of the park. It turns out that catastrophic fire joined with everything from ancient volcanoes to wildlife have brought the aspen back all across Yellowstone.

Yellowstone National Park Biologist Roy Renkin knows Yellowstone aspen well. He’s been watching it grow since 1984. In this time he has seen a change of wildlife change the status of these trees.

“With the reintroduction of wolves back in ’95,” he said.

That’s when there were between 16,000 and 19,000 elk wintering on the northern range in Yellowstone.

“A decade ago, you’d be able to see in things like this willow,  all the willow was hedged back to this point, right here.”

Now, with half the number of elk on the land, aspen groves that had been reduced to a few mature stands, now show a range of young, medium and old trees.

“Over time it has been really interesting to see how the aspen has responded,” said Renkin.

But as is often the case in Yellowstone, there’s no single explanation for the return of the aspen. The fires of 1988 also played an important role.

“One of the biggest surprises though, as the forest began to develop was all these aspens that showed up,” said Renkin.

When the young aspen started popping up through the burned forest floor, that was big news.

“Because we really had no documentation that aspen did indeed come and establish in burned areas,” said Renkin.

And it happened all over the park. “It blows my mind that summer of 1989 how much aspen seed was deposited out on the landscape,” said Renkin.

Where the aspen does best, the soil is sandy — and you can thank ancient volcanoes and especially the glaciers for that.

“It just sets the stage for plants that establish down here, just to love it because all the moisture that’s in the soil is available to the plants,” said Renkin.

Like so much in the park, aspen groves are a study in change. They come and go over the decades and centuries.

A grove will be replaced by different trees that live longer or adapt to the soil or climate better. Then, a lifetime later, fire may sweep through and a new cycle begins and future generations will again enjoy bright aspen colors on a crisp fall day.

Renkin says aspen groves that escape wildfires will be replaced by Douglas Fir trees, but that will take about 140 years.

-John Sherer reporting for MTN News