ST. GEORGE — Quaking aspen is an iconic species – it is to Utah’s mountains what sagebrush is to the state’s deserts. While the tree can be found throughout North America, its most impressive specimen grows in the Beehive State.
Known as Pando, the 106-acre, 13-million-pound aspen stand is actually a single organism and widely regarded as the world’s largest (potentially the oldest, too). And its time is running out.
“Pando’s health and long-term existence is highly-threatened,” said Paul Rogers, director of the Western Aspen Alliance and associate professor at Utah State University. “If it’s been around this long and it’s falling apart on our watch, the finger points directly back at humanity.”
But it’s not logging, pollution or foot traffic that’s threatening Pando’s immediate future. Instead, the superlative aspen stand is threatened by a combination of climate change and long-term herbivory from deer, elk and cattle –though the deer are the primary offenders, Rogers said.
Pando is situated in Fishlake National Forest, and the aspen stand is actually bisected by State Route 25, which accesses the lake and the numerous recreation sites nearby. There is a resident deer herd that spends summers in the vicinity of Pando, and it’s this group and other seasonal browsers that prey on the gargantuan tree at its most vulnerable.
Aspen are clonal species, meaning they reproduce through a network of roots that connect all the stems (what look like individual trunks). To grow or replace dying stems, aspen send up new shoots or saplings in a process called “suckering.”
These suckers are perfect forage for deer and other herbivores that may encounter them before they develop into mature stems. Since aspen stems are much shorter-lived than a single pine tree or juniper, it’s critical that enough suckers survive for the aspen colony to maintain its size and health.
To buy some time for Pando to recover and to further research the effect of herbivory on the massive aspen, about half of the tree’s total area is surrounded by fencing installed by the U.S. Forest Service and volunteers.
“We’re giving it a little room to breathe with these fences, but I would suggest that’s maybe not the ultimate solution,” Rogers said. “What’s inside the fence is just as artificial as what’s outside it.”
Rogers compared fenced portions of the tree to an outdoor museum, preserving something from its natural environment rather than within it. While the U.S. Forest Service has considered increased fencing, it’s not convinced that herbivores alone are causing the decline of Pando.
“We think that herbivory is playing into that, whether it’s by deer or livestock,” said Kurt Robins, district ranger with Fishlake National Forest. “But there are other factors going on, because we have areas where those things are excluded and we’re still struggling to get the regeneration that should be occurring.”
Robins said climate change is the greatest long-term threat to Pando, particularly continuing drought that would deprive the tree of much-needed precipitation.
A widespread decline in aspen might actually accelerate the drought. As much as aspen need water, they also have been shown to recharge soil faster and increase runoff compared to other native trees, helping more water reach desert towns throughout Southern Utah and the West.
In fact, aspen have several advantages and are considered a keystone species for the habitat they occupy.
“The fluttering leaf that it gets its name from – that fluttering lets in more light to the forest floor, which allows more species to grow,” Rogers said. “If you look at an aerial photograph of a large landscape, where the aspen is there’s water underneath. Finally, the deciduous leaves make the soil richer, and in many landscapes in the West aspen is the only deciduous tree.”
All these factors combine to make aspen stands second only to riparian forests in biodiversity within the Intermountain West. Robins said aspen are highly productive and essential species, and they even have the added benefit of great aesthetic value that attracts significant recreation.
So far, it’s been hard for both the U.S. Forest Service and researchers like Rogers to pin down exactly what the future holds for aspen, and by extension Pando.
“Aspen is not dying everywhere,” Rogers said. “There are some threats from climate change, but there are some immediate threats that we can do something about this year or next year as opposed to the decades looking at climate change. There are too many herbivores, both domestic and wild, and we should address the mismanagement of the past.”
The U.S. Forest Service continues to collaborate with volunteers and scientists to help Pando, in part through service projects that maintain fencing and remove weeds and in lending support to more creative endeavors aimed at helping the trembling giant.
During a recent photographic survey, a team of citizen scientists used high-tech cameras to photograph the extent of Pando and create an inventory of more than 8,600 high-definition, 360-degree images of the vast tree.
Ryan Thalman, associate professor of chemistry and natural resources at Snow College, served as the science advisor for the 8-day undertaking.
“Because we’re tagging all the photos and doing a comprehensive inventory, someone can dig into a particular area and look at bark health, understory cover or tree density,” Thalman said. “I think it will be a positive tool for other people to use as they continue to study the tree and look at what’s stressing it.”
Ultimately, the fate of a tree that’s history spans millennia may be decided by the actions taken in the next few years. Like the network of roots that connect each aspen stem, the collaboration and sharing of resources between all stakeholders may be the key to protecting Pando’s future.
“It’s my desire that the Pando brings us together, whether you’re a rancher, outdoors enthusiast or environmentalist,” Robins said. “We all should find common ground that we want it to continue to sustain itself. I think that the Pando is symbolic of that – we’re all connected and that we all need to work together.”
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