FLAGSTAFF — Beneath the beautiful yellow and red leaves of towering aspens in the Kachina Wilderness, forest ecologist Mike Stoddard looks down. His focus isn’t on the bright fall foliage, but on what’s growing beneath the forest floor. Mr Stoddard hopes historical data will inform the future of these beloved orchards, seeking landmarks for trees planned 20 years ago.

Stoddard and colleagues at Northern Arizona University’s Ecological Restoration Institute compared recent discoveries with data collected more than 20 years ago and found alarming trends in aspen tree recovery in the southern outcrop of the San Francisco Mountains. A new study was published in October that revealed that

The study found that environmental factors related to climate change, such as drought and heatwaves, as well as animal grazing and wildfire management, are contributing to the decline of aspen trees in the region. Stoddard warned that this decline could have major ecological implications for the overall health of the forest, especially since some trees are not growing back.

Known as a disturbance-loving species, poplars are stimulated by large disturbances at the ground level, such as wildfires. Despite the trees’ resilience and rapid recovery, researchers found that prolonged drought and unmanaged animal grazing are reducing the number of young poplars reaching maturity.

Without active management, these combined factors could lead to declines in aspen populations and the loss of diverse forest ecosystems in the San Francisco Peaks, a popular spot for locals and tourists. Researchers warn that there is. When a live poplar tree dies, there may be no new growth to replace it.

“Canary species” in the forest

The poplar is the most widely distributed tree in North America, with its southernmost range in the Sky Islands of the southwestern United States and pockets of Mexico. Trees diversify forest species, serve as nesting sites for birds, and provide stability to ecosystems by retaining moisture.

Although poplars can produce seeds, the most successful method of propagation occurs when new shoots known as “suckers” grow from the root system of an existing tree. The new buds are clones of the original tree, and many cloned poplar trees can grow from the same root system.

Aspen clones are some of the largest living organisms on Earth. The single poplar clone, known as the “Pando” clone, is located in the Fish Lake National Forest in southern Utah and spans more than 100 acres. This cloning network has been recognized by the Guinness Book of World Records as the “largest plant.”

This type of regeneration is also why aspen trees thrive after wildfires. When a fire clears an area, aspen roots can go dormant beneath the soil, and new suckers rise to the surface, quickly reforesting the affected area faster than other types of trees. .

Forest health: Rapid spread of tiny insects threatens survival of Arizona poplar trees

In the San Francisco Peaks, we are seeing this successful regeneration in areas affected by the 2022 Pipeline Fire. In the two years following the fire, aspen stands regenerated with new shoots that grew without competition from other tree species and are now too tall for moose to graze.

But aspen trees in the lowlands of the San Francisco Mountains are experiencing a bottleneck effect in their growth, according to NAU researchers. The suckers are growing back after the disturbance, but are unable to reach maturity due to a lack of resources due to moose grazing and prolonged drought and rising temperatures.

These groves, which Stoddard described as “canary species,” provide clues about the declining health of the mountaintop forests and all aspens in the species’ southern range.

“Aspen communities with southern exposure in these lowlands are declining,” Stoddard said. “It’s important to monitor these ecosystems at the edge. They’re going to provide information about how things are changing.”

Poplars contribute to Flagstaff’s fall foliage

Tourists flock to Flagstaff every September and October to enjoy the outdoors and enjoy the bright fall colors of the aspen trees. The city’s tourism bureau, Discover Flagstaff, displays a “leaf meter” on its website when the leaves are at their brightest. The website received nearly 80,000 views in October and was featured on a Phoenix-based television station.

“It was the most popular page on our site for the month,” Ryan Randazzo, media relations manager at Discover Flagstaff, said in an email to The Republic. “Overall traffic to our site increased by 17% in October this year…and Leaf-Meter was the main driver.”

Tourism to Flagstaff generates $565 million in economic impact for the city and employs approximately 8,000 people.

“While we can’t say the fall foliage is the only reason people visit Flagstaff in September and October, there’s plenty to see and do here year-round. For the past 20 years, we’ve chosen hotels and motels for those months. “We’ve seen occupancy rates increase,” Randazzo said.

Fewer colors: Do the autumn leaves look a little calm? Autumn in Arizona is becoming warmer and drier.

Aspen’s future in jeopardy

Beneath the white trunks of towering aspens, Stoddard looks at the slender plants poking out of the ground, searching for clues to the fate of the mountaintop forest.

“This is the future,” Stoddard said, grasping a discreet growth that barely exceeded his height. Once a poplar clone grows above a certain height threshold, its chances of reaching maturity increase significantly.

New aspen swathes near the study area were suddenly stunted by elk grazing.

Rocky Mountain elk, which live in the San Francisco Mountains, are not native to Arizona. In 1912, 83 elk were transplanted from Yellowstone National Park to Arizona, increasing the state’s population to about 35,000, according to the Arizona Game and Fish Department.

In the absence of natural predators, the elk population near Flagstaff is managed through the issuance of hunting permits. Because state and federal agencies have limited ability to fence wild aspen stands, forest managers are looking to these hunting permits as a tool to help young aspens reach maturity.

In the aftermath of the 2010 Schultz Fire, which burned more than 15,000 acres northwest of Flagstaff, the U.S. Forest Service and Arizona Game and Fish will increase the availability of elk hunting permits to support aspen tree regeneration. A cooperation agreement was signed.

“Land managers, wildlife managers and forest managers recognized the need to protect aspen buds,” Stoddard said. “So they came together and launched an effort to increase hunting pressure on elk so they could stimulate some of this regeneration and help the elk grow into trees.” “

It’s too early to tell whether the measures have been effective, but Professor Stoddard is optimistic after seeing poplar trees recover from the burn scars from the 2022 pipeline fire. This region was not included in the study.

Aspen trees can survive disasters such as wildfires, but the overlapping pressures of prolonged drought and uncontrolled elk grazing put other mountaintop aspen forests at risk of disappearing over the next century. Exposed.

“If (Aspen) doesn’t commit resources to the future, it’s only a matter of time,” Stoddard said. “They need disturbance, but not all disturbance leads to reproduction.”

John Leos covers environmental issues for the Arizona Republic and Az Central. Send your tips or questions to john.leos@arizonarepublic.com.

Environmental reporting on azcentral.com and The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust.

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This article originally appeared in the Arizona Republic. NAU study finds young poplar trees near Flagstaff facing multiple threats