JACKSON, Wyo. — It has been an intense wildfire season in Wyoming, but one species that relies on fire to regenerate and thrive is the quaking aspen.
In September, Buckrail met with Nate Wilson, a District Forester for the Wyoming State Forestry Division, to learn more about aspen ecology and how the species adapts to wildfire.
Quaking aspen, or Populus tremuloides that translates to “poplar that trembles,” is an early pioneer species that often populates a site after a wildfire disturbance. Aspens are considered a fire adapted species because their root system will quickly regenerate. A fire will stimulate aspen shoots to sprout from existing roots.
Quaking aspens differ from other tree species, where typically a single root system results in one tree. An entire stand of aspen can originate from one root system. An aspen stand’s roots will continue to sprout, creating more and more clones.
“Technically, they all have the same genetics,” Wilson said. “They are one individual.”
According to the U.S. Forest Service, trunks can live for a hundred years, but the root system can be hundreds or thousands of years old. An aspen stand in Utah’s Fishlake National Forest, called Pando, is considered the world’s largest organism, covering 106 acres and weighing an estimated 13 million pounds. While Pando’s root system is estimated to be 80,000 years old, it is more common for aspen clones to be 5,000 to 10,000 years old.
Wilson explained that a wildfire can speed up the reproduction process of aspen clones.
“A wildfire can kill portions of their roots, but in general what we see is the more intense the fire, the better response we get,” Wilson said. “When we get a really hot fire, that’s when we get thousands and thousands of stems per acre of aspen regeneration.”
A young tree will grow faster than the slowly growing conifers, enabling aspen to dominate in a grove for many years. Over time, as more shade-tolerant conifers, including subalpine fir, Douglas fir, Engelmann spruce, etc., become more dominant, the aspen stand gets crowded out and cannot regenerate. In Wyoming, there’s been a significant movement in the past 10 to 15 years to revive aspen stands.
“There has been a decline in aspens stands,” Wilson said. “We have a lot of aspen stands that are very late in the forest successional process because we put out a lot of wildfires for so long.”
“We have a lot of aspen stands that are very late in the forest successional process because we put out a lot of wildfires for so long.”
Nate Wilson
In the absence of a wildfire, mechanical treatments can help encourage the production of new aspens. Crews will use chainsaws to cut down conifers, and the burning of the branches will help reinvigorate aspen growth. Aspens also need direct sunlight, so removal of the shade understory will assist with a stand’s stability. Other mechanical treatments include cutting aspen stems or disturbing the soil around the aspen root system.
According to Wilson, firefighters like to see healthy aspen stands because the trees can actually decrease wildfire severity, and are considered a useful tool in fire management. Additionally, aspen stands support a healthy ecosystem by providing a variety of grasses and forbs for a number of species, including elk, mule deer and moose.
“They are a beautiful tree,” Wilson expressed. “They are definitely a critical part of the landscape in our area.”
