The Bighorn National Forest is located in north-central Wyoming and spans over a million acres. Within the forest are several species of pine, spruce, fir, and aspen.
"The majority of our tree species here in the Bighorns is lodgepole pine," said Jacob McCarthy, District Forester for the Wyoming State Forestry Division. "Aspen accounts for about one percent of the entirety of the Bighorn National Forest."
This abundance of lodgepole pine is cause for concern, according to McCarthy. Diversity amongst the trees in a forest helps prevent disease and allows the ecosystem to be productive. There are two aspects to forest diversity: different ages of trees and different types of trees.
Currently, it is more common to use management techniques to promote age diversity in the Bighorns. Most often, this is in the form of clearing trees in an area.
The trees that are cleared are chosen based on specific objectives that land managers decide. These objectives could include things like targeting older trees or targeting areas that are more susceptible to fires.
While regrowth is likely to be of the same tree species, age diversity amongst the lodgepole pines makes the landscape more resilient because the trees are then less susceptible to illness.
But increasing age diversity is only one of the benefits of clearing trees like lodgepole pines..
"Those trees start to out-compete the aspens for the soil or water nutrients in the ground because there's a finite amount," said McCarthy.
With fewer lodgepole pines in the area, there is less competition for new species, usually aspens, to grow and succeed in the forest, which is what forest managers like McCarthy want. This promotion of aspen growth is called aspen enhancement.
"Aspen is what we call a deciduous tree," said McCarthy. "It does not contain the compounds that are more flammable that you have within pine and spruce, so they're a little less susceptible to fire."
While aspens can still burn, they do not burn as quickly as coniferous tree species like pine and spruce, so they’re often used in forests to promote diversity and protect the area. Aspens also have a lot of resiliency -- once aspens are in an area of the forest, they generally stick around.
"It is one of the first tree species that we tend to see repopulate a site after a major disturbance," said McCarthy.
He also said they have an important impact on the area’s big game species because increasing forest diversity with aspens adds more than just trees to the ecosystem.
"[Aspens] bring in a diverse group of plants and insects that live within these micro-ecosystems of the forest and that increases wildlife habitat through cover as well as food," said McCarthy.
Aspen enhancement has only been done a handful of times in the Bighorns, but McCarthy said they are looking to do it more through the Pole Creek Vegetation Management Plan. The Forest Service is in the process of deciding the specifics of the project. The National Environmental Protection Act (NEPA) review will be completed in 2024.
"Our national forest systems are very much multiple use," said McCarthy. "And we try to utilize the tools within our toolbox to conserve our systems so that we can see enjoyment out of them for all the values they give us."
