Wildfire: Healing the hills

JACKSON HOLE, Wyo. — Fire can be a devastating and powerful force. Initial observations and thoughts of wildfires in our open spaces tend to gravitate around the destruction they cause.

Much of the West has been hit hard in recent years by wildfires, including Wyoming. Last year the majority of the 176,000-acre Mullen Fire burned within the state’s border in the southeast portion of the state. Whether it is from a distance or up close, it is difficult to not notice the remnants the fire left behind.

However, fire also can be a benefit to forests and its inhabitants—albeit over time. Biologists with the Wyoming Game and Fish Department toured the Mullen Creek Fire burn area by aircraft and on foot this summer to assess the impacts of the wildfire on wildlife habitat, and they saw some positive changes.

Patchwork of burns

Right away, biologists noted a natural mosaic—or mixture—of burned and unburned areas within the perimeter of the wildfire, and a variation in burn intensity across the landscape. While the areas that burned hotter will take longer to recover, biologists are optimistic the fire produced long-term benefits for mule deer, elk, moose and bighorn sheep.

“We saw interesting fire behavior where one hillside was 100 percent consumed, and then an adjacent hillside was left unburned,” said Ryan Amundson, Game and Fish terrestrial habitat biologist in Laramie. “The word mosaic applies well to this fire.”

The mosaic of burned and unburned areas can create a range of vegetation age classes and high-quality forage in big game seasonal ranges. Following the Mullen Fire, the U.S. Forest Service mapped the severity of the burned area, and it was a mixed bag. Fire intensity was much higher in areas of high conifer densities, and as of late June many of those areas had seen little-to-no new vegetation growth. However, areas with low-to-moderate fire severity should recover within the next several years.

“We are already seeing this in areas outside of heavy conifer stands where grasses and forbs are regenerating,” Amundson said. “There’s still a lot of bare ground in areas that burned with higher intensity, and these areas will take a while to grow back. This is especially true in areas that had high conifer density before the fire because they lacked understory vegetation to start with. Now that these areas are cleaned up, there’s an opportunity for grasses and forbs to return. But this will be a slow process.”

From the ashes

Following the Badger Creek Fire in southeast Wyoming in 2018, it took about three years for grasses and forbs to return to some areas. The path a fire takes as it burns can determine the severity of damage to vegetation.

Backing fires, which burn down a slope and are slower burning, tend to burn shrubs into the root crown and kill the plant. A fire that moves up a slope burns faster and can leave more of a plant’s woody skeleton behind. This causes less damage to the root crown and results in better resprouting following a wildfire.

“I like to see shrub skeletons left; it gives me hope that the fire severity wasn’t too high. When it is table-top flat that tells me it was hot and intense, and the plant is likely dead,” Amundson said.

Shrub regeneration following a wildfire also can depend on topography. Amundson said there has already been some shrub regeneration on north-facing slopes from the Mullen Fire, but those areas may not be available to wildlife in the winter due to high snow depths.

Conversely, Amundson noted the more arid, south slopes will take longer to regenerate due to lack of water and competition from cheatgrass—an invasive plant in Wyoming. Because it thrives in disturbed areas, cheatgrass has already invaded many south-facing slopes in the Mullen Fire burn area. In response, more than 9,000 acres was aerially treated with herbicide to control cheatgrass this summer, and more acres will be treated in 2022.

“We need to continue to watch for cheatgrass invasions post-wildfire. Its presence can affect native, perennial vegetation recovery and also result in altered fire frequencies in the future,” Amundson said.

While cheatgrass is quick to move in after a disturbance, other plants are a bit slower to respond to the benefits from a wildfire. Aspen suckers, which sprout from aspen roots and allow trees to reproduce quickly if damaged or stressed, started to appear in late June, some of which were 12 to 18 inches tall.

Fire typically stimulates a strong suckering response in aspen. In other wildfires, such as the 2012 Squirrel Creek and the Badger Creek fire, aspen response has been good.

“Of all the treatments we do for aspen, fire gives us the greatest number of sprouts per acre compared to other treatments,” Amundson said. “Clear-cutting or other mechanical treatments may give us several hundred aspen sprouts per acre, while fire results in several thousand per acre.”

Many wildfires occur in the summer, but the Mullen Fire started in September and burned for more than two months.

“As a result, we are seeing a delayed aspen regeneration response,” Amundson said.

Good from the bad

Below-normal levels of precipitation resulted in good and bad news for the Mullen Fire burn area. Riparian areas, which naturally help control erosion, showed patchy burn scars across the footprint of the fire with some loss of willows.

Precipitation was between 50 to 65 percent of normal in much of the Platte River watershed in May. While the lack of moisture slowed vegetation growth, it also minimized sediment finding its way into rivers and streams, which is good news for fish and other aquatic life.

Amundson said grasses are already recovering quickly in riparian areas, and some willows are showing signs of resprouting. Areas along North and South Mullen Creek, portions of Douglas Creek and the main stem of the North Platte River showed higher fire severity than other riparian areas. Due to steep topography, these areas have a limited riparian vegetation band along waterways, which normally reduces the impact from wildfires.

“The streams should be able to handle the sediment loads in the future with some vegetation regrowth in the riparian areas to hold the soil in place,” Amundson said.

Depending on precipitation amounts and intensity throughout the remainder of the summer, these areas could see increased ash, sediment and woody debris deposits into the river corridors. Overall, wildlife managers are optimistic that this wildfire will be ultimately beneficial for big game animals.

“In the next two to three years we should see a lot of good come from this fire,” Amundson said. “Mule deer summer ranges should be positively affected, and in the Platte River and Savage Run Wilderness areas many acres of bighorn sheep habitat have likely been created by this fire. Recent helicopter flights showed bighorns have moved into areas they have not historically used due to high conifer densities. The sheep have better line-of-sight visibility now with the conifers gone.”

For habitat recovery, patience is key. Biologists will continue monitoring regrowth and how wildlife respond to the new landscape.

This story is written by Robin Kepple who is the information and education specialist for the Laramie region, and is a regular contributor to Wyoming Wildlife magazine.