Post-fire rangeland recovery highlighted
Following Wyoming’s second worst wildfire year in terms of acreage burned, wildfire recovery efforts were a hot topic during the Wyoming Stock Growers Association Winter Roundup Convention and Trade Show, held Dec. 9-11, 2024 at the Ramkota Hotel and Conference Center in Casper.
During the Progressive Rancher Forum on the first morning of the event, Dr. Brian Mealor, a University of Wyoming professor and the director of the Sheridan Research and Extension Center, discussed post-fire recovery of rangeland forages.
Fire history
To begin, Mealor outlined the instance of wildfire throughout Wyoming’s history.
“We’re much more of a fire-prone landscape than we think we are in parts of the state,” he said. “And, fire is not necessarily strange to what we manage for in Wyoming.”
Mealor displayed a map showing high fire activity across the forested mountain ecosystem in the northwest part of the state, over to the grasslands of northeastern Wyoming. He pointed out a noticeable gap in the southwest corner.
“The northeastern corner of the state is more of a Great Plains type of rangeland setting, and as we move south and west, we get into more of a true sagebrush grassland situation,” he explained. “I think there are some different responses that manifest themselves based on where we are in the state, and I think they are tied to a few key things.”
According to Mealor, these include a higher proportion of rhizomatous grasses in the eastern part of the state and a history of shorter fire return intervals in the west.
“There’s some evidence suggesting in the western part of the state, there may have been up to 300 years between naturally occurring fires historically,” he noted.
Post-fire grazing
Mealor further noted the ability to manage for diverse and healthy rangeland communities or predict vegetation trajectory following a fire depends on a few key aspects.
These include fire intensity, fire severity, weather, precipitation and pre-fire vegetation composition.
He pointed out one of the most frequently asked questions from producers following a fire is how long they should rest pastures before grazing.
To answer this, he cited findings of several research studies conducted in Wyoming and Montana comparing grazing intensity over time following a fire.
“There was a slight tendency grazing in the first year reduced perennial grass biomass, especially when they got up to 50 percent utilization, but we kind of expect this because animals are grazing the only biomass there,” Mealor stated. “Then, if we look at the second year after the fire, we saw a tendency to have more perennial grasses.”
He continued, “If we see an increase in annual grasses following a fire, in many cases, it isn’t the first year or two after a fire. Sometimes it takes three to four plus years for annual grasses to ramp back up and either be where they were pre-burn or maybe even exceed those pre-burn levels in some cases.”
Additionally, these studies found post-fire grazing resulted in a tremendous increase in annual bromegrasses, including Japanese and downy bromegrass.
Ultimately, Mealor noted, “The thing I want to point out, especially in the Great Plains system, it’s not a foregone conclusion a fire is going to shift to annual grass dominance, especially if there was an annual grass dominance before the fire.”
However, he noted this pattern is species specific.
“If we look at Western wheatgrass, which is bulletproof in a lot of ways – it stands up to grazing, fire and many of our herbicide treatments – so grazing the year following the fire did not seem to negatively affect the composition the next year,” he said.
On the other hand, grasses like needle and thread and bunchgrass tend to be a little more susceptible to grazing and may see a decline in production.
“The take home here is it’s probably not going to hurt plant community composition to take time off from grazing following a fire,” he concluded. “But, if there is a situation where grazing is necessary on those sites and they get some precipitation before spring, it’s not a nail in the coffin to graze those sites appropriately.”
Invasive grasses
Mealor noted it’s hard to have a post-fire rangeland recovery discussion without bringing up invasive grasses.
“I think we have excessively publicized the relationship between fire and cheatgrass to some extent,” he admitted. “But there is some really interesting new research showing fire needs cheatgrass more than cheatgrass needs fire.”
With this, Mealor explained fire isn’t the sole perpetrator of a cheatgrass problem – there must be a seed source that is able to respond to the disturbance.
He nodded to some observational studies based in the Thunder Basin which found sites with less than 20 percent annual grass cover had a lower likelihood of annual grasses becoming dominant after a fire than sites with greater than 20 percent annual grass cover.
“So, we’re kind of faced with an interesting trade off regarding where we should try to invest in some post-fire annual grass control, and I think it would make the most sense on sites where we knew we had problems beforehand,” he explained.
“One of the silver linings is there may be a window of opportunity to reestablish desirable plants on burn sites before cheatgrass or other annual invasives start to ramp up,” he added.
Ventenata is another invasive grass plaguing the state of Wyoming, and while little is known about ventenata’s response to fire, data from Oregon suggests ventenata does not react positively or negatively to fire disturbance.
“Whether the monitoring sites in the study were burned or not burned, the frequency and cover of ventenata continued to march forward and get worse,” Mealor shared. “I guess in one way, it means it’s predictable and we should just continue to work our strategy for this species.”
Sagebrush
To conclude his presentation, Mealor noted Wyoming is home to half of the best sagebrush grasslands in the nation, and recently there has been a large push to conserve these habitats.
“Historically, it took quite a long time before sagebrush naturally came back after a fire. Areas with annual grasses makes this even more difficult because sagebrush seedlings are puny competitors, especially where there is a high density of annual grasses,” he explained. “I would also say it’s hard for sagebrush to recover on sites with good perennial grass cover as well.”
“But, in places where we were able to reduce grass competition over the long term, we’ve seen some pretty tremendous sagebrush growth in just a year,” Mealor added.
The good news for producers is grazing has been found to be an effective method for reducing grass cover and encouraging sagebrush growth post fire.
Mealor reiterated this by mentioning research done in eastern Oregon which tracked the growth of sagebrush transplants in areas with and without livestock grazing. The study ultimately found areas that were grazed had a greater instance of sagebrush reestablishment over time.
“Overall, I think many of the places where we had severe fires this year are probably going to be in pretty good shape in a couple of years if we are able to manage them correctly,” he concluded. “In the meantime, I will pray for rain and snow – hopefully we will get it.”
Hannah Bugas is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
