Wildfires have two faces: the nemesis of mankind since settlement, and Mother Nature’s way of renewing aging, infested grasslands and forests.
The unintended consequence of widespread suppression of wildfires coupled with the trend toward grazing systems that promote uniformity has been the loss of plant and animal diversity within native grassland ecosystems, according to rangeland ecologists at several universities across the U.S. Great Plains.
Historical accounts suggest native grasslands burned frequently. Tall-prairie grasslands, for instance, burned every three to five years. The greening after a fire attracted wildlife that intensively grazed the burnt area for a year or so before moving on to newer burn areas. This gave the burnt-and-grazed area ample time to rest, regrow and build up enough mature forage and litter to carry the next fire and begin a new cycle of succession.
The result was a patchy mosaic of diverse habitats for grassland species that followed the succession of vegetation from burn patch to burn patch across the landscape. Grasses were the first to reappear and grazing kept growth in check to give forbs a chance to take hold beginning about a year later. As grazing pressure declined, grass species began to outcompete the forbs so that grasses dominated by years three and four after a fire. Each type of habitat supports certain wildlife species and some species need more than one type of habitat throughout their life-cycles.
Researchers have been developing this historic pattern of pyric herbivory (fire-driven grazing) into a grazing management system called patch-burn grazing, says Dr. Sonja Leverkus of Shifting Mosaics Consulting at Fort Nelson, B.C., who spoke on the concept at the British Columbia Cattlemen’s Association’s (BCCA) technology-transfer event at Fort St. John.
It’s simple because cows naturally follow fire to graze the high-quality forage in freshly burnt patches, and it’s inexpensive because there’s no need to put up cross-fences, develop water sources for paddocks, or gather and move cattle to control grazing, Leverkus explains.
U.S. studies indicate attraction to freshly burnt patches can override constraints such as topography and distance to water or shade. In one project on semi-arid rangeland, cattle selected riparian areas five times less often in a patch-burn grazing system than in traditionally managed pastures. Traditional management in most areas of the U.S. Great Plains is continuous grazing without burning, or after burning the entire pasture in spring. Complete burns carry the risk of severely limiting forage quantity early in the season and in a drought year.
Overall, cows on tall-grass prairie spent 75 per cent of their time grazing patches the year of burning. The finding that cattle on mixed-grass prairie in arid settings spent only 31 per cent of their time on burn patches in the burn year, suggests the attraction of burnt areas may be greater in regions with higher annual precipitation because of faster regrowth.
Although the initial intent of patch-burn grazing was to promote biodiversity on native grassland range, a few of the studies did assess its effect on cattle. The results show it didn’t hinder cow body condition scores, weaning weights or yearling weights and had the potential to benefit the cattle and the bottom line, compared to traditional grazing management practices.
Dr. Derek Scasta of the department of ecosystem science and management at the University of Wyoming says the high-protein regrowth in the first year after a burn and the rest periods offered to earlier burn patches provided by patch burning can sustain and even improve cattle gains. It can also mitigate the negative effects of drought, reduce parasite pressure and lessen the need for chemical or mechanical weed and brush control and nitrogen fertilizer, plus provide a management alternative to cross-fencing.
Leverkus is a certified Wildland Fire Practitioner and member of a North American team that helps ranchers and land managers in the U.S. and Canada plan and implement prescribed burns on grassland and forested ranges.
The rotation, timing and size of burn patches within a pasture will vary according to your conservation and grazing goals plus the productivity of the pasture. The system has worked well in areas as small as 100 acres and as large as 20,000 acres.
The fundamentals involve knowing how to establish effective natural and man-made fireguards and how weather conditions support effective and safe burning.
Stocking rate is the initial consideration when deciding how many patches to establish. A medium stocking rate based on the carrying capacity of the entire pasture is generally recommended. Too high a stocking rate will force animals to graze back over previously burned patches, reducing the fuel needed to carry a fire in the scheduled year. Too low, and the grass in the burnt patch will get ahead of the animals in the first year.
A three-year burn-return interval has been effective in areas with good moisture and decent growing conditions, whereas a four-year interval seems best in more arid regions, so the litter, or fuel as they call it, has time to rebuild sufficiently.
“There are a lot of questions about liability if a fire does get out of control, but I tell ranchers that they don’t have to feel alone. Working with someone who can help write a prescription can become part of the liability protection by providing documentation that supports your due diligence and proper management of fire,” she says.
Fuel load, wind speed, wind direction, temperature, humidity, advantageous points to light up, and documentation are all part of the proper prescription.
In Oklahoma and Texas, ranchers and landowners have formed prescribed fire associations with members supplying labour and equipment for each other. Some associations purchase group liability insurance packages that cover each member.
An online prescribed fire-training course is available through the Oklahoma Prescribed Fire Council.
Leverkus organized her own prescribed-fire school for ranchers last year and was hoping to put it on again this year. “One thing is for certain, there will always be fire on the land across Canada and there will always be an opportunity to be proactive about it.”
Burning in B.C.
Fire is quite widely used by northern and eastern B.C. ranchers, primarily to boost forage quality and beat back the encroaching aspen and coniferous forest.
The use of patch-burn grazing as a conservation strategy may also gain some new support as the BCCA explores the potential for paid ecosystem goods and services.
BCCA vice-president Brian McKersie of Canal Flats says BCCA fully supports the practice of prescribed burns to rejuvenate meadows and control brush but it requires a real public relations effort to keep everyone onside.
The benefits go beyond the ranchers themselves. Wildlife will share in the renewed meadows while the suppression of insect-borne infestations benefits the forest itself. Prescribed burns can be used to open up new areas for recreational and tourism while reducing the threat of wildfires by burning up excess fuel in the meadowlands.
It can also have a bit of a double-edged effect when it’s uncontrolled, as McKersie learned firsthand after a major forest fire burned across his Crown-land range in 1985.
“The benefit was unbelievable. It took out the underbrush and there was more grass, but now we have real in-growth of pine stands,” he explains.
The fire opened pinecones, releasing seeds that within 10 years formed a mat of small trees that is smothering the grass. The trees are too crowded and too small to ever be good for timber so it’s not worth thinning them out.
Recent plans for a prescribed burn to clean up this area only got as far as setting up fireguards when the weather turned sour. Then a herd of elk moved in and the burn was postponed for fear that there wouldn’t be enough regrowth to sustain them over the winter
In the end they cut and pushed up some of the thickets into a pile and burned them. It worked, but was a lot more time consuming and expensive than a prescribed burn.
Way up at Fort St. John on private rangeland near Mile 81 on the Alaskan Highway, Jack Thiessen’s family have been using fire to clear land, and renew meadows and hillsides since they moved there from Swift Current, Sask., in 1965.
“As kids we would ride the valleys up the creeks first thing in spring lighting the fires every two to three years. The fires burned into the bush a few yards before dying out and in that way, little by little we opened more land for grass. A lot of land in this area was cleared this way and burning is still commonly used by ranchers because getting rid of trees maintains good-quality grass,” Thiessen explains.
He rotates his burns so he covers the whole ranch every five or six years.
“We store grass in the areas we want to burn so there will be enough fuel to get a good burn. There’s only a one- to two-week window to burn in spring when the grass is dry enough on top and it’s moist enough on the ground and in the bush. We want to leave about two inches of stubble because we don’t want to burn the grass roots or topsoil. New grass pops up quickly because the soil is moist and warms up quickly,” he says.
During the past two springs he burned 2,500 acres and will add another 400 this spring to free grassland where he logged aspen this winter. Typically there isn’t much grass at all the first year after logging, but by the third year the area has good grass. By the fourth year, the aspen suckers will be about two feet tall and by year five the grass has such well established roots it can tolerate a burn to remove the suckers. Years six, seven and eight provide really good grazing before the suckers start to come back, indicating it’s time to burn again.