The impact of fire on Northern Plains grasslands has become a hot issue in the wake of the Pautre wildfire near Lemmon, S.D., this spring.
In April, more than 14,000 acres were scorched by a prescribed burn that got out of control. I twas started U.S. Forest Service officials trying to revive 130 acres of crested wheatgrass on the Grand River National Grassland.
The fire has sparked a number of questions about whether fire should be used to manage grasslands. says Kevin Sedivec, North Dakota State University Extension range management specialist.
"Is fire good or bad? Does it destroy, and do we "lose," these rangelands? Does a need really exist for prescribed burns on range management? These are common questions that need to be addressed for land managers to better understand the role of fire in managing range and grasslands in the Dakotas," Sedivec says.
Data documenting the impacts of fire on plant species composition and forage production in the Dakotas is limited, he says.
"What we know is early spring fires, such as what was experienced during the Pautre fire, tend to have little impact on grassland plants in terms of plant composition or forage production," Sedivec says. "These types of fire will remove standing dead plant tissue, release nutrients for plant growth, improving water cycling, and increase the nutritional quality and taste of plants that livestock and wildlife would normally ignore."
He says an excellent example of the value of a prescribed early spring fire is that it removes unpalatable crested wheatgrass plants, which are replaced by new crested wheatgrass plants that are lush and desirable to grazing animals. This practice provides a higher nutritional grass that livestock readily consume, rather than ignore, while allowing the native vegetation to grow and not be overgrazed. Through time, the invasive, exotic crested wheatgrass can be reduced from the plant community and replaced by many native grass species.
Late-spring (mid-May to early June) fires tend to be excellent in providing short-term production losses of invasive grasses such as Kentucky bluegrass and smooth bromegrass, Sedvic says. These fires generally increase the production and composition of warm-season native grasses with little impact to cool-season native grasses.
In the eastern Dakotas, late-spring fires tend to increase the overall forage production, especially warm-season grasses such as big bluestem, switchgrass, Indiangrass and prairie sandreed. In the western Dakotas, these types of fires tend to have no effect on native plant species' composition and little to no effect on forage production. However, during dry springs, these fires can reduce the short-term forage production potential.
"The impact of summer fire is really unknown and quite variable," Sedivec says. "These types of fires tend to occur when environmental conditions include high temperatures and limited precipitation. Summer fires not only remove the above-ground plant material, but also create bare soil that can become hot, impacting the recovery period and possibly decreasing short-term forage production potential."
Environmental conditions must be considered when evaluating the impact of summer fires, he adds. However, summer fires appear to injure exotic, invading cool-season grasses such as Kentucky bluegrass and smooth bromegrass.
Late-summer and early fall fires appear to have no impact on plant species' composition based on limited studies conducted in western North Dakota. These fires may decrease forage production potential during the subsequent year following the fire, but production fully recovers 12 to 24 months following the fire, depending on moisture conditions.
This type of fire severely injures club moss, a pesky weed found on western rangelands of the Dakotas, and kills juniper trees and some shrubs. Although juniper trees should grow on specific landscapes and habitats, many of these trees should not be growing on the true rangeland sites. When these invaded tree sites are burned, the native plant species' composition increases as the trees die off, creating a more sustainable, properly functioning ecosystem.
These benefits clearly indicate that fire is a tool that must be included in management strategies for rangeland and grasslands in the northern Plains, Sedivec believes.
"Fire not only can be used to manipulate the grazing patterns of livestock, but it also can be used to control invasive grasses," he says. "Introduced cool-season grasses are North and South Dakota's No. 1 problem in negatively impacting the forage value, wildlife habitat quality, hydrology, nutrient cycling and the scenic beauty of our rangelands.
"Fire, in combination with grazing, is the best tool we have available to combat the invasion of exotic cool-season grasses and undesirable woody encroachment," he notes. "We will not stop the invasion of Kentucky bluegrass (better known as our lawn grass), smooth bromegrass, crested wheatgrass or woody encroachment onto native range without fire."