"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."