Historically, fire was a ubiquitous component of the Great Plains environment, interacting with other components, such as bison whose grazing patterns resulted in uneven fuel distribution and therefore in diverse fire effects. The frequency of historic fires varied throughout the Great Plains, from every two to three years in the eastern tallgrass prairies, to three to four years in the Nebraska Sandhills, six to twenty-five years in mesic-to-xeric northern mixed-grass prairies, and five to ten years in the western shortgrass prairies and desert grasslands.
Fire effects vary with frequency, season-ofoccurrence, and location. Generally repeated fires in any season affect diversity by favoring grasses over forbs. Dormant-season fires remove litter and thus may both encourage undesirable plants, such as smooth brome (Bromus inermis), sweet clover (Melilotus spp.), and Kentucky bluegrass (Poa pratensis), and expose soil to surface erosion. However, dormant- season fires have less of an effect on ground-nesting birds and invertebrates. Latespring fires, the season of most eastern grassland prescribed burning, favor the dominant, warm-season species such as big bluestem (Andropogon gerardii) over cool-season species like Kentucky bluegrass, but they often have a major impact on the invertebrate community. Summer (growing-season) fires, which historically occurred most frequently but were smallest in size, reduce plant diversity by favoring grasses over forbs. These fires are less likely to affect invertebrates or ground-nesting birds and are most successful in top-killing woody plants that invade and degrade unburned prairies.
Individual species, however, do not all respond similarly to fire. Thus maintaining a diverse fire regime, interactive with other ecosystem-level components such as grazing, is essential to the long-term, ecological diversity and dynamics of Great Plains grasslands.
Thomas B. Bragg University of Nebraska at Omaha
Bragg, Thomas B. "Climate, Soils and Fire: The Physical Environment of North American Grasslands." In The Changing Prairie, edited by Kathleen H. Keeler and Anthony Joern. Oxford: Oxford University Press, 1995: 49– 81.
Bragg, Thomas B., and Lloyd C. Hulbert. "Woody Plant Invasion of Unburned Kansas Bluestem Prairie." Journal of Range Management 29 (1976): 19–24.