The effects of fire and grazing in the northern mixed-grass prairie : implications from the Pautre wildfire

Current federal recommendations pertaining to the management of post-fire grazing on rangelands interrupts historic disturbance regimes of the North American prairies by indicating that fire and grazing should be separated by at least two growing seasons. In contrast, some scholars suggest that North American prairie evolved under a tight linkage of fire and proximate post-fire grazing and should be well adapted to these combined disturbances. The Pautre wildfire of April 2013 provided an opportunity to test the effects of post-fire grazing in the northern mixed-grass prairie. One grazing allotment, burned in its entirety, and three burned and nonburned sites spanning a north-south gradient of the fire perimeter were selected as study locations. The effects of grazing versus rest, defoliation during the first spring, summer, or fall following the fire on burned and nonburned sites and the effects of fire on forage fiber digestibility were tested. Sites grazed during the first two growing seasons following the fire were found to recover similarly to sites rested during that same time. In addition, defoliation during any season following the fire produced no negative effects when compared to nondefoliation. Increases in forage fiber digestibility peaked shortly after fire and were short-lived, diminishing by the following year. These results lend support to the theory that fire and grazing were historically linked disturbances throughout the evolution of the North American prairies, indicating that the federal recommendation of rest is unnecessary in at least the northern mixed-grass prairie ecoregion. Historic, evolutionary patterns of disturbances, such as fire and grazing, may be useful in determining the most appropriate post-fire management regimes for specific ecoregions.