Patch Burn Grazing Management in a Semiarid Grassland: Consequences for Pronghorn, Plains Pricklypear, and Wind Erosion

Abstract

Management strategies that allow for spatiotemporal interactions between fire and herbivores can potentially achieve multiple management goals related to livestock production and wildlife conservation, but little is known about such interactions in semiarid grasslands where fire has traditionally been viewed as having few management applications. We studied patch burn grazing management in the shortgrass steppe of northeastern Colorado, comparing unburned pastures to pastures where 25% of the area was burned in October or November each year over 4years. Our objective was to examine the interactive effects of patch burns and the subsequent response by pronghorn (Antilocapra americana) on plains pricklypear (Opuntia polyacantha) and wind erosion rates. We monitored abundance of plains pricklypear and wind erosion rates throughout the experiment and quantified seasonal pronghorn densities and postburn damage to plains pricklypear cladodes during the latter 2years of the study. Pronghorn density was 26 times greater in winter and 7 times greater in spring on patch burns compared with unburned pastures. By late winter, densities of bitten or uprooted plains pricklypear cladodes were five times greater on patch burns compared with unburned pastures. Patch burns, as well as the subsequent response of pronghorn, reduced plains pricklypear density by 54–71% during the first year after the burns, and density remained suppressed for up to 6years after burns. Wind erosion rates on patch burns were greater compared with unburned pastures but were two orders of magnitude lower than rates measured on fallow croplands in the region. Autumn patch burns can be a valuable means to suppress plains pricklypear and thereby increase grass available for livestock consumption in the shortgrass steppe. These outcomes can be achieved without increasing wind erosion in a manner that threatens long-term soil sustainability and without negative consequences for livestock weight gains.