Patch burn grazing management in a semiarid grassland: Consequences for pronghorn, plains pricklypear and wind erosion

Authors: Augustine, David; Derner, Justin

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2014
Publication Date: 3/5/2015
Citation: Augustine, D.J., Derner, J.D. 2015. Patch burn grazing management in a semiarid grassland: Consequences for pronghorn, plains pricklypear and wind erosion. Rangeland Ecology and Management. 68:40-47.

Interpretive Summary: Management strategies that allow livestock and other herbivores to respond to the distribution of prescribed fires in rangelands can help managers achieve multiple goals related to livestock production and wildlife conservation. We studied patch burn grazing management in the shortgrass steppe of northeastern Colorado, where we compared unburned pastures to pastures where 25% of the area was burned in October or November each year. Both livestock (cattle) and native ungulates (pronghorn antelope) were allowed to move in response to the distribution of the burns. Throughout the experiment, we monitored abundance of plains pricklypear cactus and wind erosion rates. During the latter two years of the experiment, we quantified seasonal pronghorn densities on and off the burns, and measured how much they damaged prickly pear plants by feeding on them. Pronghorn density was 26 times greater in winter and 7 times greater in spring on patch burns compared to unburned pastures. Late in the winter, densities of bitten or uprooted cactus plants were 5.2 times greater on patch burns compared to unburned pastures. Patch burns, and the response of pronghorn to those burns, reduced pricklypear density by 54 – 71% during the first year after the burns, and density remained low for up to 6 years after burns. More wind erosion occurred on patch burns compared to unburned pastures, but the rate of wind erosion on burns was extremely low compared to rates on fallow croplands in the region. Fall patch burns can be a valuable means to suppress pricklypear cactus and thereby increase grass available for livestock consumption in shortgrass rangelands. Furthermore, patch burns can enhance forage availability for pronghorn and create breeding habitat for grassland birds of conservation concern such as the mountain plover. These outcomes can be achieved without increasing wind erosion in a manner that threatens soils, and without negative consequences for livestock production.

Technical Abstract: Rangeland management strategies that allow for spatial and temporal interactions between fire and herbivores can achieve multiple management goals related to livestock production and wildlife conservation in mesic grasslands and savannas. Less is known about integrated management of herbivores and fire 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. Throughout the experiment, we monitored abundance of plains pricklypear (Opuntia polyacantha) and wind erosion rates. During the latter two years of the experiment, we quantified seasonal pronghorn (Antilocapra americana) densities and post-burn damage to pricklypear cladodes. Pronghorn density was 26 times greater in winter and 7 times greater in spring on patch burns compared to unburned pastures. By late winter, densities of bitten or uprooted pricklypear cladodes were 5.2 times greater on patch burns compared to unburned pastures. Patch burns, and the subsequent response of pronghorn, reduced pricklypear density by 54 – 71% during the first year after the burns, and density remained suppressed for up to 6 years after burns. Wind erosion rates on patch burns were greater compared to unburned pastures, but were 2 orders of magnitude lower than rates measured on fallow croplands in the region. Fall patch burns can be a valuable means to suppress pricklypear and thereby increase grass available for livestock consumption in the shortgrass steppe. Furthermore, patch burns can enhance forage availability for pronghorn and create breeding habitat for grassland birds of conservation concern such as the mountain plover (Charadrius montanus). 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.