Winter grazing can reduce wildfire size, intensity, and behavior in a shrub-grassland

Authors: Davies, Kirk; Boyd, Chad; Bates, Jonathan - Jon; Hulet, April

Submitted to: International Journal of Wildland Fire
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: 2/15/2016
Publication URL: http://handle.nal.usda.gov/10113/61906
Citation: Davies, K.W., Boyd, C.S., Bates, J.D., Hulet, A. 2016. Winter grazing can reduce wildfire size, intensity, and behavior in a shrub-grassland. International Journal of Wildland Fire. 25:191-199. doi: 10.1071/WF15055.

Interpretive Summary: Wildfires are an ecological and economic risk for many semi-arid rangelands which has resulted in increased demand for pre-suppression management of fuels. Grazing is likely the only fuel treatment that is cost effective to apply at the landscape scale in rangelands. We evaluated winter grazing as a fuel treatment in sagebrush rangelands because it can be applied at little cost. Winter grazing compared to no grazing decreased area burned, flame height, frame depth, rate of spread, burn temperatures, and heat loading. The cumulative effect of winter grazing on fire behavior and intensity reduces wildfire risk and potential severity.

Technical Abstract: 1. An increase in mega-fires and wildfires in general is a global issue that is expected to become worse with climate change. Fuel treatments are often recommended to decrease the risk, size, intensity, and severity of wildfires; however, the extensive nature of rangelands limits the use of many potential treatments. Dormant season grazing has been suggested as a fuel treatment in rangeland, but its effects on fire characteristics have not been evaluated. 2. We investigated the influence of dormant season grazing (winter grazing in the study ecosystem) by cattle Bos taurus on fuel characteristics, fire temperature and heat loading, flame height and depth, and area burned in Wyoming big sagebrush Artemisia tridentata subsp. wyomingensis shrub-grassland communities at five sites in southeastern Oregon, USA. Winter grazing was applied for five years prior to burning and compared to ungrazed areas. 3. Winter grazing decreased fine fuels and increased fine fuel moisture, which reduced fire temperature, heat loading, flame height and depth, rate of spread, and area burned. 4. Winter grazed areas had lower maximum temperature and heat loading during fires than ungrazed areas and thereby, decreased risk of fire-induced mortality in important plant functional groups, such as native perennial bunchgrasses. 5. Synthesis and applications: The effect of winter grazing on fuel and fire characteristics reduces the risk, size, and intensity of wildfires and likely increases the effectiveness of suppression efforts. These results suggest that winter grazing, when properly applied, may be an effective fuel management treatment that can be applied across vast shrub-grasslands to decrease wildfire risk and fire intensity to mediate climate change effects on wildfire activity. Winter grazing may also reduce wildfire suppression expenditures in rangelands where fine fuel accumulation is an issue and in A. t. subsp. wyomingensis rangelands decrease the risk of habitat loss from wildfires for sagebrush-associated wildlife of conservation concern including sage-grouse Centrocercus urophasianus.