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United States Department of Agriculture

Agricultural Research Service

Research Project: DISTURBANCE ASSESSMENT AND MITIGATION OF GREAT BASIN RANGELAND

Location: Northwest Watershed Management Research

Title: Interactions among livestock grazing, vegetation type, and fire behavior in the Murphy wildland fire complex in Idaho and Nevada, July 2007

Authors
item Launchbaugh, Karen -
item Brammer, Bob -
item Brooks, Matthew -
item Bunting, Stephen -
item Clark, Patrick
item Davison, Jay -
item Fleming, Mark -
item Kay, Ron -
item Pellant, Mike -
item Pyke, Dave -
item Wylie, Bruce -

Submitted to: United States Geological Survey Technical Report
Publication Type: Government Publication
Publication Acceptance Date: August 28, 2008
Publication Date: August 28, 2008
Citation: Launchbaugh, K., Brammer, B., Brooks, M., Bunting, S., Clark, P., Davison, J., Fleming, M., Kay, R., Pellant, M., Pyke, D., Wylie, B. 2008. Interactions Among Livestock Grazing, Vegetation Type, and Fire Behavior in the Murphy Wildland Fire Complex , July 2007. U.S. Geological Survey Open-File Report 2008-1214. Reston, VA: USGS. P.42

Interpretive Summary: We have only a very limited understanding of the interaction of vegetation type and livestock grazing on the behavior and severity of extremely large rangeland wildfires, such as the Murphy Wildland Fire Complex which burned 650,000 acres in southern Idaho and northern Nevada during July 2007. A team of scientists, habitat specialists, and land managers was called together by Tom Dyer, Idaho BLM State Director, to examine initial information from the Murphy Wildland Fire Complex in relation to plant communities and patterns of livestock grazing. The team found much of the Murphy Complex burned under extreme fuel and weather conditions that likely overshadowed livestock grazing as a factor influencing fire extent and fuel consumption in many areas where these fires burned. In grassland vegetation, under less extreme conditions, livestock grazing may, however, provide a means to reduce fire rate of spread and fire-line intensity by reducing fine fuel loads, potentially benefiting wildland fire control on millions of acres of rangeland in the western U.S.

Technical Abstract: A series of wildland fires were ignited by lightning in sagebrush and grassland communities near the Idaho-Nevada border southwest of Twin Falls, Idaho in July 2007. The fires burned for over two weeks and encompassed more than 650,000 acres. A team of scientists, habitat specialists, and land managers was called together by Tom Dyer, Idaho BLM State Director, to examine initial information from the Murphy Wildland Fire Complex in relation to plant communities and patterns of livestock grazing. Three approaches were used to examine this topic: (1) identify potential for livestock grazing to modify fuel loads and affect fire behavior using fire models applied to various vegetation types, fuel loads, and fire conditions; (2) compare levels of fuel consumed within and among major vegetation types; and (3) examine several observed lines of difference and discontinuity in fuel consumed to determine what factors created these contrasts. The team found much of the Murphy Wildland Fire Complex burned under extreme fuel and weather conditions that likely overshadowed livestock grazing as a factor influencing fire extent and fuel consumption in many areas where these fires burned. Differences and abrupt contrast lines in the level of fuels consumed were affected mostly by the plant communities that existed on a site before fire. A few abrupt contrasts in burn severity coincided with apparent differences in grazing patterns of livestock, observed as fence-line contrasts. Fire modeling revealed that grazing in grassland vegetation can reduce surface rate of spread and fire-line intensity to a greater extent than in shrubland types. Under extreme fire conditions (low fuel moisture, high temperatures, and gusty winds), grazing applied at moderate utilization levels has limited or negligible effects on fire behavior. However, when weather and fuel-moisture conditions are less extreme, grazing may reduce the rate of spread and intensity of fires allowing for patchy burns with low levels of fuel consumption.

Last Modified: 8/29/2014
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