Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2010
Publication Date: 11/3/2010
Citation: Davies, K.W., Bates, J.D., Svejcar, A.J., Boyd, C.S. 2010. Effects of long-term livestock grazing on fuel characteristics in rangelands: an example from the sagebrush steppe. Rangeland Ecology and Management. 63:662-669.
Interpretive Summary: Livestock grazing and wildfire occur on rangelands around the globe. However, the impacts of grazing on fuel characteristics are relatively unknown. The effects of grazing on fuels are important because fuels characteristics are one of the primary factors determining the risk and severity of wildfires. We evaluated the impacts of grazing on fuels by comparing grazed to non-grazed (livestock excluded in 1936) sagebrush steppe plant communities. Long-term grazing decreased fuel accumulation and height. These results suggest that grazing is reducing the risk and severity of wildfires on rangelands. This research identifies a new area of research; management impacts on fuels in rangelands. This information is of interest to land and resource managers because most rangelands are grazing and at risk of burning.
Technical Abstract: Livestock grazing potentially has substantial influence on fuel characteristics in rangelands around the globe. However, information quantifying the impacts of grazing on rangeland fuel characteristics is limited and the effects of grazing on fuels are important because fuels characteristics are one of the primary factors determining risk, severity, continuity, and size of wildfires. We investigated the effects of long-term (70+ yrs) livestock grazing exclusion (non-grazed) and moderate levels of livestock grazing (grazed) on fuel accumulations, continuity, gaps, and heights in shrub-grassland rangelands. Livestock used the grazed treatment through 2008 and sampling occurred in mid- to late-summer in 2009. Non-grazed rangelands had >2-fold more herbaceous standing crop than grazed rangelands (P < 0.01). Fuel accumulations on perennial bunchgrasses were approximately 3-fold greater in non-grazed than grazed treatments. Continuity of fuels in non-grazed compared to grazed treatments were also greater (P < 0.05). The heights of perennial grass current year’s and previous years’ growth were 1.3- and 2.2-fold taller in non-grazed compared to grazed treatments (P < 0.01). The results of this study suggest that moderate livestock grazing decreases the risk of wildfires in sagebrush steppe plant communities and potentially other semi-arid and arid rangelands. These results also suggest wildfires in moderately grazed sagebrush rangelands have decreased severity, continuity, and size of the burn compared to long-term non-grazed sagebrush rangelands. Because of the impacts fuels have on fire characteristics, moderate levels of grazing probably increases the efficiency of fire suppression activities. Because of the large difference between fuel characteristics in grazed and non-grazed sagebrush rangelands, we suggest that additional management impacts on fuels and subsequently fires need to be investigated in non-forested rangelands to protect native plant communities and prioritize management needs.