Skip to main content
U.S. flag

An official website of the United States government

Fire, livestock grazing, topography, and precipitation affect occurrence and prevalence of cheatgrass (Bromus tectorum) in the central Great Basin, USA


Matthew A. Williamson
Erica Fleishman
Ralph C. Mac Nally
Bethany A. Bradley
David S. Dobkin
Frank A. Fogarty
Ned Horning
Matthias Leu
Martha Wohlfeil Zillig



Publication type:

Scientific Journal (JRNL)

Primary Station(s):

Rocky Mountain Research Station


Biological Invasions. 22: 663-680.


Cheatgrass (Bromus tectorum) has increased the extent and frequency of fire and negatively affected native plant and animal species across the Intermountain West (USA). However, the strengths of association between cheatgrass occurrence or abundance and fire, livestock grazing, and precipitation are not well understood. We used 14 years of data from 417 sites across 10,000 km2 in the central Great Basin to assess the effects of the foregoing predictors on cheatgrass occurrence and prevalence (i.e., given occurrence, the proportion of measurements in which the species was detected). We implemented hierarchical Bayesian models and considered covariates for which[0.90 or\0.10 of the posterior predictive mass for the regression coefficient C 0 as strongly associated with the response variable. Similar to previous research, our models indicated that fire is a strong, positive predictor of cheatgrass occurrence and prevalence. Models fitted to all sample points and to only unburned points indicated that grazing and the proportion of years grazed were strong positive predictors of occurrence and prevalence. In contrast, in models restricted to burned points, prevalence was high, but decreased slightly as the proportion of years grazed increased (relative to other burned points). Prevalence of cheatgrass also decreased as the prevalence of perennial grasses increased. Cheatgrass occurrence decreased as elevation increased, but prevalence within the elevational range of cheatgrass increased as median winter precipitation, elevation, and solar exposure increased. Our novel time-series data and results indicate that grazing corresponds with increased cheatgrass occurrence and prevalence regardless of variation in climate, topography, or community composition, and provide no support for the notion that contemporary grazing regimes or grazing in conjunction with fire can suppress cheatgrass.


Williamson, Matthew A.; Fleishman, Erica; Mac Nally, Ralph C.; Chambers, Jeanne C.; Bradley, Bethany A.; Dobkin, David S.; Board, David I.; Fogarty, Frank A.; Horning, Ned; Leu, Matthias; Zillig, Martha Wohlfeil. 2020. Fire, livestock grazing, topography, and precipitation affect occurrence and prevalence of cheatgrass (Bromus tectorum) in the central Great Basin, USA. Biological Invasions. 22: 663-680.


Publication Notes

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.