Biological Invasions

, Volume 20, Issue 6, pp 1493–1506 | Cite as

Cheatgrass (Bromus tectorum) distribution in the intermountain Western United States and its relationship to fire frequency, seasonality, and ignitions

  • Bethany A. BradleyEmail author
  • Caroline A. Curtis
  • Emily J. Fusco
  • John T. Abatzoglou
  • Jennifer K. Balch
  • Sepideh Dadashi
  • Mao-Ning Tuanmu
Original Paper


Cheatgrass (Bromus tectorum) is an invasive grass pervasive across the Intermountain Western US and linked to major increases in fire frequency. Despite widespread ecological impacts associated with cheatgrass, we lack a spatially extensive model of cheatgrass invasion in the Intermountain West. Here, we leverage satellite phenology predictors and thousands of field surveys of cheatgrass abundance to create regional models of cheatgrass distribution and percent cover. We compare cheatgrass presence to fire probability, fire seasonality and ignition source. Regional models of percent cover had low predictive power (34% of variance explained), but distribution models based on a threshold of 15% cover to differentiate high abundance from low abundance had an overall accuracy of 74%. Cheatgrass achieves ≥ 15% cover over 210,000 km2 (31%) of the Intermountain West. These lands were twice as likely to burn as those with low abundance, and four times more likely to burn multiple times between 2000 and 2015. Fire probability increased rapidly at low cheatgrass cover (1–5%) but remained similar at higher cover, suggesting that even small amounts of cheatgrass in an ecosystem can increase fire risk. Abundant cheatgrass was also associated with a 10 days earlier fire seasonality and interacted strongly with anthropogenic ignitions. Fire in cheatgrass was particularly associated with human activity, suggesting that increased awareness of fire danger in invaded areas could reduce risk. This study suggests that cheatgrass is much more spatially extensive and abundant than previously documented and that invasion greatly increases fire frequency, even at low percent cover.


Bromus tectorum Fire regime alteration Grass-fire cycle Invasive grass Invasive plant Moderate Resolution Imaging Spectroradiometer (MODIS) burned area product 



We thank E. Fleishman, J. Finn, N. Horning, A. Mahood, N. Mietkiewicz, and R.C. Nagy for valuable discussion. E. Fleishman, S. Hanser, M. Holton, M. Jesus, M. Lavin, A. Mahood, B. Rau, and L. Turner greatly assisted this project by providing percent cover data. This research was supported by the National Aeronautics and Space Administration Terrestrial Ecology Program under Award NNX14AJ14G and the Joint Fire Sciences Program 15-2-03-6.

Supplementary material

10530_2017_1641_MOESM1_ESM.xlsx (120 kb)
Histograms of predicted percent cover for different bins of observed percent cover and contingency table calculator for different mapped percent cover thresholds


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Department of Environmental ConservationUniversity of MassachusettsAmherstUSA
  2. 2.Graduate Program in Organismic and Evolutionary BiologyUniversity of MassachusettsAmherstUSA
  3. 3.Department of GeographyUniversity of IdahoMoscowUSA
  4. 4.Earth Lab, CIRESUniversity of ColoradoBoulderUSA
  5. 5.Department of GeographyUniversity of ColoradoBoulderUSA
  6. 6.Biodiversity Research Center, Academia SinicaTaipeiTaiwan

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