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#           Refining the cheatgrass–fire cycle in the Great Basin: Precipitation timing and fine fuel composition predict wildfire trends      

      September 27, 2017    

Larger, more frequent wildfires in arid and semi-arid ecosystems have been associated with invasion by non-native annual grasses, yet a complete understanding of fine fuel development and subsequent wildfire trends is lacking. We investigated the complex relationships among weather, fine fuels, and fire in the Great Basin, USA. We first modeled the annual and time-lagged effects of precipitation and temperature on herbaceous vegetation cover and litter accumulation over a 26-year period in the northern Great Basin. We then modeled how these fine fuels and weather patterns influence subsequent wildfires. We found that cheatgrass cover increased in years with higher precipitation and especially when one of the previous 3 years also was particularly wet. Cover of non-native forbs and native herbs also increased in wet years, but only after several dry years. The area burned by wildfire in a given year was mostly associated with native herb and non-native forb cover, whereas cheatgrass mainly influenced area burned in the form of litter derived from previous years’ growth. Consequently, multiyear weather patterns, including precipitation in the previous 1–3 years, was a strong predictor of wildfire in a given year because of the time needed to develop these fine fuel loads. The strong relationship between precipitation and wildfire allowed us to expand our inference to 10,162 wildfires across the entire Great Basin over a 35-year period from 1980 to 2014. Our results suggest that the region's precipitation pattern of consecutive wet years followed by consecutive dry years results in a cycle of fuel accumulation followed by weather conditions that increase the probability of wildfire events in the year when the cycle transitions from wet to dry. These patterns varied regionally but were strong enough to allow us to model annual wildfire risk across the Great Basin based on precipitation alone.

## Citation Information

## Related Content

                  -              Data           
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August 4, 2017

####                 Combined wildfire dataset for the United States and certain territories, 1870-2015              

Forest and Rangeland Ecosystem Science Center

#### David S Pilliod

##### Supervisory Research Ecologist

Forest and Rangeland Ecosystem Science Center

dpilliod@usgs.gov

208-387-1363

#### Justin Welty

##### Biologist

Forest and Rangeland Ecosystem Science Center

jwelty@usgs.gov

208-387-1337

#### Robert S Arkle

##### Ecologist

Forest and Rangeland Ecosystem Science Center

rarkle@usgs.gov

208-426-5205

## Related Content

August 4, 2017

####                 Combined wildfire dataset for the United States and certain territories, 1870-2015              

Forest and Rangeland Ecosystem Science Center

#### David S Pilliod

##### Supervisory Research Ecologist

Forest and Rangeland Ecosystem Science Center

dpilliod@usgs.gov

208-387-1363

#### Justin Welty

##### Biologist

Forest and Rangeland Ecosystem Science Center

jwelty@usgs.gov

208-387-1337

#### Robert S Arkle

##### Ecologist

Forest and Rangeland Ecosystem Science Center

rarkle@usgs.gov

208-426-5205

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