Refining the cheatgrass–fire cycle in the Great Basin: Precipitation timing and fine fuel composition predict wildfire trends. Issue 19 (25th September 2017)

• Record Type: Journal Article
• Authors: Pilliod, David S.; Welty, Justin L.; Arkle, Robert S.
• Is Part Of: Ecology and evolution. Volume 7:Issue 19(2017:Oct.)
• Page Start: 8126
• Page End: 8151
• Publication Date: 2017-09-25
• Subjects: annual forb -- Bromus tectorum -- climate -- litter -- sagebrush shrublands -- weather; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.3414
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: 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. Abstract : We investigated the complex interactions of weather, fine fuels, and wildfires in the Great Basin. We found that both native and non‐native grasses and forbs influence the number of fires and area burned suggesting that cheatgrass is not the sole driver of the grass–fire cycle in this region. We also found that consecutive wet years and consecutive dry years result 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, a pattern that could be mapped and used to increase fire preparedness and plan fuel reduction.