Rates of change in invasive annual grass cover to inform management actions in sagebrush ecosystems

Abstract

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  The extent of annual grass invasions in sagebrush ecosystems has required land managers to prioritize treatments in strategic locations to influence invasion outcomes. Maps of invasive annual grass cover show the extent and severity of the invasion, but they do not illustrate how invasive cover is changing over time.
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  The rate of change in invasive annual grass cover describes the trajectory of invasion. This information can be used to fine-tune priority locations and strategies for invasive species treatments.
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  We identified locations with positive, neutral, negative, and variable rates of change. Although rates of change have accelerated, there were many locations with a consistent neutral rate of change in cover. High positive rates of change frequently preceded high invasive annual grass cover, and locations that had low cover rarely had a history of high positive rates of change.
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  We identified potential management opportunities by combining rates of change in cover and percent cover data, illustrating both invasion severity and trajectory. We applied these potential opportunities to a map of the sagebrush biome using example thresholds. This map identifies locations that could be prioritized for different management goals and shows how those areas align with the Sagebrush Conservation Design management framework.