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January 7, 2025

The continued proliferation of invasive annual grasses could re-shape ecosystems by diminishing native vegetation and increasing the spread and consequences of wildland fires. This manuscript describes rates of change in invasive annual grass cover from 1987–2021, and the ways in which rates of change in cover can be used to inform invasive annual grass management in sagebrush ecosystems.

a triangle filled with color gradient (blue, red, yellow in each corner). Text and arrows along gradients.
Figure 1. Decision triangle for potential management actions. The “protect” category, where rates of change in invasive annual grass cover are negative or neutral and invasive annual grass cover is low, could include activities such as monitoring, early detection and rapid response (EDRR), and preventing additional disturbance. Strategies in the “treat” category, where rates of change are positive, but percent cover is low/moderate, could include treatment with herbicides, restoration actions, and EDRR where cover is low. In areas with a hypothesized “contain” strategy, when rates of change are high positive and invasive annual grass cover is high, management goals could include isolation, prevention of spread, and protection from fire transmission. Importantly, thresholds and actions can be flexible and can be adjusted to balance local invasion context and management goals. From Roche and others (2024).
 
Invasive grasses are proliferating rapidly across the sagebrush biome. Where prevalent, annual invasive grass species like cheatgrass increase fire risk and intensity, and alter critical functions of ecosystems like nutrient cycling. Managers of invasive plants have limited time and funding to fight invasives across the entire sagebrush biome, and thus, need tools that can support decisions regarding where and when to implement specific management actions.
 
In this study, authors used vegetation cover data from 1987-2021 to measure yearly invasive annual grass cover and rates of change in invasive annual grass cover across the sagebrush biome. They found that rates have accelerated over time but were highly variable across the biome. 
 
The authors also identified and mapped potential invasive annual grass management opportunities across the sagebrush biome given invasive annual grass percent cover and rates of change in cover. The associated decision triangle (Figure 1) and map (Figure 2) can assist managers in identifying areas in need of different types of management action.
 
Full Citation: Roche, M.D., Crist, M.R., Aldridge, C.L., Sofaer, H.R., Jarnevich, C.S., Heinrichs, J.A., 2024, Rates of change in invasive annual grass cover to inform management actions in sagebrush ecosystems: Rangelands, https://doi.org/10.1016/j.rala.2024.10.001

 
map of sagebrush biome with four colors dotting the geographic area. Two inset maps show close-ups of the bigger map.
Figure 2. Potential management opportunities derived from a combination of mean rates of change in cover and mean invasive annual grass cover in 2017–2021. Red indicates locations with very high rates of change or very high invasive annual grass cover, which may not have favorable treatment outcomes. Yellow indicates locations where the combination of rate of change and invasive annual grass cover may be amenable to treating invasive annual grasses. Blue shows areas with very light invasions or where rates of change are negative, and thus, protecting these locations by resisting additional disturbance and continuing to monitor these locations for changes in an undesirable direction could be an appropriate approach. Management goals in areas with variable rates of change (gray) will depend on the ecological context and local knowledge. Insets show details for two example locations. From Roche and others (2024).

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