Invasive Grass Dynamics in Sagebrush Ecosystems

The invasion of annual grasses, particularly exotic species such as cheatgrass, into sagebrush ecosystems has triggered fundamental shifts in community structure, fire regimes and ecosystem services. Once dominated by diverse perennial shrubs and forbs, these landscapes are increasingly transitioning to grass-dominated states that sustain frequent, high-intensity wildfires. This dynamic arises from a positive feedback loop: annual grasses produce fine, continuous fuels that ignite readily and carry fire across vast areas, creating conditions unsuitable for shrub recovery. Consequently, sagebrush recruitment falters, biodiversity declines and grazing resources diminish. Climate warming and altered precipitation patterns further exacerbate these changes by favouring invasive herbs over deep-rooted natives. Restoration is hindered by erratic establishment success, while management strategies must balance prevention, rapid post-fire interventions and long-term resilience building. Understanding the spatial heterogeneity of vulnerability, fuel accumulation processes and thresholds of shift between states is central to conserving ecosystem functions and cultural values linked to sagebrush landscapes globally.

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Invasive Grass Dynamics in Sagebrush Ecosystems publication trend

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Technical terms

Sagebrush steppe: Semi-arid shrubland dominated by Artemisia species and perennial grasses.

Cheatgrass: An invasive annual grass (Bromus tectorum) that accelerates fire frequency.

Fine fuels: Lightweight plant material such as grass litter that dries quickly and fuels wildfires.

Alternative stable states: Mutually exclusive community configurations maintained by reinforcing feedbacks.

Resilience: The ability of an ecosystem to recover structure and function after disturbance.

Resistance: The capacity of a system to prevent invasive establishment or withstand stress without shifting states.

References

1. Ecological restoration in the age of apocalypse. Global Change Biology (2023).
2. Refining the cheatgrass–fire cycle in the Great Basin: Precipitation timing and fine fuel composition predict wildfire trends. Ecology and Evolution (2017).
3. The elevational ascent and spread of exotic annual grass dominance in the Great Basin, USA. Diversity and Distributions (2021).
4. Operationalizing Resilience and Resistance Concepts to Address Invasive Grass-Fire Cycles. Frontiers in Ecology and Evolution (2019).