Current and projected changes in climate will create novel environments in the arid and semi-arid western US. Native and non-native species alike will respond to these changes, and we can expect contraction of suitable habitat for species in some areas and expansion in others. Locations where conditions become less suitable for exotic brome-grasses could provide opportunities to restore native plant communities and ecosystem function. Or they could be at risk of invasion by other undesirable species. These opportunities and challenges will vary greatly over space and time across the western US. Uncertainty about and variation in weather will remain an obstacle to success of restoration efforts, but will not hamper the success of exotic brome-grasses. Prescriptive management is unlikely to succeed under such conditions. We need to build upon what we have learned from past efforts to manage exotic brome-grasses and utilize management frameworks that are flexible enough to handle new environmental conditions and great uncertainty. In this spirit, we identified 45 peer-reviewed articles in which Bromus tectorum L. (cheatgrass or downy brome) had been controlled using burning, defoliation, herbicide application, and/or revegetation. We analyzed effect sizes for B. tectorum percentage cover and biomass in treated and untreated controls.
Results/Conclusions
Where exotic brome-grasses have invaded, their management must be included in restoration plans. Restoration is a long term ecological, iterative process, well-suited to an adaptive management framework. Evaluating the effects of management actions, as accomplished by our literature review, is an essential element of adaptive management. We found that burning used to control B. tectorum decreased its percentage cover in the short-term, but not the longer-term, and its biomass was increased by burning in both time frames. Defoliation by grazing or mowing reduced B. tectorum biomass for up to 2 years and percentage cover for 1 year. Only herbicide application consistently reduced both short- and longer-term B. tectorum percentage cover and biomass. Seeding reduced B. tectorum biomass production, but its effects on B. tectorum cover were variable, especially in the long term. Effective integration of monitoring results within an adaptive management framework may require numerous iterations combined with parallel studies to identify effective restoration species and make adjustments for unanticipated environmental conditions. Adaptive management has been used successfully by public agencies to manage exotic brome-grass invaded systems. These research results and management accomplishments will provide the foundation for successful management of novel, brome-grass invaded systems in the future.