Targeted Grazing by Sheep to Manage Cheatgrass in Idaho's Rangelands

Cheatgrass ( Bromus tectorum ) invasion increases wildfire risk and negatively impacts sagebrush ecosystems and rangeland-based agricultural production. In sagebrush ecosystems, diverse native plant communities tend to be more resistant to invasion and resilient to disturbances, like wildfire. Grazing has been suggested as a tool to combat cheatgrass and thus promote more resilient vegetation communities. However, most cheatgrass targeted grazing research has been done with cattle, and studies with sheep remain sparse. Here, we introduce a new, transdisciplinary project that aims to answer the question of how sheep can be used to reduce cheatgrass and wildfire risk, while also examining the economic costs and benefits of this practice. In the summer of 2022, our team of researchers, land managers, and sheep producers established a sheep targeted grazing experiment at a management-relevant scale on the Sawtooth National Forest, Idaho. Our grazing treatments will compare dormant-season grazing in spring and fall, when cheatgrass is growing but most perennial species are not, to “traditional” summer grazing. Treatment areas are nested within two allotments grazed by 800-1200 ewes and their lambs. Despite the treatment plots’ relatively high elevation (> 1800 m), our baseline measurements indicate that, on average, cheatgrass comprises 63% of the vegetation cover.  Starting from this baseline, we will assess grazing treatment effects on the composition of aboveground vegetation and fuel loads. We will also examine soil processes, and particularly nitrogen availability, to enhance understanding of the ecological mechanisms underpinning our results. Fire behavior models and economic models will estimate the financial and societal costs and benefits of adopting sheep targeted grazing practices to manage cheatgrass invasion and wildfire risk. Finally, our outreach to diverse audiences will build knowledge and shared understanding of the potential for using sheep as a management tool to tackle pressing environmental challenges on western rangelands.