Publication Date
8-1-2025
Date of Final Oral Examination (Defense)
5-19-2025
Type of Culminating Activity
Thesis
Degree Title
Master of Environmental Management
Department
School of Public Service
Supervisory Committee Chair
Kelly A. Hopping, Ph.D.
Supervisory Committee Member
April Hulet, Ph.D.
Supervisory Committee Member
Kerry M. Byrne, Ph.D.
Supervisory Committee Member
Allison Simler-Williamson, Ph.D.
Abstract
Invasive annual grasses like cheatgrass (Bromus tectorum) are transforming fire regimes, reducing native biodiversity, and threatening the livelihoods of rural communities across sagebrush rangelands. Landscape-scale management efforts for invasive grasses have had limited success, highlighting the need for innovative management solutions tailored to the needs of the landscape that incorporate ecological, economic, and social considerations. This study evaluates the effects of sheep targeted grazing on plant community dynamics and cheatgrass cover in higher elevation sagebrush ecosystems. We implemented spring, fall, and combined fall and spring targeted grazing treatments over two years, assessing their impacts on species diversity (alpha diversity) and community composition (beta diversity). Additionally, we investigated how sheep may be driving changes in vegetation based on their selection preferences, as identified by sheep herders. Spring grazing led to the greatest reductions in species diversity while also reducing cheatgrass. In contrast, fall grazing alone reduced cheatgrass more effectively than any other treatment without significantly altering diversity metrics, suggesting it may have fewer ecological tradeoffs as a management strategy in these systems. Combined spring and fall grazing treatments lowered cheatgrass cover in the first year but produced variable effects on species diversity and reduced the cover of sheep’s highly preferred forage species. Assessing sheep impacts based on dietary preferences rather than plant growth form provided insights into grazing effects. Using this approach revealed that sheep reduced cheatgrass cover despite it not being a preferred forage species, suggesting that non-consumptive mechanisms may be contributing to the observed reduction in cheatgrass. This underscores the utility of incorporating herders’ local knowledge to refine grazing management in higher elevation rangelands with diverse plant communities. Ultimately, these findings offer insights for improving targeted grazing strategies that balance invasive species control with native biodiversity conservation.
DOI
https://doi.org/10.18122/td.2435.boisestate
Recommended Citation
Walter, Kloe R., "Evaluating Vegetation Dynamics Under Sheep Targeted Grazing in Mountain Big Sagebrush Rangelands" (2025). Boise State University Theses and Dissertations. 2435.
https://doi.org/10.18122/td.2435.boisestate