Publication Date


Date of Final Oral Examination (Defense)


Type of Culminating Activity


Degree Title

Master of Science in Biology



Major Advisor

Nancy Glenn, Ph.D.


Stephen Novak, Ph.D.


Marie-Anne de Graaff, Ph.D.


Dryland ecosystems are globally distributed and occupy nearly half of Earth’s terrestrial surface. Drylands are particularly vulnerable to degradation and their restoration has become a global concern. Sagebrush-steppe ecosystems in the intermountain western United States have been subject to decades of active management efforts to address invasive species and restore plant communities, and can serve as a relevant case study to investigate dynamics between fire, invasive species, and management treatments in a representative dryland system. My objective was to determine the relative importance of fire history, management treatment history, abiotic, and biotic factors in relation to the abundance of key vegetative components in the Morley Nelson Snake River Birds of Prey National Conservation Area, a highly fire-prone and endangered sagebrush-steppe ecosystem. The vegetative components of interest included the non-native annual grass cheatgrass (Bromus tectorum), the native perennial bunchgrass Sandberg bluegrass (Poa secunda), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), and biological soil crust. I performed multivariate model selection for each response variable in burned and unburned study areas.

My results indicate that within both burned and unburned areas, B. tectorum abundance was negatively associated with P. secunda and biological soil crust, highlighting the potential of shallow-rooted perennial grasses and soil crust to limit the abundance of B. tectorum. Post-fire management treatments were not included in best fit models for B. tectorum abundance, confirming the findings of previous work on the limited success of post-fire treatments in warm and dry regions of the sagebrush-steppe ecosystem. A. tridentata ssp. wyomingensis exhibited a negative relationship with the distance to the nearest fire border in unburned areas, suggesting the role that fire edge effects may play in landscapes with unburned sagebrush. P. secunda appears to tolerate some level of fire, withstanding up to two repeat fire events. Conversely, B. tectorum reaches its highest abundance after three or more fires. Repeat fire is a significant threat to Wyoming big sagebrush-communities, but our results suggest that burned landscapes that still contain P. secunda and biological soil crust offer opportunities to explore the dynamics between B. tectorum and P. secunda and the restoration potential of P. secunda.


Available for download on Sunday, December 15, 2019

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