Agronomy and Horticulture Department


First Advisor

Dirac Twidwell

Date of this Version

Fall 12-2023


A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agronomy

Under the supervision of Professor Dirac Twidwell

Lincoln, Nebraska, December 2023


Copyright 2023, Robert Peterson


Woody plant encroachment is a global threat and has been transitioning grasslands to woody dominance at a biome scale. This threat is present in the Great Plains grassland biome which is currently experiencing grassland biome collapse as the alternative woody biome advances northwest. Nebraska, which contains the most intact temperate grassland in the world, is currently at the front lines of this large-scale transition making this state’s management decisions vital for the remaining grasslands and the species which rely on these ecosystems. In this study, we assess the vulnerability of Greater Prairie Chicken and Tier 1 at-risk species in Nebraska caused by the threat of grassland transition to woody dominance. Chapter one focuses on the threat of the advancing woody biome to Greater Prairie Chicken in Nebraska, utilizing two measurements to quantify risk. Chapter two utilizes participatory Tier 1 at-risk species assessments to assess statewide and regional vulnerability to Tier 1 species listed in Nebraska’s Natural Legacy project caused by the threat of grassland lost to woody dominance. Overall, the findings show that Greater Prairie Chicken, and key at-risk species found in Nebraska have become increasingly vulnerable to this threat. These results highlight the need for adaptive management strategies to mitigate the risk of woody encroachment and subsequent grassland transition to woody dominance.

Advisor: Dirac Twidwell