Publication Date

8-2025

Date of Final Oral Examination (Defense)

5-22-2025

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biological Sciences

Supervisory Committee Chair

Allison Simler-Williamson, Ph.D.

Supervisory Committee Member

Toby Maxwell, Ph.D.

Supervisory Committee Member

Leonora Bittleston, Ph.D.

Abstract

Plant community compositional and functional responses to natural disturbance can be described through metrics of resistance and resilience. In heavily invaded plant communities, restoration techniques such as herbicide application or mowing can be understood as management-based disturbances that aim to shift communities toward native composition or pre-invasion functions. In this case, highly resistant or resilient invasive assemblages can cause restoration efforts to fail. There is a need to better understand the drivers of this “resistance and resilience to restoration” for both univariate functions and community composition. Further, there is a need to identify whether drivers of resistance and resilience to disturbance are similar in invaded and native communities. In this work, we assess the role of soil resource fluctuations, pre-disturbance biodiversity, and species dominance in determining the resilience and resistance of “diversely invaded” plant communities, using a four-year study of 130 plots following herbicide treatments in a degraded sagebrush steppe ecosystem. To evaluate our hypotheses, we quantified community stability in two ways – using single state variables (e.g., biomass) in a generalized linear mixed modeling framework, as well as trajectories of community composition using community trajectory analysis.

Preliminary findings suggested that stability metrics for invasive biomass increased with soil nitrogen availability and with pre-treatment invasive diversity, but these drivers were weaker for native biomass responses. The dominance of particular invasive species also increased the stability of composition and invasive biomass, while inhibiting native stability. At the community scale, resistance and resilience increased with pretreatment invasive cover but decreased with the availability of soil nitrogen, whereas total community recovery decreased with native diversity and increased with post-disturbance pulses of soil nitrogen. These preliminary results help advance our understanding of how: 1) invasive and native-dominated communities differ in their resilience and resistance to disturbances; and 2) responses to disturbance differ for univariate and multivariate descriptors. Understanding the drivers of “resistance and resilience to restoration” could help managers prioritize limited resources.

DOI

https://doi.org/10.18122/td.2402.boisestate

Available for download on Sunday, August 01, 2027

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