Graduation Date

Summer 2021

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources: option Environmental Science and Management

Committee Chair Name

Dr. Kerry Byrne

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Erik Jules

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. Harold Zald

Third Committee Member Affiliation

Community Member or Outside Professional

Subject Categories

Environmental Science and Management

Abstract

Soil seed banks are critical biodiversity repositories for many dryland plant communities. Understanding how environmental factors alter seed bank composition can provide valuable information on ecological processes within a community and be useful for creating land management strategies. Using the seedling emergence method, I characterized the seed bank of two adjacent dryland plant communities that vary in dominant sagebrush species, structure, and function. Specifically, within an Artemisia arbuscula dominated community and Artemisia cana dominated community, I assessed the influence of three environmental factors on each seed bank: experimentally imposed drought, shrub microsites (compared to interspaces), and aboveground vegetation. Within the A. arbuscula community, drought decreased seed species diversity, seed species evenness, and exotic forb seed density, and increased exotic grass seed density. Total seed density, native forb seed density, and seed species diversity was greater in shrub microsites compared to interspaces. Within the A. cana community, drought only decreased exotic forb seed density and there were no microsite effects. Bray-Curtis index showed low similarity (A. arbuscula dominated plant communities (with large expanses of bareground) may experience more drought induced impacts than adjacent sagebrush communities. Additionally, while native annual forb seeds may remain resilient during drought, changing climatic regimes could concurrently promote an increase in propagule pressure of invasive annual grasses such as Ventenata dubia (ventenata). My study also highlights the role of shrub canopies as beneficial microsites for seeds, especially in preserving seed bank diversity and native forb seed density within A. arbuscula dominated plant communities.

Citation Style

APA

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