Abstract

Understanding how humans modify their environment and what are these impacts of these modifications on plant-associated microbiomes is critical to improving management of human-managed areas, such as green spaces or natural areas. Such knowledge of how plants and their associated microbiomes respond to human modifications to the environment can inform land management and restoration efforts to maintain ecosystem services provided by these organisms. The overarching questions of this dissertation are centered on (1) how human activities alter abiotic and biotic characteristics of soil, and (2) what the consequences of those changes are for plant-associated microbiomes. Chapter 1 provides a general overview of how humans modify the landscape through urbanization and management of invasive plant species. In Chapter 1, I also explain the significance of microbial communities, or microbiomes, in these contexts of urbanization and management of invasive plant species. In Chapter 2, I conducted an observational study to examine how soil abiotic (i.e., soil chemistry) and biotic (e.g., microbiomes) properties vary along an urbanization gradient. With Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Mass Spectrometry (ICP-MS), I measured the macroelements and trace and heavy metals in soils along an urbanization gradient. I found that soil chemistry does vary along an urbanization with heavy metals being relatively higher in urban sites. Using 16S rRNA and ITS metabarcoding, I characterized the bacterial and fungal communities of the soil and found that these soil microbial communities do differ between site types. I also observed that soil chemistry did correlate with both the bacterial and fungal soil communities. The results from Chapter 2 improve our understanding of what factors shape the diversity and composition of soil microbiomes across an urbanization gradient. In Chapters 3 and 4, I conducted an experimental field study in an Amur honeysuckle-invaded woodland at the Missouri Botanical Garden’s Shaw Nature Reserve. I established five experimental blocks in a split-plot random design with prescribed burn applied at the main plot level and Amur honeysuckle removal at the subplot level. In Chapter 3, I examined how the management practices of prescribed burn and/or manual removal alter the aboveground vegetation, soil chemistry, and the bulk soil microbial communities in this woodland. We found that manual removal and the combined treatment of prescribed burn and manual removal did reduce the abundance of Amur honeysuckle shrubs and other non-native shrubs. However, the combination of manual removal and prescribed burn was marginally significant in the reduction of Amur honeysuckle seedlings. As for the soil chemistry, the total carbon, total nitrogen, and C:N ratio all decreased from year 1 and year 2, but were unrelated to the treatments. For the composition of the bacterial and fungal communities, we found a similar effect of year, but no effect of treatments. The results from Chapter 3 give us better insight into the efficacy of current invasive plant species management strategies and their impacts on the chemical and microbial composition of soils. In Chapter 4, I compared Amur honeysuckle-associated microbiomes across the compartments of bulk soil, rhizosphere soil, and roots, and how the treatment of prescribed burn may impact the microbiomes of these compartments. When comparing the bacterial and fungal communities of these compartments, there was a significant effect of year, but no significant effect of year and treatment. However, there was a significant effect of sample type, indicating that the compartments do differ between one another in alpha and beta diversity. The root microbiome had the lowest bacterial alpha diversity compared to the bulk soil and rhizosphere microbiomes. Bacterial and fungal community composition was similar between the bulk soil and rhizosphere communities while the root microbiome had a more distinct community composition. At the phylum and family levels, we detected bacterial and fungal taxa that were differentially abundant between the compartments. Chapter 4 improves our understanding of the microbial communities associated with an invasive plant species and how management practices may or may not impact such communities. In Chapter 5, I conclude my dissertation with a summary of my projects and discuss future directions. Together, this dissertation incorporates community and microbial ecology to understand how plants and their associated microbiomes respond to changes in the environment caused by humans. Such understanding has the potential to better inform restoration and management efforts of human-managed areas.

Committee Chair

Rachel Penczykowski

Committee Members

Christine Edwards; Elizabeth Mallott; Jeffrey Catalano; Joan Strassmann; Matthew Albrecht

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Evolution, Ecology & Population Biology)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

4-28-2026

Language

English (en)

Author's ORCID

https://orcid.org/0000-0002-6892-7940

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Available for download on Thursday, April 27, 2028

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