Date of Award

Spring 2019

Project Type

Dissertation

Program or Major

Natural Resources

Degree Name

Doctor of Philosophy

First Advisor

Serita D Frey

Second Advisor

Kristina A Stinson

Third Advisor

Richard G Smith

Abstract

Non-native, invasive plants can fundamentally alter soil fungal communities and edaphic properties. In this dissertation, I first measured fungal and edaphic responses and recovery to invasive, Alliaria petiolata (garlic mustard; Brassicaceae) eradication across Southern New England. I conducted an experimental eradication and tracked fungal communities and soil properties for three years in relation to reference uninvaded plots and actively invaded plots. Neither the fungal community nor soil properties recovered (i.e. became similar to reference uninvaded plots) following eradication, and I discuss how altered soil properties likely prevented fungal communities from recovering via environmental filtering. I also measured fungal and edaphic responses to the impacts of an experimental garlic mustard invasion in a long-term soil warming and simulated nitrogen deposition experiment. I found that soil warming had the strongest impact on fungal communities and warming interacted with invasion to amplify the impacts of invasion on fungal biomass and community composition. Garlic mustard, like all Brassicaceae, is non-mycorrhizal, and I characterized a mechanism that maintains the non-mycorrhizal status of these plants in a greenhouse study. The Brassicaceae produce secondary chemicals (glucosinolates) that deter herbivores and suppress plant pathogens, and I tested whether these chemicals also prevent mycorrhizal fungi from colonizing Brassicaceae roots. I found that removing these chemicals from Arabidopsis thaliana, a related species to garlic mustard, increased mycorrhizal fungal colonization and suppressed plant performance in soils with mycorrhizal fungal inoculation, while mycorrhizal fungi did not affect plants that could produce these chemicals. Lastly, I re-analyzed publicly available fungal community data and mapped where across the globe fungi assemble in relation to different environmental conditions (i.e. floral, climatic, edaphic) versus dispersal and drift. Since extensive variation in fungal community composition cannot be explained by environmental variables in studies across the globe, I assessed whether certain regions of the world are more likely to structure fungal communities via niche or neutral processes. I found that in northern latitude forests and arctic tundra, fungal assembly was primarily due to niche processes. In most of the other plots across the globe fungal assembly was primarily stochastic and indicative of chronic dispersal and recruitment limitations. Together, the four studies in this dissertation offer new insight explaining how global change stressors and environmental filters affect fungal community composition.

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