Date of Award

Winter 2015

Project Type


Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Serita D Frey

Second Advisor

Linda T van Diepen

Third Advisor

Stuart A Grandy


Non-native invasive plants can disrupt native plant communities and soil function (e.g., C and N cycling), but few studies have examined how soil microbial community structure differs in association with invasion. This work focused on Alliaria petiolata (garlic mustard), a non-mycorrhizal Brassicaceae that can displace native plants and reduce aboveground diversity. Garlic mustard produces toxic phytochemicals that can suppress mycorrhizal fungi, but we currently do not know if garlic mustard invasion affects the general fungal community, including specific mycorrhizal fungi, saprotrophic fungi, and plant pathogens and parasites. The objective of this work was to compare uninvaded and invaded soils from deciduous forest understories in the Northeastern U.S. in terms of fungal community structure, edaphic soil properties, and the correlation between these variables and garlic mustard abundances in the invaded plots. We show that garlic mustard invasion was associated with dramatic differences in fungal diversity, with a particular increase in saprotrophic fungal diversity. Saprotrophic diversity was positively correlated with the relative abundance of garlic mustard in invaded plots. In terms of edaphic soil properties, invaded soils also possessed reduced C:N ratio relative to uninvaded soils due to lower organic C concentrations in invaded soils. C:N ratio was negatively correlated with the fungal community through direct changes in saprotrophic fungal relative abundance and the ratio of saprotrophic fungi to ectomycorrhizal fungi. Invasion was also associated with higher relative abundance and diversity of plant pathogens and parasites, including the occurrence of novel pathogens, such as Olpidium brassicae, a fungus that transmits necroviruses infectious to herbaceous plants. In summary, invasion was associated with fundamentally different soil fungal communities and this was correlated with altered edaphic soil properties and the abundance of garlic mustard across the invaded landscape.