Fungal communities do not recover after removing invasive Alliaria petiolata (garlic mustard)

The negative impacts of non-native invasive plants on native plants has prompted intensive eradication efforts, but whether eradication can restore soil microbial communities that are also sensitive to invasion is generally not considered. Some invasive plants, like Alliaria petiolata (garlic mustard), specifically alter soils in ways that promote the invasion process. Garlic mustard disrupts mycorrhizas, increases fungal pathogen loads, and elevates soil nutrient availability and soil pH; thus, the fungal community and soil property responses to garlic mustard eradication may be key to restoring ecosystem function in invaded forests. We conducted a garlic mustard eradication experiment at eight temperate, deciduous forests. 1 and 3 years after initiating annual garlic mustard removal (hand pulling), we collected soil samples and characterized fungal community structure using DNA metabarcoding alongside a suite of edaphic properties. We found that fungal richness, the number of shared fungal species, fungal biomass, and the relative abundance of fungal guilds became less similar to invaded plots by year three of eradication and more similar to uninvaded reference plots. However, fungal community composition did not resemble uninvaded communities by the third year of eradication and remained comparable to invaded communities. Soil chemical and physical properties also remained similar to invaded conditions. Overall soil abiotic-biotic restoration was not observed after 3 years of garlic mustard removal. Garlic mustard eradications may therefore not achieve management goals until soil physical, chemical, and biological properties become more similar to uninvaded forested areas or at least more dissimilar to invaded conditions that can promote invasion.