Garlic mustard (Alliaria petiolata) Invasion Reshapes Soil Microbial Communities and Network Structures in South Korea

Abstract

Garlic mustard (Alliaria petiolata ) is a recently introduced invasive species in South Korea, yet its ecological impacts remain unclear. We assessed how garlic mustard invasion modifies soil microbial communities and chemical properties as part of potential plant-soil feedback mechanisms. Soil samples were collected from invaded and adjacent uninvaded sites within three regions―Samcheok, Suwon, and Incheon―where garlic mustard has been reported. We analyzed soil bacterial and fungal communities and measured water-soluble ion concentrations to evaluate associated biotic and abiotic changes. Microbial diversity was significantly altered by invasion across all sites, but functional shifts in microbial communities were observed only at the Samcheok sites. Specifically, the abundance of chemoheterotrophic bacteria increased, while phototrophic and nitrogen-fixing groups declined. Fungal communities in Samcheok also exhibited a decrease in ectomycorrhizal fungi and an increase in pathogenic fungi. Constrained ordination (db-RDA and CCA) revealed that Samcheok was the only region where microbial communities were strongly correlated with soil chemistry. pH emerged as a key driver of both bacterial and fungal communities, with NH4+ and NO3- further contributing to the differentiation between invaded and uninvaded bacterial communities. These patterns suggest that altered nitrogen availability and acidity may underlie the compositional and functional changes observed in this region. Based on the 100 most abundant taxa, network analysis consistently showed greater connectivity and density in bacterial communities of invaded soils across all regions, indicating enhanced structural stability. In contrast, the fungal network remained unchanged. These findings suggest that garlic mustard invasion alters microbial community structure and interactions, with consistent shifts in bacterial network structure and region-specific environmental associations, possibly reflecting differences in invasion stage. Acknowledgements : This work was supported by the National Research Foundation of Korea grant funded by the Korea government (Ministry of Science and ICT) (No. NRF-RS-2024-00456189).