Soil microbial communities are not altered by garlic mustard in recently invaded central Illinois forests

Abstract

The invasive forest plant garlic mustard (Alliaria petiolata) has been shown to alter soil microbial communities in the northeastern part of its invaded range in the United States, and this disruption of soil communities may contribute to its invasion success. However, garlic mustard allelochemistry can vary with invasion age, and it is not clear whether garlic mustard's impacts on soil microbes are consistent over its invaded range. Here, we compare the composition and diversity of soil fungal, bacterial, and archaeal communities among garlic mustard present, absent, and removed treatments in replicated blocks across five forests in the midwestern United States with relatively young garlic mustard invasions (approximately 17-26 years old, with consistent management). We collected samples in May and August, corresponding to garlic mustard active and senescent life history stages. While soil fungal and bacterial/ archaeal communities (based on ITS2 region and 16S rRNA gene DNA sequencing, respectively) differed significantly between different blocks/forests and over time, we found no significant effect of garlic mustard treatment on soil microbial community composition or the relative abundance of mycorrhizal, saprotrophic, or pathogenic fungal guilds. The lack of garlic mustard impacts on the soil microbial community in recently invaded central Illinois forests suggests that these well-documented impacts in the northeastern United States and in older invasions cannot necessarily be generalized across all environmental contexts.

Accelerated gross nitrogen cycling following garlic mustard invasion is linked with abiotic and biotic changes to soils

“…Correlations between microbial community composition and gross N cycling rates support the hypothesis that garlic mustard alters N cycling by modifying the soil microbiome. Fungal and bacterial/archaeal communities in these forests differed among garlic mustard treatments, despite previous findings from similar sites to the contrary (Edwards et al, 2022), showing the microbial impact of garlic mustard can change over time (Lankau, 2011). Further, garlic mustard disrupted soil microbial community composition and homogenized fungal communities, though we found no evidence for direct effects on fungal guilds or microbial diversity.…”

“…Garlic mustard (Alliaria petiolata (Bieb.) Cavara & Grande), a prominent invasive understory herb in North American forests, can alter soil properties (Anderson and Kelley, 1995;Morris et al, 2012), soil microbiomes (Stinson et al, 2006;Wolfe et al, 2008;Anthony et al, 2017;Duchesneau et al, 2021; but see Edwards et al, 2022), and the nutrient stoichiometry of soil organic matter (Rodgers et al, 2008a;Burke et al, 2011). Garlic mustard is a biennial plant native to western Europe, first introduced to the eastern United States in 1860, which now is found in over 80% of US states and half of the Canadian provinces (Rodgers et al, 2022).…”

Invasion by the annual grass, Ventenata dubia does not impact mycorrhizal fungal abundance in an endangered prairie

“…We found no record of when V. dubia first entered each site, and they may have had different invasion timelines. Given that longer periods of invasion are more likely to negatively impact AM fungi than shorter periods of invasion (Edwards et al 2022), if Kamiak and Smoot Hill plots are in earlier stages of invasion than Steptoe Butte, then V. dubia impacts may not be measurable yet. In any case, the lack of a consistent response to V. dubia levels suggests that AM fungal propagules are not directly repressed by V. dubia .…”