PS 11-163 - Changes in the soil microbiome due to kudzu invasion inhibit growth of a native legume

Abstract: Invasive plant species represent a major threat to native ecosystems. They reduce native biodiversity, disrupt nutrient cycles, habitat structure, food webs and microbial communities above- and belowground. Kudzu (Pueraria montana var. lobata) is one of the fastest growing and most noxious invasive plants in the US. As a legume, it has a strong influence not only on carbon and nitrogen dynamics but likely also on the composition of soil microbial communities. Recent studies suggest that alterations to the soil microbial community can hinder the establishment of desired native plant species that often require specific soil microorganisms such as mutualistic mycorrhizal fungi, rhizobia, and other endophytic bacteria for successful establishment. The goals of our study are to assess 1) how the soil microbiome associated with kudzu affects growth of a native legume, and 2) differences in the soil microbiome between the invasive legume, kudzu and a native legume, Chamaecrista fasciculata.

We performed a greenhouse study in which we grew the native legume and kudzu as individual seedlings in sterile soil inoculated with soil microbes collected from a kudzu invaded area or an adjacent uninvaded area. Our results show that kudzu creates positive feedbacks via changes in the soil microbial communities that might further foster its invasion success. Soil microbes associated with kudzu suppressed the growth of the native legume Chamaecrista fasciculata but were beneficial for kudzu itself. However, we do not know the identity of the microbes causing these drastic growth effects, limiting our ability to apply soil inoculations to increase restoration success. To address this issue, we extracted soil DNA from the above-mentioned greenhouse experiment. Using these DNA samples, we amplified four target regions using PCR. Each of these target regions is used to identify operational taxonomic units (OTUs) for a target group of microbes. Upon receiving results from our sequencing, we will analyze the data to sort sequences from soil samples into OTUs; and test whether the soil microbial communities from the invaded vs. uninvaded soil are distinct from one another.

Our results indicate that kudzu invasion inhibits the growth of the native legume via plant-soil microbial interactions. Applying active intervention strategies that reverse soil microbial changes seem critical for the restoration of kudzu-invaded ecosystems.