Abstract: As invasive plants decrease biodiversity and cause substantial economic losses, finding effective ways to control plant invasions is urgently needed. Parasitic plants may offer a potential means of controlling plant invasions. However, how the litter produced by parasitic plants regulates plant invasions remains unclear. In this study, five pairs of congeneric invasive and native plants were grown under two parasitic litter addition treatments (with vs. without litter), two soil microbe treatments (with vs. without microbes) and two competition conditions (with vs. without competition). The results showed that, in the presence of soil microbes, parasitic litter had an inhibitory effect on invasive plants, especially when competed with native species. Additionally, parasitic litter significantly altered the compositions of the soil bacterial and fungal communities, and had a stronger negative effect on fungal diversity in soil grown with invasive plants than in soil grown with native plants. Parasitic litter also significantly suppressed the growth of beneficial fungal group arbuscular mycorrhizal fungi. Moreover, the response of invasive plants to parasitic litter addition was significantly related to the relative abundance of the dominant phyla Pseudomonadota and Bacillota. Fungal diversity was positively associated with plant growth responses to parasitic litter addition. Our results provide an illustrative case for understanding how parasitic litter regulates plant invasion. Our results also indicate that parasitic litter may serve as an effective biological control agent for plant invasion.

Key words: biological control, competition, Cuscuta, parasitic litter, plant invasion, soil microbes