Successful invasion by exotic plant species can modify the abundance and composition of soil microbial communities. Previous studies regarding invasive plants’ effects on soil microbial biomass are inconsistent; with some studies finding increased microbial biomass, no significant change, and others reporting reduced microbial biomass. However, little is known about their effects on soil microorganisms.

   Dr. Xiao Haifeng and his colleagues of Xishuangbanna Tropical Botanical Garden (XTBG) used two invasive (Eupatorium adenophora and Chromolaena odorata) and two native plant species (Eupatorium japonicum and Eupatorium heterophyllum) to compare the soil feedback (on plant growth) before and after soil sterilization and from plant-root exudates. They also examined bacterial and fungal biomass and community composition.

Their objectives were (1) to test the hypothesis whether invasive and native plants have different effects on bacterial and fungal community, (2) to detect feedbacks of soil organisms on invasive and native plant species, and (3) to further explore belowground microbiological mechanisms behind successful invasions by E. adenophora and C. odorata.

In their investigation of alteration of soil microbial communities by invasive species (E. adenophora and C. odorata) and native species (E. japonicum and E. heterophyllum), they found that the soil fungal community was altered more than was the bacterial community. Invasive species C. odorata led to higher fungal biomass than did other plant species. Different response patterns of bacterial and fungal communities were observed. No significant difference was observed in bacterial biomass and community composition among four plant species. However, fungal biomass was higher in the soil with C. odorata and there were significant differences in soil fungal community composition among these four plant species.

 Higher abundance of particular arbuscular mycorrhizal fungi species such as Paraglomus sp. in soil modified by C. odorata may be one of the mechanisms contributing to its success as an invasive plant species.

 The study entitled “Soil fungi rather than bacteria were modified by invasive plants, and that benefited invasive plant growth” has been published online in Plant and Soil.