Opposing effects of soil biota on a native plant shoot and root growth in the presence of a invasive competitor

Abstract Aims: Soil biota can affect native and alien species differently, and consequentially promote or suppress alien species invasion. However, how soil biota influence the competition between native and alien species has rarely been explored. Methods: Here, our study tested how the rhizosphere biota of the invasive plant Alternanthera philoxeroides and its native congener A. sessile in China affected their competition with a greenhouse experiment. Results: We found that soil biota, regardless from the rhizosphere of the native or the invasive plant, increased native plant total and shoot mass in the presence of the invasive plant but not in the presence of conspecific individual. Furthermore, soil biota from its own rhizosphere soils decreased native plant root mass in the presence of the invasive plant. Therefore, the native plant accumulated more shoot and total mass, but less root mass than the invasive plant only in the presence of soil biota. Conclusions: Overall, our results highlight the importance of exploring the roles of soil biota in plant competition within a whole plant framework.