Temporal changes in plant–soil feedbacks between the invasive Phytolacca americana and congeneric native and non‐invasive alien plants

Abstract

The direction and intensity of plant–soil feedbacks (PSFs) and the reciprocal effects between plants and soils can change over time. PSFs can also affect competition between invasive and native plants. However, most PSF research is conducted in simple experimental settings where temporal changes are not considered. Few studies have assessed the temporal dynamics of PSFs among invasive plants, newly introduced plants and native plants. Here, we conducted a two‐stage PSF experiment to evaluate the temporal dynamics of PSFs among the invasive alien Phytolacca americana, the non‐invasive alien Phytolacca icosandra, and native Phytolacca acinosa. We conducted the experiment with different conditioning time periods. First, we planted the three species individually in pots to condition the soils. Then, each species was grown in a pot conditioned by the same species (‘home soil') or pots conditioned by one of the other two species (‘away soil'). Invasive and native plants produced higher biomass in home soils while non‐invasive alien plants produced higher biomass in away soils. The direction and intensity of PSFs varied with conditioning time among the three species and conditioning time had a significant effect on plant total biomass. Furthermore, sterilizing soils or adding activated carbon altered plant–soil feedbacks, indicating a role for microbes and allelopathic substances in mediating temporal changes. Our study indicates that changes in microbes and allelopathic substances in soils drove temporal changes in PSFs. Invasive alien plants can amplify their competitive advantage through PSFs and also potentially favor establishment of new non‐invasive alien plants.