Abstract:

Aims: Plant-soil feedback (PSF) is an ecological process in which plants transform the rhizosphere soil environment through growth, thereby impacting the subsequent growth and development of plants. Invasive plants may undergo adaptive evolution, therefore causing different effects on soil environments and impacting the strengths of PSF. Previous studies on PSF of invasive plants focused on comparing the differences between invasive and native plants or between invasive and other invasive species. However, there are relatively few studies dealing with the differences between introduced and native populations (invasive and non-invasive populations) of invasive plants. To address this gap, we conducted an experiment with Alternanthera philoxeroides to study whether native and introduced populations of invasive plants differ in plant-soil feedback in introduced area and how soil microorganisms affect the feedback results. Specially, we addressed the following questions: (1) Is there a difference in PSF between native and introduced populations in the area introduced by A. philoxeroides? (2) Is there a difference in the diversity of the soil rhizosphere microbial community between native and introduced populations of A. philoxeroides?

Methods: We conducted a common garden experiment in Jiangwan Campus of Fudan University (121°30° E, 31°20° N), Shanghai City in which we grew sixteen populations of the invasive plant A. philoxeroides collected from both the native (Argentina) and the introduced range (China). After nine weeks of growing, we harvested the plants and processed the soil to measure: bacterial diversity (i.e., bacterial richness and bacterial Shannon index), and fungal diversity (i.e., fungal richness and fungal Shannon index). We then cultivated three types of soil (soil conditioned by native populations, soil conditioned by introduced populations and controlled soil) to test their PSF. After five weeks of growing, all plants were collected and the following variables were measured: (1) total biomass, (2) aboveground biomass, (3) underground biomass, and (4) storage root biomass.

Results: The PSF from introduced A. philoxeroides populations was positive while the PSF of native populations was neutral. The introduced populations showed significant increases in soil bacterial richness (+ 118.3%), bacterial Shannon index (+ 70.0%), fungal richness (+ 76.3%) and fungal Shannon index (+ 193.2%). However, there was no significant difference between the soils conditioned by native populations and the controlled soil.

Conclusions: These results indicate that in the process of dispersal, the regulation of soil microorganisms by the introduced populations of A. philoxeroides has changed, producing positive plant-soil feedback. Our results provide new experimental evidence for the transformation of PSF in invasive species. Furthermore, we provide a theoretical basis for exploring the mechanisms of successful invasion by alien plants in the future which is necessary for the control and prevention of future plant invasion.

Key words: plant-soil feedback, plant invasion, evolution, microorganism