Positive plant–soil feedbacks of the invasive Impatiens glandulifera and their effects on above-ground microbial communities

Abstract

Impatiens glanduliferais one of the most widespread invasive plant species in the UK. Although aspects of its biology are known, there is little information about its association with microbial communities, both above ground and below ground. Furthermore, it is unknown whether this species exhibits any form of plant–soil feedback (PSF), commonly seen in other invasive weeds. We conducted a PSF experiment, in which plants ofI.glanduliferawere grown in soil that supported the species and compared with plants grown in a control soil from the same locality. Soil nutrients were measured, and the soil and foliar microbial communities were assessed.Impatiens glanduliferagrew larger and faster in conditioned soil compared with the control. Higher levels of phosphate were also found in conditioned soils. Arbuscular mycorrhizal fungal (AMF) colonisation was lower in conditioned soils, suggesting thatI.glanduliferamay rapidly alter AMF communities in invaded areas. PSFs had a significant effect on the foliar endophyte community, with clear separation of species between conditioned and control soils. These results show thatI.glanduliferadisplayed a positive PSF and the PSF mechanism extended beyond the soil microbial community to affect foliar endophytes. The observed increase in endophytes in plants grown in conditioned soil could enhance resistance to herbivory, thus further accentuating the invasive properties of this species.