Plant-soil interactions of an invasive plant species and its non-invading congener differ in soil from their original range

Abstract

The aim of this study was to compare plant-soil feedback (PSF) of globally invasive Cirsium vulgare in its native range with its non-invading congener C. oleraceum. We assessed changes in soil nutrients and biota following soil conditioning by each species and compared performance of plants grown in self-conditioned and control soil, from which all, some or no biota was excluded. The invasive species depleted more nutrients than the non-invasive species and coped better with altered nutrient levels. The invasive species had higher seedling emergence which benefited from the presence of unconditioned (non-specific) microbes. Biomass of the invasive species increased less in presence of self-conditioned microbiota and decreased more in presence of self-conditioned larger-sized biota compared to unconditioned biota than biomass of the non-invasive species. The invasive species showed greater ability to decrease its root-shoot ratio in presence of harmful biota and thus reduce their negative effects on its performance.The results show that the invasive species is more limited by self-conditioned pathogens in the native range and benefits more from unconditioned mutualists, and thus may benefit more from loss of specialized soil biota in a secondary range. Our study highlights the utility of detailed PSF research in the native range of species for understanding the factors that regulate performance of invasive and non-invasive species in their native range, and for pinpointing the types of biota involved in their regulation and how this regulation changes across the plants life cycle.