Root traits including root exudates are key factors affecting plant interactions with soil and thus play an important role in determining ecosystem processes. The drivers of their variation, however, remain poorly understood. We determined the relative importance of phylogeny and species ecology in determining root traits and analyzed the extent to which root exudate composition can be predicted by other root traits.We measured different root morphological and biochemical traits (including exudate profiles) of 65 plant species grown in a controlled system. We tested phylogenetic conservatism in traits and disentangled the individual and overlapping effects of phylogeny and species ecology on traits. We also predicted root exudate composition using other root traits.Phylogenetic signal differed greatly among root traits, with the strongest signal in phenol content in plant tissues. Interspecific variation in root traits was partly explained by species ecology, but phylogeny was more important in most cases. Species exudate composition could be partly predicted by specific root length, root dry matter content, root biomass, and root diameter, but a large part of variation remained unexplained.In conclusion, root exudation cannot be easily predicted based on other root traits and more comparative data on root exudation are needed to understand their diversity.

The aim of this study was to compare plant–soil interactions in the native range of two congeneric European species differing in their invasive success in the world: a globally invasive Cirsium vulgare and non-invasive C. oleraceum. We assessed changes in soil nutrients and soil biota following soil conditioning by each species and compared performance of plants grown in self-conditioned and unconditioned 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 establishment which benefited from the presence of unconditioned biota transferred by soil filtrate. Biomass of both species increased in soil with self-conditioned soil filtrate and decreased in soil with self-conditioned whole-soil inoculum compared to unconditioned filtrate and inoculum. However, the increase was smaller and the decrease greater for the invasive species. The invasive species allocated less biomass to roots when associated with harmful biota, reducing negative effects of the biota on its performance. The results show that in the native range the invasive species is more limited by self-conditioned pathogens and benefits more from unconditioned mutualists and thus may benefit more from loss of effectively specialized soil biota in a secondary range. Our study highlights the utility of detailed plant-soil feedback research in species native range for understanding factors regulating species performance in their native range and pinpointing the types of biota involved in their regulation.

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.

Increasing evidence suggests that plant invasions are promoted by altered plant-soil interactions. However, we still lack studies exploring differences in the effects of invasive and native species on soil properties, and particularly studies that would control for species phylogeny and abundance. Here, we grew seven congeneric pairs of invasive and native species with comparable cover in the studied region in a 12-weeks garden experiment. We analysed the amount of nutrients, pH and composition and amount of soil biota in soils cultivated by each species and in uncultivated soil. Then we used ratios of the soil characteristics in cultivated and uncultivated soil to express species effects on the soil. Invasive species used more phosphorus from the soil and supported mycorrhizal communities with higher potential to colonize plant roots than native species, but did not differ in any other soil properties. In contrast, we found strong differences among plant genera and genera from the same families tended to cluster together in their effects on the soil. We also found many interactions of genera and invasion status. Effects of plants on the soil were also largely determined by plant biomass production independent of species identity. The results suggest that invasive and native species differ only in a few general effects on the soil and that the differences among native and invasive species are largely genus specific. They also indicated that species phylogenetic identity and individual plant biomass should be considered in future studies of the effect of plants on the soil.