Similarity in fine-to-total root mass ratio leads to comparative plant-soil feedbacks between co-occurring native and invasive plants.
Aims: Soil biota can affect plant-plant interactions and non-native plant invasions via plant-soil feedback (PSF). Understanding the drivers underlying interspecific variations in PSF is important for predicting the role of soil biota in non-native plant invasions. Recent studies found that PSF could be predicted by plant traits. The success of plant invasions is also linked with plant traits, suggesting a potential linkage between PSF and plant invasion via plant traits, but has not yet been tested. Here, we compared PSF between six phylogenetically paired co-occurring native and invasive plants, and explored the potential linkage between PSF with plant root traits. Methods: We conducted a two-phase PSF experiment. Field collected soils were conditioned by the six plant species for 3 months firstly, then seedlings of these plants were grown in living or sterilized soils that had been conditioned by conspecific vs. heterospecific (the congener/confamilial species) individuals. We estimated effects of biota in conspecific (conspecific PSF) or heterospecific (heterospecific PSF) soils relative to sterilized soils, and the relative effects of biota in conspecific vs. heterospecific soils (PSF-away) on plant biomass. Important Findings: In general, soil biota suppressed plant growth, and there were no differences in conspecific PSF, heterospecific PSF and PSF-away between native and invasive plants. PSF increased with rising plant fine-to-total root mass ratio in the presence of soil biota, and its value was comparable between native and invasive plants. Our results indicate that similarity in plant fine-to-total root mass ratio that predicted PSF may have partially led to the comparable PSFs between these native and invasive plants. Studies exploring the linkages among plant traits, PSF and plant invasions with more plants, in particular phylogenetically distant plants, are needed to improve our understanding of the role of soil biota in plant invasions.