The temporal development of plant-soil feedback is contingent on competition and nutrient availability contexts

Distinct effects of phyllosphere and rhizosphere microbes on invader Ageratina adenophora during its early life stages

Microbes strongly affect invasive plant growth. However, how phyllosphere and rhizosphere soil microbes distinctively affect seedling mortality and growth of invaders across ontogeny under varying soil nutrient levels remains unclear. In this study, we used the invader Ageratina adenophora to evaluate these effects. We found that higher proportions of potential pathogens were detected in core microbial taxa in leaf litter than rhizosphere soil and thus leaf inoculation had more adverse effects on seed germination and seedling survival than soil inoculation. Microbial inoculation at different growth stages altered the microbial community and functions of seedlings, and earlier inoculation had a more adverse effect on seedling survival and growth. The soil nutrient level did not affect microbe-mediated seedling growth and the relative abundance of the microbial community and functions involved in seedling growth. The effects of some microbial genera on seedling survival are distinct from those on growth. Moreover, the A. adenophora seedling-killing effects of fungal strains isolated from dead seedlings by non-sterile leaf inoculation exhibited significant phylogenetic signals, by which strains of Allophoma and Alternaria generally caused high seedling mortality. Our study stresses the essential role of A. adenophora litter microbes in population establishment by regulating seedling density and growth.

Global patterns and drivers of plant-soil microbe interactions

Plant-soil feedback (PSF) is an important mechanism determining plant community dynamics and structure. Understanding the geographic patterns and drivers of PSF is essential for understanding the mechanisms underlying geographic plant diversity patterns. We compiled a large dataset containing 5969 observations of PSF from 202 studies to demonstrate the global patterns and drivers of PSF for woody and non-woody species. Overall, PSF was negative on average and was influenced by plant attributes and environmental settings. Woody species PSFs did not vary with latitude, but non-woody PSFs were more negative at higher latitudes. PSF was consistently more positive with increasing aridity for both woody and non-woody species, likely due to increased mutualistic microbes relative to soil-borne pathogens. These findings were consistent between field and greenhouse experiments, suggesting that PSF variation can be driven by soil legacies from climates. Our findings call for caution to use PSF as an explanation of the latitudinal diversity gradient and highlight that aridity can influence plant community dynamics and structure across broad scales through mediating plant-soil microbe interactions.