Deciphering the drivers of plant-soil feedbacks and their context-dependence: A meta-analysis

Plant-soil feedbacks (PSFs) play an important role in mediating plant species coexistence, community dynamics and ecosystem functioning. Soil biota (e.g. mutualists, pathogens), nutrient availability and secondary chemicals can drive the strength and direction of PSFs, but the variations and context-dependence of their effects remain unclear.

We used a phylogenetically controlled meta-analysis of 57 PSF studies across 166 plant species to explore whether and how these drivers affect individual PSFs (the performance of a species on conspecific versus heterospecific soils) and pairwise PSFs (indicating whether feedbacks promote stable or unstable species coexistence) under various intrinsic, environmental and experimental contexts.

Mutualists led to stronger positive individual and pairwise PSFs across various intrinsic and external contexts. However, PSFs became more negative when whole biota was present, with stronger negative effects on native species compared to exotic species and the most negative effects on plants experiencing interspecific competition. Manipulations of pathogens, nutrient availability and secondary chemicals had overall minimal influence on both types of PSFs, but the effect of nutrient availability on pairwise PSFs increased with increasing phylogenetic distance between species.

Our study suggests that soil biota is an important driver of PSFs and that plant origin and competitive context should be considered when predicting the role of soil biota in driving PSFs. Finally, we propose several directions for the next generation of PSF experiments towards a better understanding of the relative importance and interactions of different PSF drivers.