Plant–soil feedback is dependent on tree mycorrhizal types and tree species richness in a subtropical forest

Abstract

Plant-soil feedback (PSF) is an important driver of plant species coexistence and diversity maintenance. However, it remains unclear how changes in PSF due to decline in tree species richness influence the performance of arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) tree species. A PSF experiment was established with eight target tree species (four AM and four EcM tree species) based on a subtropical forest Biodiversity-Ecosystem Functioning Experimental in China (BEF-China) platform, where soil inocula were collected beneath the canopy of target tree species individuals growing in monoculture and eight tree-species mixture plots. We hypothesized that the negative PSF strength of AM tree species would be stronger in monocultures than that in eight tree-species mixtures, resulting in better performance in highly diverse plant communities, whereas EcM tree species would benefit less from tree species richness. However, the results showed consistent PSFs of AM tree species regardless of tree species richness. In contrast, EcM tree species experienced a change from positive in monocultures to negative PSF in eight tree-species mixtures, influencing the performance of EcM tree seedlings. With high concern of the cascading effects of tree species richness on PSFs via modulating soil fungal communities, we revealed that the alterations in EcM fungal abundance, putatively pathogenic fungal diversity, and fungal co-occurrence network complexity mirrored those of PSF associated with EcM tree species, showing the changes from positive in monocultures to negative feedback in eight tree-species mixtures. Our findings highlight the differential PSFs exhibited by AM and EcM tree species in response to tree species richness, and provide insight into the potential role of fungal functional guilds and co-occurrence network complexity in shaping the PSFs of them.