Tree species identity is associated with rhizosphere microbiome assembly via root metabolite‐mediated feedbacks in subtropical forests

The rhizosphere microbiome is critical for forest ecological functions, yet the mechanisms through which tree species identity and neighbour tree interactions are associated with its assembly remain poorly understood. Using Illumina MiSeq and liquid chromatography–mass spectrometry (LC–MS), we investigated how tree species (pine vs. liquidambar) and forest composition (pure vs. mixed) shape rhizosphere microbial communities and root metabolites in subtropical forests. Rhizosphere fungal community structure differed significantly across rhizosphere types, whereas bacterial community and metabolite profiles differed primarily between the pure pine forest and other forest types. Predicted functional shifts included a decline in cellulolytic bacteria (−27%) and an increase in denitrifying groups (+54%), with ectomycorrhizal fungi enriched in mixed than pure forests ( p < 0.05). Metabolite profiling revealed that lipids, organic acids and sugars were the most abundant compound classes, with 55 metabolites differentially abundant between pure pine and mixed forest rhizospheres. Rhizosphere metabolite profiles were significantly correlated with microbial community structure ( p < 0.05). Specific microbe–metabolite associations were identified; fatty acids positively correlated with oligotrophic bacteria (WPS‐2), sugars with denitrifiers ( Reyranella ) and dipeptides with the beneficial fungus Penicillium . These results demonstrate that tree species identity is associated with rhizosphere microbiome assembly via root metabolite‐associated feedbacks, which correlate with soil nutrient cycling. This provides a mechanistic, function‐oriented framework for understanding plant–microbiome interaction and harnessing them to enhance ecosystem resilience. Read the free Plain Language Summary for this article on the Journal blog.