Enhanced productivity of maize through intercropping is associated with community composition, core species, and network complexity of abundant microbiota in rhizosphere soil

High crop diversity can potentially enhance farmland productivity and ecosystem services, through direct or indirect effects, particularly belowground. Intercropping is a powerful technique to increase crop diversity and belowground biodiversity. It has attracted long-term global attention. However, little is known about the impacts of belowground microbiota on intercropping-driven increases in crop productivity. This study was an 8-year experiment involving five maize planting patterns, which aimed to distinguish the contributions of rare and abundant microbiota (bacteria, fungi, and eukaryotes) in rhizosphere soil to support maize production. The results indicated that the richness and phylogenetic diversity of rare microbial taxa were significantly higher than those of abundant taxa across all soil samples. Maize and soybean intercropping increased the diversity of rare taxa rather than abundant taxa. Plant growth stages significantly altered the community composition of both rare and abundant microbial taxa. The assembly of the rare and abundant communities is mainly driven by deterministic processes and, in particular, the abundant taxa rather than the rare taxa mainly contributed to maize productivity gain. The changes in maize productivity were significantly associated with many core species in the abundant microbial communities mainly belonging to bacterial Actinomycetales and Rhodocyclaceae, fungal Tausonia and Curvularia, and eukaryotic Leptophyryidae and Ochromonadaceae. The network complexity of abundant fungi and eukaryotic communities also exerted notable effects on maize productivity. Overall, these findings underscored the importance of the core taxa and network stability of abundant microbiota in intercropping systems. This suggests the potential of intercropping to improve crop production by regulating belowground microbial effects in intensive agroecosystems.