Biogeographical patterns of rhizosphere microbial communities in Robinia pseudoacacia forests along a north-south transect in the Loess Plateau

Rhizosphere microbiota play an essential role in plant productivity; however, their biogeographical patterns in restored forest ecosystems across large spatial scales remain poorly understood. We used the Ion S5TM XL sequencing platform to explore the distributions of microbial communities in the rhizosphere , bulk soil of Robinia pseudoacacia at 11 mature forest sites along a north-south precipitation gradient in the Loess Plateau, China. Microbial alpha-diversity mostly peaked in the south zone at lower latitudes , significant distance -decay patterns were observed in both bacterial and fungal communities. Fungal communities exhibited more distinct spatial patterns in the rhizosphere than bacterial communities. The relative influence of geographic factors on bacterial/fungal community turnover in the rhizosphere (12.4/16.7%) and bulk soil (16.1/17.1%) was greater than that of local environmental factors. Microbial community assembly was mainly governed by deterministic processes (98% of nearest taxon index > 2), despite their relative importance decreasing from bulk soil to the rhizosphere in the case of bacteria. Co-occurrence patterns of sensitive taxa were more complex in the bacterial network than in the fungal network owing to a marked regional effect. Interactions of bacterial taxa differentially enriched between soil compartments were much closer than fungal interactions, indicating a stronger rhizosphere effect on bacteria. The results provide novel insights into the assembly of rhizosphere microbial communities in large-scale forest ecosystems under vegetation restoration.

Automated summary

Rhizosphere microbiota play a crucial role in plant productivity, but their patterns in large-scale restored forest ecosystems are still poorly understood. This study used high-throughput sequencing to investigate microbial communities in rhizosphere and bulk soil of Robinia pseudoacacia trees along a precipitation gradient in the Loess Plateau, China. The results revealed distinct spatial patterns of microbial communities and highlighted the strong influence of geographic factors in shaping these communities. Importantly, the study provides valuable insights into the assembly of rhizosphere microbial communities in large-scale forest ecosystems under vegetation restoration.