Background and aims

Rhizosphere is the main interface for nutrients and energy exchange among plants, soil, and microorganisms. However, the influence of plant traits on rhizosphere microorganisms remains largely obscure, especially under long-term nutrient enrichment in temperate steppes. This study aims to investigate the importance of plant root and leaf traits, and rhizosphere soil properties in driving the response of rhizosphere bacterial and fungal communities to long-term nitrogen (N) and phosphorus (P) enrichment.

Methods

We evaluated the responses of plant traits, rhizosphere soil properties, and rhizosphere bacterial and fungal communities of dominant species to 15-year N and P addition in a temperate steppe.

Results

Long-term N addition decreased the rhizosphere bacterial diversity and altered the bacterial and fungal community compositions and structures. However, microbial communities were relatively insensitive to P addition. Furthermore, the underlying mechanisms of the shifts in fungal and bacterial community structures differed. The fungal community structures were primarily influenced by plant species identity, which was largely attributed to the root traits of host plants. Specifically, root diameter and specific root length, which exhibited considerable interspecific variation, were the most important factors regulating the fungal community structures. In contrast, bacterial community structures were strongly correlated with the N enrichment-induced changes in soil pH.

Conclusion

Our results revealed that root traits of host plants play crucial roles in regulating rhizosphere fungal communities under both ambient and long-term nutrient enrichment conditions in a temperate steppe, which provide new insights for our understanding of correlations between plant and rhizosphere microbiomes.