Abstract: Aims Long-term grazing profoundly affects the external environment for plant growth and development in grassland ecosystems, and plants adapt to environmental changes through interactions with rhizosphere microbes. However, there is limited research on how grazing affects the rhizosphere microbial diversity of plants with different survival strategies in grasslands. Methods In this study, based on the long-term grazing experimental platform of typical grasslands in Inner Mongolia, we selected the dominant plant species Stipa grandis and Cleistogenes squarrosa as research subjects. Using high-throughput sequencing technology, we explored the trends in rhizosphere bacterial diversity under different grazing intensities (control, light: 1.5 sheep·hm–2, moderate: 4.5 sheep·hm–2, and heavy: 7.5 sheep·hm–2), and analyzed the differences in the responses of two dominant plant rhizospheric bacteria and their intrinsic connection with plant functional traits. Important findings The results showed that: (1) Heavy grazing significantly reduced the rhizosphere bacterial richness (8.97%) and Chao1 index (9.48%) in Stipa grandis, but had no significant effect on the rhizosphere bacterial α-diversity of Cleistogenes squarrosa. Additionally, the α-diversity of Stipa grandis was significantly lower than that of Cleistogenes squarrosa. Moreover, heavy grazing significantly altered the bacterial community composition of both plant species, with the change being more pronounced in Stipa grandis than in Cleistogenes squarrosa. (2) As grazing intensity increased, Stipa grandis was enriched with both plant growth promoting rhizobacteria and biocontrol agents, Cleistogenes squarrosa whereas was primarily enriched with plant growth promoting rhizobacteria. (3) Changes in the diversity and relative abundance of rhizosphere bacterial communities in Stipa grandis were significantly correlated with its larger root diameter, lower specific leaf area, and lower specific root length, which reflect grazing avoidance and resource-conserving strategies. In contrast, changes in the bacterial communities of Cleistogenes squarrosa were significantly correlated with its higher C/N ratio in aboveground biomass and larger specific leaf area, which reflect grazing tolerance and resource-consuming strategies. In conclusion, this study demonstrated that the responses of rhizosphere bacterial communities in different dominant plant species to grazing pressure are closely related to their survival strategies, enriching our understanding of the synergistic adaptations between plants and rhizosphere microbial communities in the context of long-term grazing.

Key words: Grazing Intensity, Dominant Plants, Rhizosphere Bacteria, Plant Functional Traits, Microbial Functional Groups