Halophyte-Specific Rhizosphere Effects Drive the Differentiation of Microbial Community Assembly in a Desert-Grassland Salt Marsh

Arid salt marsh ecosystems endure chronic water scarcity and high salinity stress, with the stability of their functions inextricably linked to the pivotal role of the rhizosphere microenvironment of halophytes. This study focused on three typical halophytes (<i>Kalidium cuspidatum, Nitraria tangutorum, Reaumuria soongarica</i>) in the Jiantan wetland, and deeply explore how these halophytes differently regulate the soil microenvironment through the rhizosphere effect. The results showed that the rhizosphere soil of <i>Kalidium cuspidatum</i> had higher pH, Na⁺, and K⁺ contents, while the rhizosphere soil of <i>R. soongarica</i> had higher total carbon, soil organic carbon, alkali-hydrolyzable nitrogen, and microbial biomass. Microbial community analysis revealed that rhizosphere soil of fungal diversity was significantly higher in <i>K. cuspidatum</i> than in <i>R. soongarica</i>, with distinct differences in bacterial and fungal community structures. These differences were closely associated with factors such as Na⁺, Olsen phosphorus, microbial biomass carbon and alkali-hydrolyzable nitrogen. Among the dominant phyla, Proteobacteria and Ascomycota predominate, with <i>Desulfobacterota</i> and <i>Mortierellomycota</i> exhibiting the highest explanatory power (>48%) for physicochemical property variations. The microbial network of rhizosphere soil of <i>R. soongarica</i> has the highest complexity (with 633 nodes and 3300 edges), but the proportion of positive correlation edges was the lowest (21.58%). Structural equation modeling indicates that soil physical properties indirectly influence network complexity by negatively regulating chemical properties and microbial biomass, while microbial diversity had a direct positive effect on dominant phylum composition and network complexity. This study elucidated the differentiated adaptive strategies of rhizosphere microenvironment-microbe interactions in halophytes, providing a theoretical basis for wetland ecological restoration.