Mechanistic insights into rhizosphere microbiome assembly in Pinus tabuliformis: The role of cross–kingdom interactions and soil salinity gradients

Abstract

Soil salinization caused by desertification and drought severely limits agricultural and forestry development. The rhizosphere core microbiome plays a vital role in helping host plants cope with environmental stress. However, in saline-alkali soils, it remains unclear how bacterial and fungal communities in the rhizosphere of Pinus tabuliformis interact and collectively respond to environmental factors to influence the plant. This study aims to identify the composition and functional potential of the core bacterial and fungal microbiota in the rhizosphere of P. tabuliformis in saline environments, as well as their interactions with environmental factors, thus providing a theoretical basis for utilizing core rhizosphere microbial resources. We performed high-throughput sequencing of root samples from P. tabuliformis at four locations. We analyzed the community structure and functional profiles of bacteria and fungi and their relationships with soil physicochemical properties. The environmental factors most influencing the number of core bacterial species were organic matter (OM), Na⁺, and total potassium (TK). Meanwhile, total phosphorus (TP) was the most influential soil factor for core fungal species. Correlation analysis showed that TN, TP, and pH significantly affected both bacterial and fungal community variation (P < 0.05). Co-occurrence network analysis indicated complex cross–kingdom interactions between core bacterial and fungal taxa. Functional predictions suggested that bacterial communities exhibit both potential pathogenicity and stress resistance, while fungal communities are more saprotrophic and sensitive to environmental changes. Microbial communities at the SYH site displayed a "high pathogenicity–low resistance" profile, contrasting with those at the MC site. Correlation network analysis further uncovered complex mutualistic and competitive relationships among core bacterial and fungal genera. This study demonstrates that P. tabuliformis rhizosphere bacterial and fungal communities respond collaboratively to salinity stress through functional complementarity, such as bacterial enrichment in stress resistance and fungal dominance in saprotrophy. These findings may offer new insights into enhancing the adaptability of P. tabuliformis and improving sandy land ecosystems by targeted management of the soil microbiome.