Effects of salinity on photosynthetic characteristics, rhizosphere microbial community structure, and diversity of Ulmus pumila L.

Salt stress is a key abiotic limiting factor restricting agricultural productivity, making the screening and breeding of salt-tolerant plants essential for alleviating soil salinization. Ulmus pumila, a native Chinese tree with fast growth, good wood properties and high tolerance to salt stress and drought, was investigated to reveal its salt adaptation and underlying mechanisms. This study applied phenotypic identification, physiological determination and high-throughput sequencing to analyze growth traits and rhizosphere microbial communities under low, moderate and high salt stress. Our findings revealed that salt stress significantly inhibited seedling height, ground diameter, biomass and other growth indexes in a salinity-dependent manner. Distinct mineral element allocation existed between stems and leaves, with leaves as the main accumulation organ, and U. pumila adapted to salt stress by regulating element distribution and maintaining ion homeostasis. Bacterial communities were more sensitive to salt stress than fungi: Proteobacteria increased while Actinobacteria decreased with elevated salinity, and Ascomycota-dominated fungal communities remained structurally stable. Salt stress reshaped microbial co-occurrence networks, with bacteria adapting via species turnover and fungi maintaining function through core taxa. Ulmus pumila resists salt stress via integrated strategies of growth regulation, physiological adjustment and rhizosphere microbial synergy, providing a scientific basis for saline-soil vegetation restoration, afforestation and soil sustainable improvement.