Distinct Bacterial Communities Within the Nonrhizosphere, Rhizosphere, and Endosphere of Ammodendron bifolium Under Winter Condition in the Takeermohuer Desert

Due to human activities and severe climatic conditions, the population of Ammodendron bifolium, an excellent sand-fixing plant, has gradually decreased in the Takeermohuer Desert. The plant-associated bacteria community can enhance its survival in harsh environments. However, the understanding of A. bifolium-associated bacterial community is still unclear during the harsh winter. We investigated the bacterial community structure from the A. bifolium rhizosphere and nonrhizosphere at different depths (i.e., 0-40 cm, 40-80 cm, 80-120 cm) and from endosphere (i.e., root endosphere and stem endosphere) in winter. At the same time, we analyzed the impact of different compartments and soil factors on the bacterial community structure. Studies have shown that the A. bifolium rhizosphere exhibits higher levels of SOM (soil organic matter), SOC (soil organic carbon), SAN (soil alkaline nitrogen), and SAK (soil available potassium) compared with the nonrhizosphere. The dominant bacterial phyla were Proteobacteria (19.6%), Cyanobacteria (15.9%), Actinobacteria (13.6%), Acidobacteria (9.0%), and Planctomycetota (5.7%) in the desert. Proteobacteria (24.0-30.2%) had the highest relative abundance in rhizosphere, Actinobacteria (18.3-22.6%) had the highest relative abundance in nonrhizosphere, and Cyanobacteria had the highest relative abundance in endosphere. At the genus level, the relative abundance of Pseudomonas (1.2%) in the root endosphere was the highest and the other genera were mostly unclassified. The Chao1 and PD_whole_tree indices showed that the diversity of the bacterial communities decreased from nonrhizosphere, rhizosphere, root endosphere to stem endosphere. Co-occurrence network analyses identified Proteobacteria and Actinobacteria as key species across the three compartments. Additionally, unique keystone species like Cyanobacteria, Verrucomicrobiota, and Desulfobacterota were found only in the endosphere. The bacterial community in the rhizosphere was influenced by factors such as EC (electrical conductivity), STC (soil total carbon), SOM, SOC, STN (soil total nitrogen), SAN, STP (soil total phosphorus), and SAK, while that of the nonrhizosphere was mainly influenced by pH, C/N (STC/STN), SAP, and distance. The study highlighted differences in bacterial community composition, diversity, and influencing factors across the three compartments, which can provide a better understanding of the association/interactions between A. bifolium and bacterial communities and lay a foundation for revealing its adaptability in winter.