Available Nitrogen as the Determinant of Variability in Soil Microbial Communities Throughout Lycium chinense Growth Zones in the Qaidam Basin, Qinghai, China

Understanding the compositional and functional dynamics of soil microbial communities is crucial for optimizing soil fertility and promoting agricultural sustainability. In this study, the spatial variability of soil properties and microbial communities was investigated across four Lycium chinense growing regions (Golmud, Dengle, Delingha and Ulan) around Qaidam Basin in China, aiming to explore their relationships and implications for soil management. Soil samples were collected from four Lycium chinense growing regions around the Qaidam Basin, China, and analyzed for changes in bacterial and fungal communities using high-throughput amplicon sequencing targeting the 16S rRNA gene and ITS region, respectively. The results showed spatial heterogeneity of soil fertility around the Qinghai Basin. The soil organic matter peaked at 17.89 g/kg in WL, compared to a low of 6.72 g/kg in GLMD, while soil nitrate concentrations reached a maximum of 188.91 mg/kg in WL versus 47.48 mg/kg in GLMD. The soil nitrate and ammonium concentrations emerged as a key factor influencing the β -diversity of microbial communities, despite having no significant effect on α -diversity. Through network analysis and Z-P plots, 53 keystone microbial taxa such as Truepera , Metarhizium , and Gemmatimonas were identified, which were closely associated with nitrogen fixation, nitrification, and denitrification, suggesting essential roles in nitrogen cycling and ecosystem stability. Furthermore, the nutrient-rich eastern regions had more complex microbial co-occurrence networks and a greater abundance of keystone microbial species compared to the nutrient-poor western regions. In conclusion, this study offers insights into soil management to enhance soil health and promote sustainable agricultural production in high-altitude areas.