Abstract: Soil microorganisms, which include many rare taxa and a small number of abundant taxa, have different contributions to the ecosystem functions and services. High throughput sequencing technology was used to analyze the species composition of soil samples by DNA sequencing. Soil microorganisms were divided into abundant taxa and rare taxa to reveal their composition. Correlation analysis and random forest method were used to further analyze the influence of environmental factors on the community. Finally, the beta nearest taxon index (βNTI) based on the null model was used to elucidate the mechanisms underlying soil microbial community assembly. We found that, in desert soil, the community assembly of rare bacteria was almost entirely dominated by a homogeneous selection of deterministic processes. For comparison, stochastic processes had more pronounced effects on the abundant bacteria. However, both abundant and rare fungi exhibited similar patterns of community assembly, i.e. deterministic and stochastic processes jointly determined the assembly processes of fungal communities. We also observed that community assembly shifted from stochastic to deterministic processes with increasing mean annual precipitation (MAP) and mean annual temperature (MAT) for abundant bacteria. Conversely, for rare fungi, there was an inclination toward a shift from deterministic to stochastic processes with rising MAT. In conclusion, our findings provide compelling evidence that MAT and MAP regulate the community assembly process of abundant and rare microbial communities in desert soil. These findings establish a theoretical foundation for future investigations into the community structure and ecological functions of soil microorganisms.

Key words: biogeography, deterministic processes, stochastic processes, abundant taxa and rare taxa, climatic factors