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Plants often show remarkable elevational distribution patterns in arid‐montane ecosystems. However, it is not clear if soil microbes follow elevational diversity patterns, even though they represent the majority of biodiversity and drive varieties of ecological processes. Here, we conducted a survey of fungal and bacterial communities across an elevational gradient from 2350 to 3850 m in a typical mountainous grassland of arid northwestern China. Our results revealed co‐ordinated alpha and beta diversity patterns for soil microbes and plants along the elevational gradient, and the richness and Shannon diversity of bacteria, fungi, and plants exhibited a unimodal elevational pattern. The unimodal diversity pattern for soil microbes was further confirmed by the shifts in the relative abundance of dominant bacterial phyla (Actinobacteria, Firmicutes and Nitrospirae) and fungal phyla (Zygomycota) along the elevational gradient. Soil variables (soil pH, organic carbon, total nitrogen, available phosphorus, and nitrate nitrogen) explained the largest proportion of the variability in both bacterial and fungal communities, followed by plant (richness and Shannon diversity) and climatic (mean annual temperature and precipitation) variables. These environmental factors together explained a larger proportion of variability in bacterial communities (54.88%) than in fungal communities (24.15%). Our results strongly supported the existence of co‐ordinated elevational diversity patterns for soil microbes and plants in arid‐montane ecosystems, and highlighted that the importance of soil pH in microbial elevational patterns was also apparently in alkaline soils. Highlights: Soil bacteria and fungi follow elevational diversity patterns of plants.Species richness and Shannon diversity index exhibited unimodal elevational patterns.Soil, plant, and climatic factors are co‐responsible for microbial diversity.These factors explained more variation in bacteria than that in fungi.Microbial diversity is more vulnerable to precipitation than temperature. [ABSTRACT FROM AUTHOR]

Soil microorganisms are critical to soil health and environmental functions; however, the dynamics of microbial communities and their response to soil variables following conversion of desert soils to oasis farmland have not been well documented. We used high‐throughput pyrosequencing to investigate the dynamics of soil microbial communities along an irrigated cultivation chronosequence (cultivated for 16, 33, 45 and 60 years) and in adjacent non‐cultivated soil in a desert‐oasis ecotone in northwestern China. Additionally, we explored which soil variables may be responsible for shifts in microbial communities. Generally, cultivation in desert soil increased microbial community abundance and diversity; however, bacterial abundance and diversity increased along the cultivation chronosequence, whereas fungal abundance and diversity initially increased and then decreased. Continuous crop cultivation also resulted in a shift in microbial community composition, notably with a decrease in nitrogen (N)‐fixing microbes (Proteobacteria and Cyanobacteria) and an increase in ammonia‐oxidizing (Nitrosomonadales) and nitrite‐oxidizing microbes (Nitrospirae). Redundancy analysis showed that soil organic carbon, total N, available N, available phosphorus and bulk density explained over 80% of the variation in both bacterial and fungal communities; this indicated the critical roles of nutrient supply and soil structure in shaping the composition and diversity of microbial communities during the conversion of native desert soils to irrigated croplands. Highlights: Cultivation in desert soil increased microbial community abundance and diversity.Cultivation decreased N‐fixing microbes.Cultivation increased ammonia‐oxidizing and nitrite‐oxidizing microbes.Soil structure and nutrient supply shaped the diversity of microbial communities. [ABSTRACT FROM AUTHOR]