Microbial diversity response to abiotic and biotic factors provides a sensitive indicator for estimating the potential stability and degradation of soils in agro‐ecosystems. To determine the effects of pH on organic phosphorus mineralization and microbial diversity, phospholipid fatty acid analysis, quantitative polymerase chain reaction (qPCR), and multiple ecological analyses were performed. Significant correlations were found between phosphorus components and alkaline phosphatase, phytase, and pH, between phoD and phytase, between bpp and alkaline phosphatase. phoD and bpp gene abundance presented significant linear relationships with soil pH and microbial diversity. Abiotic and biotic factors explained 25.1% of the total variation in organic phosphorus‐mineralizing‐related gene abundance, and abiotic factors accounted for 13.2% of the total variation in microbial community composition. Soil pH was the determinant, accounting for 11.2 and 7.7% of the total variation in organic phosphorus‐mineralizing‐related gene abundance and microbial community composition, respectively. Our results emphasized that the phosphorus components, pH, and organic phosphorus‐mineralizing‐related gene abundance were responsible for organic phosphorus‐mineralizing‐related enzyme activity. To our knowledge, this is the first report that pH is a key factor in directly and indirectly determining organic phosphorus‐mineralizing‐related gene abundance, which in turn affects microbial diversity, on a large spatial scale. The differences in phosphorus components, enzyme activity, organic phosphorus‐mineralizing‐related gene abundance, microbial community composition and diversity caused by pH might explain crop yield reduction.

Bacterial diversity and ecosystem multifunctionality (EMF) vary along environmental gradients. However, little is known about interconnections between EMF and taxonomic and phylogenetic diversities of rare and abundant bacteria. Using MiSeq sequencing and multiple statistical analyses, we evaluated the maintenance of taxonomic and phylogenetic diversities of rare and abundant bacteria and their contributions to EMF in salinized agricultural soils (0.09 to 19.91 dS/m). Rare bacteria exhibited closer phylogenetic clustering and broader environmental breadths than abundant ones, while abundant bacteria showed higher functional redundancies and stronger phylogenetic signals of ecological preferences than rare ones. Variable selection (86.7%) dominated rare bacterial community assembly, and dispersal limitation (54.7%) and variable selection (24.5%) determined abundant bacterial community assembly. Salinity played a decisive role in mediating the balance between stochastic and deterministic processes and showed significant effects on functions and diversities of both rare and abundant bacteria. Rare bacterial taxonomic α-diversity and abundant bacterial phylogenetic α-diversity contributed significantly to EMF, while abundant bacterial taxonomic α-diversity and rare bacterial phylogenetic α-diversity did not. Additionally, abundant rather than rare bacterial community function had a significant effect on soil EMF. These findings extend our knowledge of environmental adaptation of rare and abundant bacteria and highlight different contributions of taxonomic and phylogenetic α-diversities of rare and abundant bacteria to soil EMF. IMPORTANCE Soil salinization is a worldwide environmental problem and threatens plant productivity and microbial diversity. Understanding the generation and maintenance of microbial diversity is essential to estimate soil tillage potential via investigating ecosystem multifunctionality. Our sequence-based data showed differences in environmental adaptations of rare and abundant bacteria at taxonomic and phylogenetic levels, which led to different contributions of taxonomic and phylogenetic α-diversities of rare and abundant bacteria to soil EMF. Studying the diversity of rare and abundant bacteria and their contributions to EMF in salinized soils is critical for guiding soil restoration.

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