Unveiling soil microbial dynamics: insights into bacterial community responses to solonetz dealkalinization

Soil microbiome plays a crucial role in maintaining soil fertility and nutrient cycling, offering potential solutions for soil restoration. However, there remains a notable gap in the understanding of how bacterial communities respond to soil dealkalinization. The research aims to investigate the microbial dynamics of soil bacterial communities during soil dealkalinization.

Soil dealkalinization in situ is a long recovery process that directly modifies soil properties. Here, we applied a “reverse dealkalinization” approach to gradually introduce sodium carbonate into a previously dealkalized cropland soil, thereby constructing distinct stages of soil dealkalinization. Soil physicochemical properties as well as the abundance, diversity and community assembly of soil bacteria were analyzed.

In situ and mesocosmic dealkalinizationconsistently altered soil alkalinity. The exchangeable sodium percentage (ESP) decreased from 32.5% in alkalic soil to 0.5% in the dealkalized soil. Soil dealkalinization significantly increased soil respiration activity and bacterial diversity but reduced the complexity of bacterial networks. The β-nearest taxon index indicated that deterministic processes predominantly governed microbial community assembly during soil dealkalinization. A small portion of soil microbiome (ranging from 3.0 to 8.6%) responded positively to soil dealkalinization including well-recognized phylotypes such as Alysiosphaera, Nocardiodes, and Vicinamibacterales and uncultivable lineages such as Gemmatimonadaceae. Random forest analyses highlighted soil alkalinity and nitrate levels as key factors influencing microbial community dynamics during soil dealkalinization.

Our findings suggested that only a small portion of soil microbiota could serve as an early and sensitive indicator of soil dealkalinization. Thus, targeting these key phylotypes may be crucial for soil fertility improvement during soil dealkalinization.