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Purpose <p>Restoring ecosystem functions in sandy saline-alkali soils is intrinsically linked to microbial dynamics. This study investigated how organic and biological amendments (manure, biochar, and a microbial inoculant) influence soil properties, enzyme activities, and microbial communities across a 0–60&#xa0;cm profile to identify depth-dependent restoration mechanisms.</p> Methods <p>A field experiment was conducted using sheep manure, biochar, and a Bacillus-based inoculant. We integrated physicochemical analyses, extracellular enzyme assays, and high-throughput sequencing to evaluate microbial assembly and co-occurrence networks across stratified soil layers.</p> Results <p>The 20–60&#xa0;cm subsoil emerged as a critical microbial restructuring hotspot. Amendments significantly reduced electrical conductivity by up to 51.1% and altered nutrient availability in a depth-dependent manner, particularly by enriching available phosphorus (AP). db-RDA and marginal PERMANOVA identified AP as a shared explanatory factor for both bacterial and fungal community variation in the 20–60&#xa0;cm layer, while tNST analysis revealed a substantial increase in the deterministic component of microbial community assembly in the subsoil. Bacterial communities were more closely associated with salinity and moisture conditions, suggesting stress-alleviation responses, whereas fungal communities were more closely linked to AP and NH<sub>4</sub><sup>+</sup> availability, indicating resource-related responses. Network analysis revealed that manure promoted metabolic integration (enhanced connectivity), while biochar reinforced modular stability (modularity 0.729) without replacing dominant taxa like Pseudomonadota and Actinomycetota.</p> Conclusion <p>Organic and biological amendments alleviated salt-alkali stress and promoted pronounced microbial restructuring in the 20–60&#xa0;cm subsoil. These findings suggest that targeted subsoil microbial restoration, associated with downward resource transfer and depth-dependent assembly processes, is pivotal for optimizing long-term network stability and nutrient cycling in degraded saline-alkali ecosystems.</p>

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Subsoil microbial hotspots: divergent bacterial and fungal strategies in response to soil amendments in a saline-alkali profile

  • 期刊论文

  • 发表日期：

    2026年6月20日

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  • Haixia Huo,
  • Ying Zhao,
  • Mengchen Ju,
  • Jianguo Zhang

摘要

Purpose

Restoring ecosystem functions in sandy saline-alkali soils is intrinsically linked to microbial dynamics. This study investigated how organic and biological amendments (manure, biochar, and a microbial inoculant) influence soil properties, enzyme activities, and microbial communities across a 0–60 cm profile to identify depth-dependent restoration mechanisms.

Methods

A field experiment was conducted using sheep manure, biochar, and a Bacillus-based inoculant. We integrated physicochemical analyses, extracellular enzyme assays, and high-throughput sequencing to evaluate microbial assembly and co-occurrence networks across stratified soil layers.

Results

The 20–60 cm subsoil emerged as a critical microbial restructuring hotspot. Amendments significantly reduced electrical conductivity by up to 51.1% and altered nutrient availability in a depth-dependent manner, particularly by enriching available phosphorus (AP). db-RDA and marginal PERMANOVA identified AP as a shared explanatory factor for both bacterial and fungal community variation in the 20–60 cm layer, while tNST analysis revealed a substantial increase in the deterministic component of microbial community assembly in the subsoil. Bacterial communities were more closely associated with salinity and moisture conditions, suggesting stress-alleviation responses, whereas fungal communities were more closely linked to AP and NH4+ availability, indicating resource-related responses. Network analysis revealed that manure promoted metabolic integration (enhanced connectivity), while biochar reinforced modular stability (modularity 0.729) without replacing dominant taxa like Pseudomonadota and Actinomycetota.

Conclusion

Organic and biological amendments alleviated salt-alkali stress and promoted pronounced microbial restructuring in the 20–60 cm subsoil. These findings suggest that targeted subsoil microbial restoration, associated with downward resource transfer and depth-dependent assembly processes, is pivotal for optimizing long-term network stability and nutrient cycling in degraded saline-alkali ecosystems.