<UnorderedList Mark="Bullet"> <ItemContent> Reduced microbial diversity and network complexity—High salinity treatments corresponded to lower microbial diversity and a simpler network structure, indicating reduced community complexity under elevated salt stress. </ItemContent> <ItemContent> Divergent bacterial–fungal strategies—Bacteria maintained a balance between deterministic selection and stochastic drift, with a shift toward mixed processes under extreme salinity, whereas fungal communities were consistently dominated by stochastic processes, primarily driven by dispersal limitation and ecological drift. </ItemContent> <ItemContent> Network shifts to keystone halotolerants—Halotolerant taxa become keystone nodes in simplified co-occurrence networks, sustaining partial ecosystem functions despite reduced connectivity. </ItemContent> </UnorderedList>Soil salinization, an accelerating form of land degradation, is reshaping terrestrial ecosystems worldwide. Although salinity is recognized as a strong environmental filter, its influence on bacterial and fungal communities remains insufficiently understood beyond taxonomic shifts. Here, we conducted a controlled irrigation experiment simulating salinity gradients to disentangle how diversity, network interactions, and assembly processes of bacteria and fungi respond to increasing salt stress. Results showed that high salinity significantly suppressed microbial richness, while mild salinity enhanced diversity, indicating a dual role of salinity as both stressor and structuring factor. Bacterial communities underwent pronounced taxonomic shifts, with halotolerant taxa dominating under high salinity, whereas fungal taxonomic composition remained relatively stable. Network analyses revealed that low salinity supported complex and resilient microbial networks, but high salinity simplified structures, reduced stability, and shifted keystone taxa toward tolerant groups. Fungal networks declined more sharply in connectivity than bacterial ones, reflecting higher vulnerability. Assembly process analyses demonstrated that bacteria, flexibly shifting under stress, while fungi were consistently governed by stochastic processes dominated by drift and dispersal limitation. These findings identify salinity thresholds as critical drivers of microbial ecological strategies and provide a mechanistic framework linking diversity loss, network fragility, and assembly shifts. Overall, our results reveals the differences of soil bacterial and fungal community construction under saline-alkali stress, providing an important theoretical basis for understanding the response of microorganisms to environmental changes and the ecological restoration of saline-alkali soils.

Salinity gradients drive bacterial–fungal divergence through diversity variation, network fragility, and stochastic assembly in saline-alkali soils

期刊论文
发表日期：

2026年7月24日

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Xiaoxuan Ma,
Lijuan Chen,
Changsheng Li,
Jinxia Zhang,
Kaiyuan Gan,
Qi Feng

摘要

Reduced microbial diversity and network complexity—High salinity treatments corresponded to lower microbial diversity and a simpler network structure, indicating reduced community complexity under elevated salt stress.

Divergent bacterial–fungal strategies—Bacteria maintained a balance between deterministic selection and stochastic drift, with a shift toward mixed processes under extreme salinity, whereas fungal communities were consistently dominated by stochastic processes, primarily driven by dispersal limitation and ecological drift.

Network shifts to keystone halotolerants—Halotolerant taxa become keystone nodes in simplified co-occurrence networks, sustaining partial ecosystem functions despite reduced connectivity.

Soil salinization, an accelerating form of land degradation, is reshaping terrestrial ecosystems worldwide. Although salinity is recognized as a strong environmental filter, its influence on bacterial and fungal communities remains insufficiently understood beyond taxonomic shifts. Here, we conducted a controlled irrigation experiment simulating salinity gradients to disentangle how diversity, network interactions, and assembly processes of bacteria and fungi respond to increasing salt stress. Results showed that high salinity significantly suppressed microbial richness, while mild salinity enhanced diversity, indicating a dual role of salinity as both stressor and structuring factor. Bacterial communities underwent pronounced taxonomic shifts, with halotolerant taxa dominating under high salinity, whereas fungal taxonomic composition remained relatively stable. Network analyses revealed that low salinity supported complex and resilient microbial networks, but high salinity simplified structures, reduced stability, and shifted keystone taxa toward tolerant groups. Fungal networks declined more sharply in connectivity than bacterial ones, reflecting higher vulnerability. Assembly process analyses demonstrated that bacteria, flexibly shifting under stress, while fungi were consistently governed by stochastic processes dominated by drift and dispersal limitation. These findings identify salinity thresholds as critical drivers of microbial ecological strategies and provide a mechanistic framework linking diversity loss, network fragility, and assembly shifts. Overall, our results reveals the differences of soil bacterial and fungal community construction under saline-alkali stress, providing an important theoretical basis for understanding the response of microorganisms to environmental changes and the ecological restoration of saline-alkali soils.