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Background and Aims <p>Rhizosphere microbiomes are crucial for plant survival under edaphic stress, yet the mechanisms governing their niche differentiation and metabolic adaptation in degraded Mollisols remain poorly understood. This study investigates how poplar plantations (<i>Populus simonii</i> × <i>P. nigra</i>) regulate root-associated microbial assembly and metabolic profiles across a soil degradation gradient in Northeast China.</p> Methods <p>We analyzed microbial communities in the root endosphere, rhizosphere, and bulk soil using 16S rRNA and Internal Transcribed Spacer (ITS) amplicon sequencing, coupled with untargeted metabolomics.</p> Results <p>Soil degradation imposed a strong environmental filter, significantly reducing bacterial and fungal Shannon diversity in the bulk and rhizosphere soils by 18.3–29.7%. Strikingly, however, microbial diversity within the root endosphere increased by 12.6–21.4%, indicating a counter-intuitive host recruitment strategy. Bacterial assembly was primarily driven by available nitrogen and phosphorus (Mantel r &gt; 0.45), whereas fungal communities correlated more strongly with total carbon and phosphorus. Co-occurrence network revealed intensified competition in the rhizosphere (negative correlations &gt; 36%). Metabolomics identified 285 metabolites, characterized by a significant accumulation of lipid and fatty acid (VIP &gt; 1). These metabolic shifts strongly (|R|&gt; 0.6) correlations with key stress-tolerant taxa, including <i>Pseudomonas</i> and <i>Sphingomonas</i>.</p> Conclusion <p>These findings suggest that during early establishment, poplars employ an "insurance strategy" by actively expanding their endophytic diversity to buffer against degradation stress. The coupled accumulation of lipids and fatty acids reflects a composite signal of host stress adaptation and microbial turnover (necromass), rather than active nutrient cycling. This study highlights the importance of host-mediated microbial recruitment for plantation resilience in degraded ecosystems.</p>

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Divergent niche responses: poplar expands endophytic diversity and reconfigures rhizosphere metabolism in degraded Mollisols

  • 期刊论文

  • 发表日期：

    2026年4月18日

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  • Jia Yang,
  • Xiuwei Wang,
  • Huiyan Gu

摘要

Background and Aims

Rhizosphere microbiomes are crucial for plant survival under edaphic stress, yet the mechanisms governing their niche differentiation and metabolic adaptation in degraded Mollisols remain poorly understood. This study investigates how poplar plantations (Populus simonii × P. nigra) regulate root-associated microbial assembly and metabolic profiles across a soil degradation gradient in Northeast China.

Methods

We analyzed microbial communities in the root endosphere, rhizosphere, and bulk soil using 16S rRNA and Internal Transcribed Spacer (ITS) amplicon sequencing, coupled with untargeted metabolomics.

Results

Soil degradation imposed a strong environmental filter, significantly reducing bacterial and fungal Shannon diversity in the bulk and rhizosphere soils by 18.3–29.7%. Strikingly, however, microbial diversity within the root endosphere increased by 12.6–21.4%, indicating a counter-intuitive host recruitment strategy. Bacterial assembly was primarily driven by available nitrogen and phosphorus (Mantel r > 0.45), whereas fungal communities correlated more strongly with total carbon and phosphorus. Co-occurrence network revealed intensified competition in the rhizosphere (negative correlations > 36%). Metabolomics identified 285 metabolites, characterized by a significant accumulation of lipid and fatty acid (VIP > 1). These metabolic shifts strongly (|R|> 0.6) correlations with key stress-tolerant taxa, including Pseudomonas and Sphingomonas.

Conclusion

These findings suggest that during early establishment, poplars employ an "insurance strategy" by actively expanding their endophytic diversity to buffer against degradation stress. The coupled accumulation of lipids and fatty acids reflects a composite signal of host stress adaptation and microbial turnover (necromass), rather than active nutrient cycling. This study highlights the importance of host-mediated microbial recruitment for plantation resilience in degraded ecosystems.