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Background and Aims <p>Microbial carbon use efficiency (CUE) is a key parameter for predicting responses of the soil organic C (SOC) pool to environmental changes. Atmospheric sulfur (S) deposition has become a serious environmental concern and has triggered multiple adverse effects on grasslands. However, the effects of S deposition on soil microbial CUE and the key factors regulating it remain poorly understood in meadow steppes.</p> Methods <p>We conducted a 6-year simulated S deposition field experiment in a meadow steppe in China, and analyzed the response of microbial CUE to S addition. Plant traits, soil properties, bacterial community composition and extracellular enzyme activities were measured to clarify the main drivers.</p> Results <p>S addition caused soil acidification, which subsequently lowered soil nitrate-to-ammonium ratio and increased the grass-to-forb biomass ratio. The increased grass-to-forb ratio reduced soil C lability, which might be attributed to the deteriorated plant litter quality. The decreased soil C lability in combination with the declined nitrate-to-ammonium ratio promoted an oligotrophic soil condition, promoting a shift towards a K-selected microbial community, as indicated by low bacterial copiotroph-to-oligotroph ratios, average bacterial community rRNA operon copy numbers, and enzyme activities targeting labile substrates relative to recalcitrant compounds. Ultimately, the prevalence of microbial K-strategy contributes to an increase in microbial CUE with S addition.</p> Conclusion <p>Our findings highlight the importance of microbial ecological strategies in regulating CUE and would improve predictions of SOC dynamics under elevated S deposition in meadow steppes.</p>

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Sulfur addition enhances microbial carbon use efficiency by promoting the dominance of microbial K-strategy in a meadow steppe

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Changming Lu,
  • Zhirui Wang,
  • Mikhail V. Semenov,
  • Tianpeng Li,
  • Xue Feng,
  • Ning Dang,
  • Heyong Liu,
  • Jiangping Cai,
  • Wentao Luo,
  • Yong Jiang,
  • Irina Kravchenko,
  • Hui Li

摘要

Background and Aims

Microbial carbon use efficiency (CUE) is a key parameter for predicting responses of the soil organic C (SOC) pool to environmental changes. Atmospheric sulfur (S) deposition has become a serious environmental concern and has triggered multiple adverse effects on grasslands. However, the effects of S deposition on soil microbial CUE and the key factors regulating it remain poorly understood in meadow steppes.

Methods

We conducted a 6-year simulated S deposition field experiment in a meadow steppe in China, and analyzed the response of microbial CUE to S addition. Plant traits, soil properties, bacterial community composition and extracellular enzyme activities were measured to clarify the main drivers.

Results

S addition caused soil acidification, which subsequently lowered soil nitrate-to-ammonium ratio and increased the grass-to-forb biomass ratio. The increased grass-to-forb ratio reduced soil C lability, which might be attributed to the deteriorated plant litter quality. The decreased soil C lability in combination with the declined nitrate-to-ammonium ratio promoted an oligotrophic soil condition, promoting a shift towards a K-selected microbial community, as indicated by low bacterial copiotroph-to-oligotroph ratios, average bacterial community rRNA operon copy numbers, and enzyme activities targeting labile substrates relative to recalcitrant compounds. Ultimately, the prevalence of microbial K-strategy contributes to an increase in microbial CUE with S addition.

Conclusion

Our findings highlight the importance of microbial ecological strategies in regulating CUE and would improve predictions of SOC dynamics under elevated S deposition in meadow steppes.