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Background and aims <p>Mineral-associated organic carbon (MAOC) is a relatively persistent soil carbon pool protected by minerals, with microbial necromass carbon (MNC) and plant-derived carbon (PDC) contributing through <i>in vivo</i> turnover and <i>ex vivo</i> modification, respectively. How those pathways and their governing mechanisms change along climate and soil depth gradients remains unresolved.</p> Methods <p>We collected topsoil (0–30&#xa0;cm) and subsoil (30–60&#xa0;cm) along three elevation gradients, quantifying MNC and PDC within MAOC via biomarkers, and characterizing microbial properties via enzyme activities and high-throughput sequencing.</p> Results <p>MNC and PDC increased significantly with elevation but declined with depth. MNC dominated MAOC (33.12% vs. 2.98% for PDC), and its contribution increased with elevation, indicating that <i>in vivo</i> turnover was more responsive than <i>ex vivo</i> modification to elevation-associated environmental changes. Responses were stronger in topsoil: MNC increased by 484.00% from low to high elevation in topsoil (vs. 235.44% in subsoil), while PDC increased significantly only in topsoil (+ 303.77%). Contrasting depth-dependent controls emerged: in topsoil, increased nutrient availability and decreased pH enhanced extracellular enzyme activity, a critical predictor of MNC and PDC accumulation; in resource-limited subsoil, microbial community diversity and composition governed their accumulation.</p> Conclusion <p>MNC exhibited stronger responses to elevation than PDC, highlighting the priority of <i>in vivo</i> turnover pathway under environmental changes. MNC and PDC responded more strongly to environmental changes in topsoil than subsoil, governed by contrasting microbial mechanisms. Collectively, our study improves understanding of persistent soil carbon dynamics and provides information for predicting their responses to environmental changes across soil profiles.</p>

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Microbial necromass dominates over plant-derived carbon in mineral-associated organic carbon accumulation with elevation: Depth-dependent shift from enzymatic to community control

  • 期刊论文

  • 发表日期：

    2026年7月30日

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  • Yuqi Wei,
  • Shiqi Zhang,
  • Qianru Ren,
  • Jinxian Liu,
  • Zhengming Luo,
  • Baofeng Chai

摘要

Background and aims

Mineral-associated organic carbon (MAOC) is a relatively persistent soil carbon pool protected by minerals, with microbial necromass carbon (MNC) and plant-derived carbon (PDC) contributing through in vivo turnover and ex vivo modification, respectively. How those pathways and their governing mechanisms change along climate and soil depth gradients remains unresolved.

Methods

We collected topsoil (0–30 cm) and subsoil (30–60 cm) along three elevation gradients, quantifying MNC and PDC within MAOC via biomarkers, and characterizing microbial properties via enzyme activities and high-throughput sequencing.

Results

MNC and PDC increased significantly with elevation but declined with depth. MNC dominated MAOC (33.12% vs. 2.98% for PDC), and its contribution increased with elevation, indicating that in vivo turnover was more responsive than ex vivo modification to elevation-associated environmental changes. Responses were stronger in topsoil: MNC increased by 484.00% from low to high elevation in topsoil (vs. 235.44% in subsoil), while PDC increased significantly only in topsoil (+ 303.77%). Contrasting depth-dependent controls emerged: in topsoil, increased nutrient availability and decreased pH enhanced extracellular enzyme activity, a critical predictor of MNC and PDC accumulation; in resource-limited subsoil, microbial community diversity and composition governed their accumulation.

Conclusion

MNC exhibited stronger responses to elevation than PDC, highlighting the priority of in vivo turnover pathway under environmental changes. MNC and PDC responded more strongly to environmental changes in topsoil than subsoil, governed by contrasting microbial mechanisms. Collectively, our study improves understanding of persistent soil carbon dynamics and provides information for predicting their responses to environmental changes across soil profiles.