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<p>Soil carbon is the largest terrestrial carbon reservoir, critical in mitigating global climate change. Despite the alarming rise in global temperature, the influence of warming on multiple aspects of soil carbon remains uncertain. This study investigated the influence of warming on soil organic carbon (SOC) and soil microbial biomass carbon (SMBC) using the meta-analysis approach based on 117 global studies. Our analysis revealed critical thresholds controlling soil carbon vulnerability: Warming reduced SOC content and stock by 12.2% and 13.0%, respectively, but these effects occurred only when warming exceeded the 2&#xa0;°C threshold and lasted longer than the 3-year duration threshold. Similarly, while warming generally reduced SMBC (the active carbon fraction), its negative impacts were constrained by these same temperature and time thresholds. A depth-dependent threshold further modulated responses: Warming decreased SOC and SMBC in topsoil (≤ 20-cm depth threshold), whereas it increased them in subsoil (&gt; 20&#xa0;cm). Notably, the SMBC/SOC ratio increased across all conditions, suggesting SOC composition changes within these threshold boundaries. Further, the effects of warming on soil carbon were unchanged by ecosystem type or background climates, indicating a consistent response of soil carbon to warming globally. This study establishes triple thresholds (magnitude-duration-depth) that govern soil carbon sensitivity to warming, crucial for predicting carbon–climate feedbacks in a warmer world.</p>

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Critical Thresholds of Warming Magnitude, Duration, and Soil Depth Control Soil Carbon Vulnerability

  • 期刊论文

  • 发表日期：

    2025年10月20日

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  • Yuan Sun,
  • Shangtao Jiang,
  • Yan Zhou,
  • Xiaoming Zou,
  • Xinli Chen

摘要

Soil carbon is the largest terrestrial carbon reservoir, critical in mitigating global climate change. Despite the alarming rise in global temperature, the influence of warming on multiple aspects of soil carbon remains uncertain. This study investigated the influence of warming on soil organic carbon (SOC) and soil microbial biomass carbon (SMBC) using the meta-analysis approach based on 117 global studies. Our analysis revealed critical thresholds controlling soil carbon vulnerability: Warming reduced SOC content and stock by 12.2% and 13.0%, respectively, but these effects occurred only when warming exceeded the 2 °C threshold and lasted longer than the 3-year duration threshold. Similarly, while warming generally reduced SMBC (the active carbon fraction), its negative impacts were constrained by these same temperature and time thresholds. A depth-dependent threshold further modulated responses: Warming decreased SOC and SMBC in topsoil (≤ 20-cm depth threshold), whereas it increased them in subsoil (> 20 cm). Notably, the SMBC/SOC ratio increased across all conditions, suggesting SOC composition changes within these threshold boundaries. Further, the effects of warming on soil carbon were unchanged by ecosystem type or background climates, indicating a consistent response of soil carbon to warming globally. This study establishes triple thresholds (magnitude-duration-depth) that govern soil carbon sensitivity to warming, crucial for predicting carbon–climate feedbacks in a warmer world.