Microbial carbon use efficiency promotes global soil carbon storage.

Area of Science:

• Soil science
• Microbiology
• Ecology

Background:

• Soils are critical carbon sinks, but the mechanisms of soil organic carbon (SOC) formation and persistence are not fully understood.
• Soil microorganisms are recognized as important drivers of SOC dynamics, influencing its formation, preservation, and loss.
• Microbial carbon use efficiency (CUE) integrates microbial responses to carbon input and loss, offering potential as a predictor of SOC storage, yet its role in SOC persistence remains debated.

Approach:

• This study investigates the relationship between microbial CUE and SOC preservation using global datasets.
• A combination of a microbial-process explicit model, data assimilation, deep learning, and meta-analysis was employed.
• The research examined interactions between CUE and environmental factors including climate, vegetation, and soil properties.

Key Points:

• Microbial CUE was found to be over four times more influential than other factors (e.g., carbon input, decomposition) in determining global SOC storage.
• A positive correlation was observed between microbial CUE and SOC content across diverse global environments.
• The findings highlight CUE as a primary determinant of spatial variation in SOC storage worldwide.

Conclusions:

• Microbial carbon use efficiency is a critical, yet previously underestimated, factor controlling global soil organic carbon storage.
• Further understanding of microbial CUE and its environmental dependencies is essential for predicting soil carbon feedbacks under future climate scenarios.
• This research underscores the importance of microbial processes in regulating Earth's carbon cycle and climate system.