Microbial dynamics and soil physicochemical properties explain large-scale variations in soil organic carbon

Area of Science:

• Soil Science
• Biogeochemistry
• Earth System Science

Background:

• Current Earth System Models (ESMs) rely on first-order decomposition models for carbon cycling projections.
• These models inadequately represent soil organic carbon (SOC) stabilization and climate change responses.
• Newer models require extensive in situ validation across diverse scales before ESM integration.

Purpose of the Study:

• To comprehensively evaluate the Microbial-MIneral Carbon Stabilization (MIMICS) model using extensive in situ data.
• To compare MIMICS' performance against the widely used CENTURY model for forest SOC dynamics.
• To assess MIMICS' capability in resolving SOC decomposition and stabilization mechanisms for climate change predictions.

Main Methods:

• Calibrated the MIMICS model using in situ observations of SOC, litterfall, and soil properties from 206 forest sites in Europe and China.
• Compared MIMICS simulations with the CENTURY model.
• Tested alternative process representations within MIMICS to refine physicochemical constraint hypotheses.

Main Results:

• MIMICS demonstrated superior accuracy in estimating forest SOC concentrations compared to CENTURY.
• MIMICS accurately predicted SOC sensitivity to soil temperature, clay content, and litter input.
• Model refinements reduced simulation errors, and MIMICS' microbial biomass to SOC ratios aligned with global observations.

Conclusions:

• MIMICS effectively captures key SOC decomposition and stabilization mechanisms.
• The model shows strong potential as a reliable tool for predicting terrestrial SOC dynamics under future climate change.
• MIMICS facilitates large-scale evaluation of evolving SOC formation and stabilization understanding.