A Radiocarbon-Based Framework to Assess Soil Organic Carbon Persistence and Vulnerability Across Land-Use Types.

Area of Science:

• Soil Science
• Ecology
• Biogeochemistry

Background:

• Soil organic carbon (SOC) is crucial for soil health and climate regulation.
• Understanding SOC persistence and vulnerability is key to predicting carbon sequestration and loss under environmental change.
• Land use and environmental conditions significantly influence SOC stability.

Purpose of the Study:

• To investigate SOC persistence and vulnerability across five land-use types.
• To develop and apply a novel SOC vulnerability index.
• To identify key drivers of SOC stabilization and destabilization.

Main Methods:

• Combined radiocarbon dating (SOC system age, respired CO2 transit time) with biological and thermal stability indicators (SOC decomposability, residual oxidisable carbon content - ROC).
• Applied a vulnerability index across 19 sites representing diverse land-use types (grasslands, forests, croplands, peatlands) and soil depths.
• Analyzed relationships between SOC age, stability metrics, and land-use type.

Main Results:

• SOC ages varied significantly (2 to 5760 years) across land uses and depths, with transit times generally shorter than system ages.
• Organo-mineral stabilization enhanced SOC persistence in forests, temperate grasslands, and croplands.
• Alpine grasslands and peatlands exhibited long SOC ages despite low thermal stability, indicating vulnerability under changing conditions due to inhibited decomposition.

Conclusions:

• A combined approach using radiocarbon data and stability metrics effectively assesses SOC vulnerability.
• Land-use type and environmental conditions (temperature, moisture) are critical determinants of SOC persistence and potential loss.
• Managed peatlands and alpine grasslands represent significant carbon stores vulnerable to disturbance-induced release.