Declines in organic matter persistence with increased soil carbon.

Area of Science:

• Soil Science
• Biogeochemistry
• Climate Science

Background:

• Soil organic matter (SOM) persistence is key for carbon-climate feedback predictions.
• Understanding the relationship between soil organic carbon (SOC) and SOM persistence across environmental gradients is crucial but remains unclear.

Purpose of the Study:

• To investigate how increasing SOC content affects long-term SOM persistence.
• To analyze the influence of environmental gradients and microbial processes on SOC stabilization.

Main Methods:

• Analysis of soil radiocarbon, SOM physicochemical composition, and microbial carbon use efficiency (CUE).
• Data collected along a precipitation-driven gradient and integrated with global datasets.

Main Results:

• SOC persistence, indicated by radiocarbon signatures, declines as SOC content increases, both locally and globally.
• Higher SOC soils are dominated by younger, faster-cycling carbon.
• Increased plant carbon inputs correlate with decreased SOM persistence and younger SOC.

Conclusions:

• SOC content alone is insufficient to predict long-term soil carbon persistence.
• Plant carbon inputs and microbially mediated processes are critical factors influencing SOM stabilization.
• Earth system models need to incorporate these factors for accurate climate predictions.