From energy to (soil organic) matter

Area of Science:

• Soil Science
• Microbiology
• Biogeochemistry

Background:

• Soil organic matter (SOM) is crucial for soil health and carbon sequestration.
• Current understanding of SOM formation often overlooks microbial energy dynamics.
• The role of energy transfer in SOM accumulation requires further investigation.

Purpose of the Study:

• To propose a novel perspective on soil organic matter formation.
• To elucidate the role of microbial energy utilization in SOM accumulation.
• To explain the energetic properties and ecological functions of SOM.

Main Methods:

• Conceptual analysis of microbial decomposition and energy transfer.
• Examination of the nominal oxidation state of carbon (NOSC) during decomposition.
• Integration of experimental data on litter decomposition and energy density.

Main Results:

• Microorganisms primarily use soil organics for energy, not carbon, leading to SOM accumulation as a byproduct.
• SOM becomes energetically enriched during decomposition due to preferential recycling of reduced compounds.
• SOM stores significantly more energy than litter, but its availability is lower, explaining its persistence.

Conclusions:

• SOM formation is driven by microbial energy investment exceeding energy gain, with SOM accumulating as a residual.
• Priming effects are driven by litter energy activating decomposers to access SOM nutrients.
• SOM acts as a nutrient store and energy flux mediator, with photosynthesis-derived energy being the primary driver of organic matter decomposition.