Mind the gap: non-biological processes contributing to soil CO2 efflux

Area of Science:

• Earth and Environmental Sciences
• Biogeochemistry
• Soil Science

Background:

• Soil CO2 efflux is a significant atmospheric CO2 source, with extensive research focusing on soil respiration.
• Current understanding often overlooks non-biological processes influencing CO2 production and transport in soils.

Purpose of the Study:

• To highlight deficiencies in current soil CO2 efflux research by examining less-studied production and transport processes.
• To emphasize the need for a comprehensive understanding of soil CO2 efflux for accurate global carbon budget modeling.

Main Methods:

• Review of existing literature on soil CO2 efflux, focusing on biological, pedochemical, and geological processes.
• Analysis of CO2 transport mechanisms beyond diffusion, including atmospheric pressure changes and thermal convection.
• Discussion of new and traditional measurement techniques for soil CO2 efflux.

Main Results:

• Soil CO2 efflux is influenced by biological (microbial decomposition, photodegradation) and non-biological (geothermal/volcanic degassing) processes.
• CO2 transport involves diffusion, atmospheric pressure changes, thermal convection, and lateral carbon fluxes, potentially leading to underestimation.
• Current measurement techniques may not fully capture all contributing factors to soil CO2 efflux.

Conclusions:

• A broader understanding of soil CO2 production and transport mechanisms, including non-biological factors, is essential.
• Standardized methods are needed to quantify diverse CO2 sources globally.
• Integrating biological and non-biological processes into biogeochemical models is critical for predicting climate change impacts on soil CO2 efflux.