By Abbas Nazil
A new study by researchers from the Chinese Academy of Sciences has revealed that soil microorganisms influence carbon storage in ways that challenge long-held assumptions.
Soils globally store more carbon than the atmosphere and vegetation combined, making microbial activity a key factor in the global carbon cycle.
The study, published in Science Advances, examined the relationship between microbial carbon use efficiency (CUE) and heterotrophic respiration (Rh) across 1,094 observations from natural ecosystems worldwide.
CUE measures how efficiently microorganisms convert absorbed organic carbon into biomass, while Rh represents the rate at which microbes respire carbon dioxide back into the atmosphere.
High CUE microbes fix more carbon into soil organic matter, aiding sequestration, whereas low CUE microbes release more carbon, accelerating greenhouse gas emissions.
Traditional understanding assumed a linear decrease in CUE as Rh increased, but the study shows this relationship varies with ecosystem productivity.
In low-productivity regions such as arid or cold areas, CUE declines as Rh rises, consistent with previous assumptions.
However, in high-productivity ecosystems, including tropical and temperate zones, CUE stabilizes at approximately 0.27 once Rh exceeds 340 grams of carbon per square meter per year.
Researchers attribute this decoupling to microbial strategies that prioritize nutrient acquisition over carbon assimilation under resource-rich conditions.
In productive ecosystems, microbes expend energy obtaining limiting nutrients like nitrogen and phosphorus, which increases carbon release and limits additional soil carbon storage.
The findings suggest that vegetation greening may paradoxically accelerate soil carbon loss, while nutrient supplementation could enhance carbon sequestration.
The study emphasizes that ecosystem productivity drives a nonlinear relationship between microbial CUE and respiration, which has significant implications for climate models.
Incorporating microbial metabolic adaptability into carbon cycle models could improve projections of soil carbon storage and inform strategies to mitigate climate change.
Lead author Yongxing Cui and colleagues suggest that understanding microbial behavior is critical for accurately predicting carbon fluxes in diverse ecosystems worldwide.
The study provides a framework for integrating microbial ecological responses into global soil carbon assessments, offering a new perspective on climate change mitigation.
These insights underscore the importance of considering microbial community dynamics in soil management, restoration efforts, and global carbon accounting.
By refining predictions of carbon storage and release, the research highlights the central role of soil microbes in shaping Earth’s climate trajectory.
The findings may inform both policy and practical approaches to enhancing soil carbon sequestration across ecosystems, helping address climate change challenges.