Mechanisms of soil organic carbon stability and its response to no‐till: A global synthesis and perspective

• Published in: Global change biology Vol. 28; no. 3; pp. 693 - 710
• Main Authors: Kan, Zheng‐Rong, Liu, Wen‐Xuan, Liu, Wen‐Sheng, Lal, Rattan, Dang, Yash Pal, Zhao, Xin, Zhang, Hai‐Lin
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.02.2022
• Subjects: Agglomeration; Aggregates; Aggregation; Biological activity; Carbon; Carbon - metabolism; Carbon Cycle; Coordination compounds; Entrapment; Environmental effects; Metals; Microbial activity; Microorganisms; Mineralization; Minerals; Molecular structure; Organic carbon; Organic chemistry; Organic soils; Oxidants; Oxidizing agents; physicochemical protection; Priming; priming effects; Protection; Soil; Soil - chemistry; Soil moisture; soil organic matter; Soil properties; Soil stability; Soil stabilization; soil structure; Stability; Temperature; Tillage; tillage practices; priming effects; physicochemical protection; soil organic matter; microbial activity; soil structure; tillage practices
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.15968

Mechanisms of soil organic carbon (SOC) stabilization have been widely studied due to their relevance in the global carbon cycle. No‐till (NT) has been frequently adopted to sequester SOC; however, limited information is available regarding whether sequestered SOC will be stabilized for long term. Thus, we reviewed the mechanisms affecting SOC stability in NT systems, including the priming effects (PE), molecular structure of SOC, aggregate protection, association with soil minerals, microbial properties, and environmental effects. Although a more steady‐state molecular structure of SOC is observed in NT compared with conventional tillage (CT), SOC stability may depend more on physical and chemical protection. On average, NT improves macro‐aggregation by 32.7%, and lowers SOC mineralization in macro‐aggregates compared with CT. Chemical protection is also important due to the direct adsorption of organic molecules and the enhancement of aggregation by soil minerals. Higher microbial activity in NT could also produce binding agents to promote aggregation and the formation of metal‐oxidant organic complexes. Thus, microbial residues could be stabilized in soils over the long term through their attachment to mineral surfaces and entrapment of aggregates under NT. On average, NT reduces SOC mineralization by 18.8% and PE intensities after fresh carbon inputs by 21.0% compared with CT (p < .05). Although higher temperature sensitivity (Q10) is observed in NT due to greater Q10 in macro‐aggregates, an increase of soil moisture regime in NT could potentially constrain the improvement of Q10. This review improves process‐based understanding of the physical and chemical mechanism of protection that can act, independently or interactively, to enhance SOC preservation. It is concluded that SOC sequestered in NT systems is likely to be stabilized over the long term. Understanding the mechanisms of soil organic carbon (SOC) stability could be better to predict the SOC fate under climate change. Our review identified the factors affecting SOC stability and the roles of microbial residues in SOC stability regulated by physicochemical protection. This study provides systematic evidences of enhanced SOC accumulation under no‐till at upper soil depth, and improves process‐based understanding of the physical and chemical mechanisms of protection that can act, independently or interactively, to enhance SOC preservation. It is concluded that SOC sequestered in no‐till systems could be stabilized over the long term.