Ferromanganese nodules (FMNs) are common products of pedogenesis and differ significantly from the surrounding soil matrix in terms of morphology, microstructure, and chemical composition. FMNs have direct impacts on nutrient cycles and heavy metal adsorption, and the concentric ring structure (or undifferentiated fabric) of FMNs can serve as fingerprints in assessing the paleoclimatic conditions and pedogenic environments. Despite the extensive research on the formation, characteristics and environmental implications of FMNs, little is done in terms of review highlights of the research achievements, gaps and future directions in this field. This paper reviewed and summarized the advances and achievements in the research of pedogenic FMNs, including i) formation mechanisms, evolution processes, and influencing factors of FMNs; ii) variations in micromorphology, elemental contents, and mineral compositions of FMNs in different soil types; and iii) sorption, substitution, and fixation of soil nutrients and heavy metals by FMNs. The areas of future studies included: i) determining the age, formation rate, and environmental threshold of FMNs at different stages of pedogenesis using numerical dating techniques; ii) establishing FMN evolution models for both natural and anthropogenic soils to better understand the complex changes of FMNs; and iii) clarifying the processes and mechanisms governing the fixation and re-activation of soil nutrients and heavy metals by FMNs via combined controlled experiments and isotope techniques. Addressing the above areas requires multidisciplinary collaborations, multi-analytical techniques and advanced isotope chronology. Clearly, the potential exists to vastly improve mechanistic understanding of FMN formation and evolution and the ways in which this can influence biogeochemical cycles.

锰铁结核(FMN) 是成土作用的常见产物，在形态、微观结构和化学成分方面与周围土壤基质有显着差异。FMNs对养分循环和重金属吸附有直接影响，FMNs的同心环结构（或未分化结构）可以作为评估古气候条件和成土环境的指纹。尽管对FMNs的形成、特征和环境影响进行了广泛的研究，但对该领域的研究成果、差距和未来方向的综述很少。本文回顾和总结了成因性FMNs的研究进展和成果，包括i) FMNs的形成机制、演化过程及影响因素；ii)不同土壤类型中 FMN 的微形态、元素含量和矿物组成的变化；iii) 吸附、替代和固定FMNs的土壤养分和重金属。未来研究的领域包括：i) 使用数值测年技术确定 FMN 在不同成土阶段的年龄、形成率和环境阈值；ii) 建立自然和人为土壤的 FMN 演化模型，以更好地了解 FMN 的复杂变化；iii) 通过联合控制实验和同位素技术，阐明 FMN 对土壤养分和重金属的固定和再活化的过程和机制. 解决上述领域需要多学科合作、多分析技术和先进的同位素年代学。显然，存在极大地提高对 FMN 形成和演化的机制理解以及这可能影响生物地球化学循环的方式的潜力。