A review of advancements in the theory and characterization of soil macropore structure

Soil has an intricate pore structure, with the macropore structure serving as a pivotal component of gas exchange, liquid flow, and solute transport within the soil matrix. Scientifically understanding the macropore structure is important for the exploration of soil ecological functions. Drawing upon research literature from diverse nations, this study presents a comprehensive summary of past research findings, thoroughly examining the definition and taxonomy of soil macropores. Additionally, we delve into the factors that affect macropore structure, the effects of macropores on soil ecological functions, and the indicators that describe the nature of macropores. Furthermore, the principles, suitability conditions, benefits, and limitations of the widely utilized techniques for characterizing soil macropore structure were outlined, including staining observation, soil water retention curve, mercury intrusion porosimetry, gas adsorption, nuclear magnetic resonance, scanning electron microscopy, and computed tomography (CT). A comparative analysis was conducted to assist scholars in comprehending the theory of soil macropores, facilitating the selection of suitable macropore structure characterization techniques, and enabling the development of collaborative application modes among these techniques. Using the Web of Science core collection database, bibliometric software such as VOSviewer and CiteSpace were employed to explore the research hotspots and trends in CT, which is currently the most popular technique for characterizing soil macropore structure. This analysis offers insights into the future prospects of CT in the field of soil macropore structure characterization techniques. This article is of particular interest to readers engaged in the characterization of soil macropores.