Three‐Dimensional Quantification of Macropore Networks in Undisturbed Soil Cores

Abstract

The role of macropores in soil and water processes has motivated many researchers to describe their sizes and shapes. Several approaches have been developed to characterize macroporosity, such as the use of tension infiltrometers, breakthrough curve techniques, image‐analysis of sections of soils, and CAT scanning. Until now, efforts to describe macropores in quantitative terms have been concentrated on their two‐dimensional (2‐D) geometry. The objective of this study is to nondestructively quantify the three‐dimensional (3‐D) properties of soil macropores in four large undisturbed soil columns. The geometry and topology of macropore networks were determined using CAT scanning and 3‐D reconstruction techniques. Our results suggest that the numerical density of macropores varies between 13421 to 23562 networks/m3 of sandy loam soil. The majority of the macropore networks had a length of 40 mm, a volume of 60 mm3, and a wall area of 175 mm2 It was found that the greater the length of networks, the greater the hydraulic radius. The inclination of the networks ranged from vertical to an angle of ≈55° from vertical. Results for tortuosity indicated that most macropore networks had a 3‐D tortuous length 15% greater than the distance between their extremities. More than 60% of the networks were made up of four branches. For Column 1, it was found that 82% of the networks had zero connectivity. This implies that more than 4/5 of the macropore networks were composed of only one independent path between any two points within the pore space.

A review of model applications for structured soils: a) Water flow and tracer transport

“…However, CT was insufficient to separate fast and slow flow domains in the fine sand columns, where this supplementary information could be provided by MRI and dye tracer distribution. Perret et al (1999) used CT for establishing the 3D arrangement of the geometry and topology of macropores. Perret et al (2000) further applied CT for real-time examination of Potassium iodide movement through the macropores and matrix of a large undisturbed soil column.…”

“…intact dry soil columns, 3D reconstruction of macropore networks, solute breakthrough analysis in space and time (Perret et al, 1999(Perret et al, , 2000 UC 3D hydraulic property distribution and diffusivity 3D hydraulic tomography by inversion of travel times of transient pressure propagation and diffusivity measured in hydraulic and pneumatic tests in unsaturated fractured sandstone core. UC θ(h) dependency on micromorphology Micromorphology of soil pore structure was studied on thin sections.…”

Carbon management in dryland agricultural systems. A review

“…The accumulation of C in the soil surface (i.e., C stratification) as a consequence of the use of different agricultural practices (e.g., no-tillage, biochar addition) usually improves water infiltration and saturated hydraulic conductivity (Franzluebbers 2002;Jordán et al 2010). Recent advances in X-ray computed tomography are increasing our knowledge about soil structure and the impacts of agricultural management on soil macroporosity (Perret et al 1999). Other tools such as the measurement of soil sorptivity are used to assess the potential of soil to capture rainfall (Shaver et al 2013).…”

Disaggregation and scientific visualization of earthscapes considering trends and spatial dependence structures

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