Lacunarity of soil macropore space arrangement of CT images: Effect of soil management and depth

- Log-log lacunarity functions display linear, concave and sigmoid shapes.
- Representative elementary volume was attained in 81% of the cases.
- Linear and concave types dominate for tilt soil.
- Sigmoid type dominates on soil with a cover crop of natural vegetation.
- Ap and Bw horizons display different lacunar structures.

In this work we make use of 3D digital images of soil macropore space acquired by X-ray computed tomography of intact soil columns from a Mediterranean vineyard north of Spain to investigate how lacunarity describes soil structure. In the framework of fractal geometry, lacunarity can be seen as a test of fractal behavior and an alternative method to estimate fractal dimensions. From a wider perspective lacunarity provides insight into arbitrary spatial configurations. In this investigation, we consider different architectures of the dispersion and clustering of soil macropore space as deviations from the linear pattern of log-log lacunarity functions. We will explore how lacunarity quantifies different geometrical structures of soil macropore volumes and how these structures are affected by soil management and depth. We observed that, in the uppermost 15 cm of soil, treatment has an impact in the spatial arrangement of macropore space and that log-log lacunarity functions could display three different shapes that should be related to three different patterns of dispersion and clustering of macropore space. We also observed changes of soil macropore structure for samples up to a depth of 60 cm that could be described with the same three patterns of the log-log lacunarity functions found in the uppermost 15 cm of soil.