Multifractal characterization of soil pore systems

Spatial arrangement of soil pores determines soil structure and is important to model soil processes. Geometric properties of individual pores can be estimated from thin sections, but there is no satisfactory method to quantify the complexity of their spatial arrangement. The objective of this work was to apply a multifractal technique to quantify properties of ten contrasting soil pore systems. Binary images (500 by 750 pixels, 74.2 mum pixel(-1)) were obtained from thin sections and analyzed to obtain f(alpha) spectra. Pore area and pore perimeter were measured from each image and used to estimate a shape factor for pores with area larger than 0.27 X 10(6) mum(2). Mean area of the lower (MA(L)) and upper (MA(U)) one-half of cumulative pore area distributions were calculated. Pore structures with large (MA(U) > 10 X 10(6) mum(2)) and elongated pores exhibited flat f(alpha)-spectra typical of homogenous systems (three soils). Massive type structure with small (MA(U) < 1 X 10(6) mu m(2)) rounded and irregular pores resulted in asymmetric f(alpha)-spectra (two soils). Well defined and symmetric f(alpha)-spectra were obtained with soil structures having elongated pores of intermediate size (1 X 10(6) < MA(U) < 10 X 10(6) mu m(2)) clustered around relatively small structural units (five soils). Multifractal parameters defining the maximum of the f(alpha)-spectra were correlated to total porosity (P < 0.001), and silt content (P < 0.05). This study demonstrates that the spatial arrangement of contrasting soil structures can be quantified and separated by the properties of their f(alpha)-spectra. Multifractal parameters quantifying spatial arrangement of soil pores could be used to improve classifications of soil structure.