A: PSD, pore size distribution; VPD, volume pore distribution.S S : M M Rainfall changes the physical state, pore system geometry, and structure of soils. Characteriza on of the soil pore system provides a realis c base to understand the reten on and movement of water in soil. The objec ve of this work was to es mate mul fractal parameters from Hg injec on porosimetry data on the uppermost soil surface layer as aff ected by simulated rainfall. Soil aggregates were sampled at the 0-to 2-cm depth in a loamy soil, both on a recently lled soil surface and on its disturbed counterpart a er 260-mm cumula ve rainfall. Pore size distribu ons (PSDs) were determined by Hg intrusion porosimetry from 0.005-to about 100-μm pore diameters on 10 samples per surface stage. The rainfall reduced aggregate pore volume, showing signifi cant diff erences between the pore space of the reference and the disturbed soil surfaces. A mul fractal analysis was performed by means of scaling of the moments ranging from −10 < q < 10 for all PSDs. Mean values of the entropy dimension, D 1 , and correla on dimension, D 2 , in the aggregate set sampled a er rain disturbance were lower than those of the reference stage; however, mean values of the diff erence Δ(D 1 − D 2 ), the Hölder exponent of order zero, α 0 , and widths of the le (α 0 − α q+ ) and right (α q− − α 0 ) hand sides of the singularity spectra f(α) a er rainfall ac on were higher than those of the ini al soil surface. Entropy dimension, D 1 , and the width of the le (α 0 − α q+ ) hand side of the f(α) spectra best discriminated between PSDs of the reference ini al soil surface vs. soil surface disturbed by rain.

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Multifractal analysis is now increasingly used to characterize soil properties as it may provide more information than a single fractal model. During the building of a large reservoir on the Parana River (Brazil), a highly weathered soil profile was excavated to a depth between 5 and 8 m. Excavation resulted in an abandoned area with saprolite materials and, in this area, an experimental field was established to assess the effectiveness of different soil rehabilitation treatments. The experimental design consisted of randomized blocks. The aim of this work was to characterize particle-size distributions of the saprolite material and use the information obtained to assess between-block variability. Particle-size distributions of the experimental plots were characterized by multifractal techniques. Ninety-six soil samples were analyzed routinely for particle-size distribution by laser diffractometry in a range of scales, varying from 0.390 to 2000 μm. Six different textural classes (USDA) were identified with a clay content ranging from 16.9% to 58.4%. Multifractal models described reasonably well the scaling properties of particle-size distributions of the saprolite material. This material exhibits a high entropy dimension, D 1 . Parameters derived from the left side (q N 0) of the f (α) spectra, D 1 , the correlation dimension (D 2 ) and the range (α 0 − α q+ ), as well as the total width of the spectra (α max − α min ), all showed dependence on the clay content. Sand, silt and clay contents were significantly different among treatments as a consequence of soil intrinsic variability. The D 1 and the Holder exponent of order zero, α 0 , were not significantly different between treatments; in contrast, D 2 and several fractal attributes describing the width of the f (α) spectra were significantly different between treatments. The only parameter showing significant differences between sampling depths was (α 0 − α q+ ). Scale independent fractal attributes may be useful for characterizing intrinsic particle-size distribution variability.

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