Multifractal Characteristics of Soil Particle Size Distribution and Effect of Biological Soil Crusts on Multifractal Spectrum

Soil particle-size distribution (PSD) is one of the most important physical attributes due to its great influence on soil physical, chemical, and biological properties. Water infiltration rate, land-use change, soil erosion, and biological soil crusts (BSCs) may influence PSD in a soil. The multifractal measures were useful tools in characterization of PSD in soils. The objective of the current study was to investigate the effect of BSCs on multifractal spectrum of soils. To this end, sixteen soil samples were collected from 0-5 cm and 5-15 cm depths in soils with and without BSCs in Qara Qir rangeland, north of Agh Ghala city of Golestan province, Iran. Particle size distribution was measured by the hydrometer method. Results showed that soils PSD had multifractal behavior. Multifractal spectra followed the typical sigmoidal shape. The result showed that fractal dimensions (i.e. D₀.₅, D₁, D_1.5, and D₂) were significantly positively correlated with clay content and significantly negatively correlated with sand content. In the current study, the (D₀ –D₂) index was used for investigation of multifractality. The average largest D₀ –D₂ was obtained at 0-5 cm depth of soil with BSCs (0.295) and average smallest D0 –D2 was obtained at 5-15 cm soil depth of soil without BSCs (0.240). Results showed that PSD of soils with BSCs had higher multifractality compared to those of soils without BSCs.