Morphology and multifractal characteristics of soil pores and their functional implication

Abstract

As an important inherentcondition for an eroded landform and fragile ecosystem, the erodible loess in China’s Loess Plateau is a clastic and predominantly silt-sized sediment. Understanding the pore complexity of the loess may be crucial for exploring soil functional properties and improving knowledge on hydrological dynamic processes occurring in the soil plant atmosphere continuum. Twelve undisturbed columns of four typical soil types, namely, aeolian sandy, light dark loessial, loessial, and Lou soils, were collected for the multifractal analysis of X-ray computed tomography images. The heterogeneity of soil pore distribution and the measure of porosity dispersion relative to the pore size dispersion in the loessial and Lou soils were significantly lower than those of the aeolian sandy and light dark loessial soils. The loessial soil exhibited the highest symmetry of singularity spectra and presented the lowest variability for pore arrangement. Most correlations among parameters of soil properties, multifractal characteristics, as well as soil macropore morphology and connectivity characteristics, were significant (p < 0.05 or 0.01). The multiple regression models of the theoretical saturated hydraulic conductivity and total porosity incorporated all types of the parameters, and the multifractal parameter ΔD was the dominant variable. Macropore connectivity parameters were commonly superior to the morphology ones when the links between macropore characteristics and multifractal parameters were considered. Meantime, the number of macropores acted as a crucial parameter influencing the complexity of soil pore structures. Overall, it is of great significance to integrate the soil pore complexity into the comprehensive understanding of pore function. This study also provides an effective reference for optimizing soil structures, improving the soil water holding capacity, and balancing the relationship between water and ecosystems in the Loess Plateau.