20 compared twenty-two soils with different textures and parent materials, where the results indicated that the relationship between fractal dimension and a soil’s specific surface area and cation exchange capacity can be well described by a second-degree polynomial regression model. 19 studied the plough layer of croplands and found the contents of organic carbon and total nitrogen had a positive correlation with the soil’s fractal dimension. Thus, the fractal dimension of a soil has a close relationship with these parameters. Differences in soil particle-size distribution affects the soil’s bulk density 10, 13, water movement 14, 15, 16, and soil nutrients 17, 18. Several studies have shown that the fractal dimension of the soil PSD was directly proportional to the silt and clay content, and inversely proportional to the sand content 7. Compared with traditional methods for characterizing soil particle-size distribution, fractal theory describes it well because it can characterize the local shape, size, structure and function of the material and any similarities between the part and the whole 10.įractal theory has been developed and widely used as a “bridge” for describing and quantifying the correlation between the distribution of soil particle-size and the physical and chemical attributes of soils. To date, fractal theory has been used to describe soil particle-size distribution, aggregate-size distribution, and pore-size distribution 12. 11 compared the volume-based and mass-based models, and found the former underestimated the clay content. The volume-based model has been widely used in particle size analysis, as the parameters and data required can be easily and accurately obtained using a laser particle-size analyser, thus allowing the assumption of the same density of soil particles of different sizes to be avoided 10. 9 developed a volume-based model to quantify the fractal dimension of PSD. However, with more comprehensive studies, the hypothesis of the same density of soil particles with different sizes has been questioned 8, 9. Following this, researchers have studied features of the fractal dimension of different soils and found that fractal theory was a useful tool for describing the soil particle-size distribution (PSD) and structure 6, 7. 5 developed a mass-based distribution model to calculate the fractal dimension of particle-size distribution. Early work by Turcotte 2 found that fractal concepts can be used as a measure of the fragility of fragmented material 2. At present, several researchers have explored different ways of analysing the fractal dimension of materials. Soil is a porous medium with a varied particle-size distribution as well as having irregular shapes and a self-similar structure, hence displaying fractal characteristics 3, 4. It is therefore possible to conclude that a soil’s fractal dimension could serve as a potential indicator of soil alkalization and the variability in alkaline soil texture.įractal geometry theory has been used to describe natural bodies and phenomena displaying complicated shapes and self-similar characteristics 1, 2. Strong linear relationships between fractal dimension and salt content ( P < 0.05), in particular a very significant positive relationship with HCO 3 − ( P < 0.01), also exist. Thus, soils with higher silt and clay content have higher fractal dimension values. A linear regression analysis showed a significant negative correlation between fractal dimension and the amount of coarse sand and fine sand (r = − 0.5452, P < 0.05 and r = − 0.8641, P < 0.01, respectively), and a significant positive correlation with silt and clay (r = 0.9726, P < 0.01 and r = 0.9526, P < 0.01, respectively). Our results show that the overall fractal dimension of the selected soils ranged from 2.35 to 2.60. Salt content, exchangeable sodium percentage, sodium adsorption ratio and other properties of the soils were determined and the soil particle-size distribution (0–2000 μm) was measured using a laser diffraction particle size analyser. Six soils with an increasing salinity (electrical conductivity was 0.09, 0.18, 0.62, 0.78, 1.57 and 1.99 dS m −1, respectively) were selected from the western part of the Songnen Plain (China). The purpose of this study was to identify the fractal dimension and their relationships with alkalinity properties of soils, and to evaluate the potential of fractal dimension as an indicator of alkalinity properties of soil.
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