Fractal characterization of soil particle size distribution under different land use patterns on the north slope of Wula Mountain in China

Purpose For thousands of years, humanity has been significantly altering the surface topography of the Earth in a measurable manner, and different land use practices have exerted substantial influence on soil structure and nutrient composition. This study aimed to assess the impact of various land use patterns on soil structure and physicochemical properties on the north slope of Wula Mountain, with a focus on seven land use modes in Urad Front Banner, Inner Mongolia, China.Materials and methods The tested soil samples were collected from seven land use patterns (cultivated land, artificial forestland, low-coverage grassland, medium-coverage grassland, artificial shrubland, sand dune, bare land). Soil particle sizes were measured by a Laser Particle Analyzer. Soil pH was measured using a pH meter, soil organic matter was determined by the potassium dichromate oxidation-external heating method, soil total nitrogen was measured using the Kjeldahl procedure, soil total phosphorus was analyzed using the acid dissolution-molybdenum antimony colorimetric method, and soil total potassium was assessed through the hydrofluoric acid digestion method. The fractal dimension values of soil PSDs were calculated using the volume-based single fractal model. Spearman correlation analysis was used to analyze whether different parameters used in the fractal model influenced the results of the fractal dimensions.Results and discussion Soil particle size analysis revealed that sand particles dominated, accounting for 57.01 to 90.95%, with loamy sandy soil and sandy loam soil being the predominant textures observed. The soil fractal dimension D (0-30 cm) showed a trend of dune (2.319) < artificial shrubland (2.434) < bare land (2.485)approximate to artificial forestland (2.485) < low-coverage grassland (2.515) < cultivated land (2.530) < medium-coverage grassland (2.531), and the correlation coefficients ranged from 0.854 to 0.956 (P < 0.01). The D values showed a significantly positive correlation with the clay, silt, soil organic matter, and soil total nitrogen contents and a strong negative correlation with the sand content and pH. Under different sampling depths, the highest fractal dimension (d) value is 2.6 (20-30 cm) for low-coverage grassland, while the lowest value is 2.298 (10-20 cm) for dune. These factors serve as important positive or negative indicators for assessing soil nutrients; the fractal dimension of soil has also been used to utilize as a statistical variable to evaluate changes in soil texture and fertility levels.Conclusion This study underscores the crucial role of land use patterns in shaping soil properties, emphasizing the significance of sustainable soil management. The fractal dimension of soil particles proves valuable for assessing fertility and texture, offering insights into sustainable land practices.