Soil Particle-size Distribution and Fractal Dimension of Different Land Use Types in Yingwugou Small Watershed of Dan River

There were 78 soil samples chosen in different profiles in Yingwugou watershed.Using fractal theory,the fractal features of soil particle-size distribution(PSD) under different types of land use,the spatial distribution of fractal dimension and the relationship between fractal dimension and soil nutrients were studied.The results indicated that:(1)The predominant soil particle sizes were found to be silt in studied area.The percentages of silt were between 45.41% and 66.19%.The contents of clay and gravel were relatively lower.(2)The soil fractal dimension of particle-size distribution could not be simulated by semi variance model and the Kriging simulation in small watershed.The soil fractal dimension in topsoil was largely affected by soil erosion.(3)The plots with thick soil and good conditions were often used as farmland under steep slope,causing the soil fractal dimension in the same slope to show: Farmland woodland and grassland.(4)The fractal dimension showed distinct difference according to the content of different particle-sizes.The fractal dimension of PSD had a strong positive correlation with silt-clay content,a negative correlation with the content of fine sand,coarse sand and gravel.(5)The fractal dimensions of cropland and grassland in 0-10 cm came to be smaller as the slope increased,but the slope showed a small influence on the fractal dimension of forest land.(6)The fractal dimension had strong positive relationship with soil water content in the four soil layers,but negative relationship with soil organic matter in 0-10 cm soil layer.