Fractal characteristics of soil particle size in loess hilly areas with different years of conversion

The purpose of this study was to investigate the change of soil particle composition and its effect on the fractal dimension of grassland under different years of conversion. The changes of soil particle composition and soil fractal dimension were analyzed by taking the 8-year grassland and 31-year grassland in the Yuanzegou watershed of the loess hilly region as the research objects, and taking the sloping farmland as the control. The results showed that the clay content of soil was increased by 69.6%, 47.6% and 8.80%, 8.7%, respectively, in the 31-year grassland and the 8-year grassland in the 0-20cm, 20-40cm. The decrease of sand content was 38.7%, 18.2% and 15.6%, and 13.5%, respectively, which were significantly different from that of the 31-years grassland (P<0.05). The contents of particles in the 40∼60cm soil layer did not change significantly. fractal dimension range from 2.6 to 2.7, the expression for the conversion of 31 years grassland>grassland>changing slope farmland 8 years, the fractal dimension of soil particles increased along with the increasing length of the grass farmland, in 0∼20, 20∼40cm soil layer, the conversion of 31 years grassland soil particles fractal dimension D and slope have significant difference (P<0.05). The fractal dimension of soil particle volume was positively correlated with soil clay (P<0.01), and positively correlated with soil particle size on farmland and grassland after 31 years of conversion (R2=0.6970, 0.6701), but not on grassland after 8 years of conversion. There was a negative correlation between soil sand content and fractal dimension of soil particles in the three plots, but there was only a significant difference in slope farmland.