Volume fractal dimension of soil particles and relationships with soil physical-chemical properties and plant species diversity in an alpine grassland under different disturbance degrees

Fractal geometry is an important method in soil science, and many studies have used fractal theory to examine soil properties and the relationships with other eco-environmental factors. However, there have been few studies examining soil particle volume fractal dimension in alpine grasslands. To study the volume fractal dimension of soil particles (D) and its relationships with soil salt, soil nutrient and plant species diversity, we conducted an experiment on an alpine grassland under different disturbance degrees: non-disturbance (N-0), light disturbance (L), moderate disturbance (M) and heavy disturbance (H). The results showed that (1) Ds varied from 2.573 to 2.635 among the different disturbance degrees and increased with increasing degrees of disturbance. (2) Shannon-Wiener diversity index, Pielou's evenness index and Margalef richness index reached their highest values at the M degree, indicating that moderate disturbance is beneficial to the increase of plant species diversity. (3) In the L and M degrees, there was a significant positive correlation between D and clay content and a significant negative correlation between D and soil organic matter (SOM). In the H degree, D was significantly and positively correlated with total salt (TS). The results suggested that to a certain extent, D can be used to characterize the uniformity of soil texture in addition to soil fertility characteristics. (4) For the L degree, there was a significant negative correlation between D and the Shannon-Wiener diversity index; while for the M degree, there was a significant negative correlation between D and Pielou's evenness index.