Microstructure changes of red clay during its loss and leakage in the karst rocky desertification area

Karst rocky desertification is a unique type of desertification caused by unreasonable human activities in a vulnerable ecological environment. It has severely restrained the sustainable development of Southwest China. Chenqi village which is the studied area in this paper has suffered karst rocky desertification for decades. Red clay samples were collected from different sites around this village and analyzed through mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests. Then, the microstructure changes of soil during its loss and leakage were observed to study the impact of rainfall erosion and the mechanism of soil loss and leakage. The results demonstrate that the land use patterns can change the distribution of micro/small pores in soil. The shrub grass land, which is least exploited by human activities, has the largest volume of micro/small pores. Meanwhile, soil leakage can change the distribution of medium/large pores. The soil from surface (0–15 cm), which is deposited at the beginning of soil leakage, has the largest volume of medium/large pores. Pore surface fractural dimension is negatively correlated with human activity impact, and positively correlated with the distribution of micro and small pores. The microstructure can well represent different phases of soil loss and leakage as well as the soil breakage level.