5 CONCLUSIONS
This study found that the number of aggregates increased as the rainfall intensity increased, especially for the rainfall intensities of 68.61 and 217.26 mm h-1 (P < 0.05). The distribution of aggregate particles was affected by the original soil distribution and rainfall intensity, which decreased the number of 500-1000 μm aggregate particles and increased the number of < 500μm aggregate particles. The fractal dimension (FD) and specific surface area (SSA) increased significantly after raindrop splash (P < 0.05); as rainfall intensity increased, the FD and SSA values also increased. A greater degree of fragmentation led to a higher proportion of fine particles in the soil and more unstable soil aggregates. After raindrop splashing, especially from an intensity of 68.61 and 217.26 mm h-1, the microstructure of aggregates was denser than the undisturbed soil, and the average particle diameter of the aggregate decreased by 2.43%, 3.25% and 3.55%, respectively, compared with the undisturbed soil.
Aggregate breakdown was mainly caused by moderate to great rainfall intensities. The degree of fragmentation increased with the increase of raindrop diameter, rainfall intensity and rainfall energy, and more aggregate particles converted to finer particles. Consequently, these tiny particles intensified the pore clogging and infiltration weakening, exacerbated surface runoff and soil loss and reduced soil fertility; this process even accelerated the formation of surface crust and destroyed the soil structure. Therefore, to improve our understanding of the soil erosion process, synchrotron-based X-ray microcomputed tomography should be more widely used in the field of soil erosion, in combination with other methods, to study microstructure and soil aggregate fragmentation mechanisms.
CONFLICT OF INTEREST
There is no conflict of interest to declare.
ORCID
Li Guangluhttps://orcid.org/0000-0003-4107-8587