Microcharacteristics of soil pores after raindrop action

Aggregate breakdown and transportation caused by raindrops clogs soil pores and aggravates the formation of surface crusts. However, changes in soil pore microcharacteristics after raindrop impact are equivocal. In this research, we used synchrotron-based X-ray microcomputed tomography (SR-mu CT) and image processing techniques to quantitatively analyze the pore microcharacteristics of undisturbed soil and disturbed soil impacted by raindrop diameters of 2.67 mm (small), 3.39 mm (medium), and 4.05 mm (large). The results showed that the changes in the soil pore microcharacteristics were mainly caused by medium and large raindrops. Compared with the undisturbed soil, the total imaged porosity decreased by 5.91% after splashing by small raindrops and significantly (P < .05) decreased by 15.83 and 18.28% after medium and large raindrop splashing, respectively. The total volume of pores and the porosity of the large pores had the same decreasing trend as the total porosity. The porosity of the elongated pores decreased by 11.51 and 23.41% after medium and large raindrop splashing, respectively. The raindrop action clogged the soil pores. The clogging ratios caused by small, medium, and large raindrops were 1.06, 2.83, and 3.29%, respectively, and increased with raindrop diameter, rain intensity, and rainfall energy. Thus the increase in pore clogging and the decrease in macroporosity are the main reasons for the formation of surface crusts.