4.1 Effect of rainfall intensity on splashed soil aggregates
quantitative characteristics
The number of aggregate fragments increased corresponding to the
increase in rainfall intensity, especially at 68.61 and 217.26 mm
h-1 (Table 1). In the process of water erosion, the
primary mechanisms of aggregate breakdown are fast wetting and
mechanical breakdown caused by raindrop impact (Legout et al., 2005; Shi
et al., 2010). The results here show that, with an increase of rainfall
intensity, the quantity of aggregates and the degree of fragmentation
gradually increase.
In regards to aggregate distribution, aggregates mainly consisted of
250-500 μm, 106-250 μm, and <25 μm particle sizes, whereas for
volume, the 106-1000 μm range made up the majority (Fig. 3A and 3B).
Raindrop impact on the surface could affect soil erosion and alter
aggregate structure in various ways (Kinnell et al., 2005). When the
erosion process was dominated by rainfall detachment, the particle size
distribution of eroded soil was different from that of the original soil
(Slattery and Burt, 1997). It was affected by the particle distribution
of the original soil and the destruction of aggregates during erosion
(Mahmoodabadi et al., 2014). Based on the number and volume of aggregate
fragments, we found that raindrop splashing dispersed larger aggregate
particles (500-1000 μm) and broke them into aggregates of smaller
particles (<500 μm). Raindrop splashing changed the
arrangement of soil particles, decreased the number of larger aggregate
particles, and increased the quantity of smaller aggregate particles. As
a result, the particles formed by dispersion and fragmentation were
deposited in the pores of the upper soil, clogging the pores of the
topsoil and forming a thin, dense surface crust with low permeability
(Assouline, 2004). In turn, the crust further reduced soil infiltration
and exacerbated soil erosion (Sajjadi and Mahmoodabadi, 2015).