Raindrop Energy Impact on the Distribution Characteristics of Splash Aggregates of Cultivated Dark Loessial Cores

Abstract

To determine the effect of different rainfall energy levels on the breakdown of soil aggregates, this study analyzed the soil splash erosion amounts and the distribution of particle sizes under six rainfall conditions (rainfall energy: 2.41 × 10−5–22.4 × 10−5 J m−2 s−1 and 1.29 × 10−4 J m−2 s−1) at five splash distances (from 0–10 cm to 40–50 cm). Cores of the size 10 × 20 cm of undisturbed cultivated dark loessial soil were selected in tree replicates as the research subject. The results indicated that splashed aggregates were distributed mainly at splash distances of 0–20 cm, which accounted for 66%–90% of the total splash erosion amount. The splash erosion amount significantly decreased exponentially with increasing splash distance for the same rainfall energy (p < 0.01). The splash erosion amount significantly increased in the power function relationship with increasing rainfall energy at the same splash distance (p < 0.05). A model was obtained to predict the splash erosion amount for rainfall energy and splash distance. The fractal dimension (D) of the aggregates showed a downward opening parabolic relationship with raindrop energy. The maximal value of the rainfall energy was 1.286 × 10−4 J m−2 s−1, which broke the aggregates to the largest degree. Enrichment ratio (ER) values for fragments >2 mm were close to 0. A particle size of 0.25 mm was the critical particle level for splash erosion.

Experimental Setup for Splash Erosion Monitoring—Study of Silty Loam Splash Characteristics

“…We have not done this analysis as we were not able to collect the undisturbed splashed soil aggregates. For example, Fu et al [13] show that especially the fine particle and aggregate (<0.053 mm) ratios change with variable rainfall KE. The KE per mm of rainfall is the same for all the measured points shown in Figure 8, which is due to the design of the rainfall simulator.…”

“…The transport splash distance increases with decreasing soil particle size. Fu et al [13] added that the splashed distance is not only related to particle or aggregate sizes, but also to rainfall kinetic energy.…”

Microcharacteristics of soil pores after raindrop action

“…Li et al (2018) investigated the relationship between raindrop diameter and aggregate fragmentation from a microscopic perspective via SR-μCT and analyzed the microscopic morphologic characteristics of soil aggregates before and after raindrop impact. Although many researchers have conducted extensive research on soil aggregates during water erosion (Amézketa, Singer, & Le Bissonnais, 1996;Le Bissonnais, 2010;Legout et al, 2005;Fu et al, 2016Fu et al, , 2019, they have mainly investigated the particle size distribution characteristics of split aggregates after splash erosion from a macroscopic perspective. Additionally, many studies on the application of SR-μCT scanning to soil aggregates and pores from a microscopic perspective have been carried out successfully.…”

Rainfall Erosivity in Soil Erosion Processes

“…The Special Issue contains four articles with a focus on hydrological hazards across China and Central Asia, dealing with: (1) spatiotemporal patterns of rainfall erosivity (Gu et al [8]), (2) the explanatory power of peak rainfall amounts on sediment yield (Xu et al [9]), (3) climate-change-induced rainfall erosivity (Duulatov et al [10]), and (4) rainfall energy-induced soil splash erosion (Fu et al [11]). The Tibetan Plateau (the focus of Gu et al [8]), the most active geological belt in China, is not only being affected by the melting of glaciers and other ice formations but also by heavy precipitations that provoke widespread soil loss.…”

“…This contribution is worthy because the researches on rainfall affecting runoff and sediment yield rarely analyze impacts from the point of view of rain peak morphology. Fu et al [11] clarified the effect of raindrop energy on the splash distance and particle size distribution of aggregate splash erosion and introduced a modelling approach to predict splash erosion in the Loess Plateau (central China). Duulatov et al [10] estimated the potential influence of climate change on erosivity precipitations over Central Asia.…”