| 其他摘要 | 【Objective】Soil organic matter is an important component of soil aggregate. Though much study has already been
done on its role and mechanism in the forming of soil aggregate, little is available in the literature about its effects on splash
erosion disintegrating soil aggregates and on contributions to the mechanical impact and slaking effect of raindrops disintegratingsoil aggregates, too. So more studies need to be done in this aspect. The purpose of this study is to explore effects of organic
matter content on breakdown of soil aggregates in splash erosion. 【Method】An indoor splash erosion experiment was conducted
in the State Key Laboratory of Dryland Farming and Soil Erosion on the Loess Plateau, Institute of Soil and Water Conservation,
Chinese, Academy of Sciences and Ministry of Water Resources, China. Soil samples different in soil organic matter content were
collected from Fuxian of Shanxi Province for test in the experiment, which was designed to have home-made needle nozzles to
simulate rainfalls of 95% alcohol solution and ultra-pure water, separately to distinguish effect of mechanical impact from slaking
effect of raindrops on soil aggregates. The nozzle setting was designed to have four levels of height, i.e. 0.5 m, 1 m, 1.5 m and 2
m for controlling strength of the impact of raindrops. 【Result】Results show that of the five soil samples different in soil organic
matter content, soil aggregate stability exhibited an order of MWD SW > MWD WS > MWD FW , indicating that the higher the content
of soil organic matter, the higher the stability of the soil aggregates and the higher the breakdown resistance of the soil. A
significant relationship was observed between the content of organic matter and the stability index of soil aggregates. In soils high
in organic matter content, the fraction of large aggregates (>0.25 mm) after the rainfall was approaching to that in proportion
before the rainfall with the organic matter content increasing. The amount of large aggregates was significantly higher in the soil
subjected with rainfall of alcohol than in the soil done with ultra-pure water. Splash erosion rate in all the five soils increased with
rising height of the nozzles or kinetic energy of raindrops, regardless of type of raindrops and their relationship could be described
with a power function. With rising kinetic energy of the rainfall, contribution rate of the slaking effect and mechanical impact
decreased and increased, respectively. Under raindrops the same in kinetic energy, contribution of the slaking effect decreases
with increasing organic matter content. 【Conclusion】 Increase in organic matter content enhances stability of the soil aggregates
and reduces contribution of the slaking effect in the process of splash erosion. All the findings in this study can serve as a
scientific basis for evaluation of stability of soil aggregates and exploration of factors disintegrating soil aggregates during the
process of splash erosion. |
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