紫色土旱坡地土壤团聚体稳定性特征对侵蚀过程的影响

 【目的】研究紫色土旱坡地土壤团聚体稳定性特征及其对侵蚀过程的影响。【方法】利用野外人工模拟降雨与土壤团聚体特征分析的研究方法，对4种紫色土旱坡地土壤团聚体稳定性特征及其对侵蚀过程影响进行研究。【结果】（1）快速湿润使大部分团聚体崩解为细小的团聚体，慢速湿润和湿润振荡2种处理对5—2 mm大团聚体的影响最大，崩解后集中分布在2—0.5 mm范围内。（2）4种土地利用类型团聚体稳定性大小为桑园地＞苜蓿地＞荒草地＞菜地，快速湿润作用下4种土地利用类型团聚体的平均质量直径（MWD）和几何平均直径（GMD）都较小，慢速湿润处理的MWD和GMD总体较大，紫色土旱坡地土壤团聚体崩解机制主要是快速湿润时孔隙内封闭的空气压力作用，而黏粒膨胀对团聚体破坏的作用最小。（3）在持续模拟降雨下，4种旱坡地产流产沙量大小为：菜地＞荒草地＞苜蓿地＞桑园地，产流产沙过程与不同土地利用土壤团聚体稳定性特征相耦合；团聚体稳定性指标与产流率和产沙率在第1小时降雨历时相关系数大于第2 小时，快速湿润下MWD值分别和径流总量与侵蚀泥沙总量呈显著负相关，降雨侵蚀产沙过程中土壤团聚体孔隙内部空气压力对土壤团聚体的破碎是侵蚀产沙的主要形式。【结论】土壤团聚体稳定性越差，紫色土旱坡地侵蚀产沙量和径流量越大，降雨前期土壤团聚体稳定性特征与侵蚀产流产沙相关性最高，MWD能更好反映紫色土土壤团聚体与侵蚀产沙和产流间的关系，紫色土旱坡地土壤团聚体内部空气压力破坏是土壤团聚体破碎侵蚀产沙的主要形式。

Aggregate Stability of Purple Soil and Its Impacts on Soil Erosion of Slope Dry Land

【Objective】The objective of this research was to study the purple soil aggregate stability compared with soil erosion in different land use types of dry land.【Method】By using the methods of Simulated Rainfall and analysis characteristics of soil aggregates, the purple soil aggregate stability characteristics of four land use types and their impacts on the process of erosion were studied.【Result】It was found that fast wetting made the majority of aggregate breaking down to the small aggregates. The great impact of two treatments which were slow wetting and wet stirring was the 5-2 mm large aggregates which the diameter is mainly concentrated in 2-0.5 mm after collapse. The aggregate stability of four land types is mulberry plantation＞alfalfa＞grassland＞vegetable garden. Both the MWD and GMD are the smallest for four land use types of fast wetting, and the largest of the MWD and GMD are slow wetting. The mainly collapse mechanism of soil aggregates in purple soil dry land is fast wetting when the internal air pressure, and the minimal damage is clay swelling. The order of total runoff and sediment in four land use types under simulated rainfall is vegetable land＞grassland＞alfalfa＞mulberry plantation, and the process of runoff and sediment coupled with the aggregate characteristics of stability. The correlation of soil aggregate stability index between runoff rate and sediment yield rate of rainfall is high in the first 1 hour.
MWD values under fast wetting were significantly negatively correlated with runoff and sediment erosion. The mainly soil erosion of aggregate crushing mechanism of purple soil in dry land is soil aggregate destruction of the internal air pressure.【Conclusion】The worse the stability of soil aggregates, the more erosion and runoff in purple soil dry land. The relation between soil aggregate stability and sediment characteristics is the highest in antecedent rainfall erosion. It is better to use MWD to reflect the relationship between purple soil aggregates stability and erosion and runoff. The mainly soil erosion of aggregate crushing mechanism of purple soil in dry land is soil aggregate destruction of the internal air pressure.