自然降雨条件下结皮层团聚体稳定性变化特征研究

通过野外定位监测和室内分析相结合的方法,以三峡库区典型黄壤为研究对象,结合Le Bissonnais(LB)法中快速湿润(FW)、慢速湿润(SW)和预湿润振荡(WS)3种处理方法定量分析结皮层与表土层团聚体稳定性的差异。研究结果表明:在降雨作用下土壤团聚体稳定性存在较大的动态变化,结皮层团聚体稳定性在自然降雨作用下呈现波动式上升的趋势。FW、SW、WS处理下,结皮层土壤团聚体平均质量直径变化范围分别为0.73~2.13 mm、1.70~2.90 mm和2.27~3.16 mm,下层土壤在FW处理下团聚体稳定性呈波动式上升趋势,平均质量直径变化范围为0.70~1.27 mm,在SW和WS处理下呈略微下降趋势,其变化范围分别为1.69~2.83 mm和2.53~2.95 mm。在降雨影响下,土壤结皮与下层土壤团聚体稳定性存在较大的差异,随着降雨场次的增加,结皮层团聚体稳定性逐渐高于下层土壤,且两者差值逐渐增大。在土壤有机质、阳离子交换量、pH值等理化性质基本不变的情况下,土壤团聚体稳定性在自然降雨影响下也存在较大的动态变化。

Dynamics of Stability of Soil Crust under Natural Rainfall Event

Soil aggregate stability is a key parameter influencing soil fertility, environmental problems, and soil sensitivity to erosion. It is well established that aggregate stability changes over time. However, there is a lack of information considering the dynamics of aggregate at a short term step in the field. In addition, aggregate stability is usually determined by using soil samples collected from the plough layer, while soil erosion occurs in the surface soil. The difference between the soil crust and plough layer is usually ignored. The objectives were to investigate the variations in aggregate stability under rainfall event, identify the factors controlling these variations of stability, and compare the difference of aggregate stability between soil crust and subsurface soil. A field experiment was conducted on a cropland with typical yellow soil in Three Gorges Reservoir area. Sampling was performed after rainfall events. Aggregate stability was measured for both crust soil and subsurface soil by the Le Bissonnais (LB) method. Rainfall amount, rainfall intensity, air temperature, soil temperature and soil water content at the time of sampling were measured as potential explanatory factors. The results showed that aggregate stability varied significantly (P<0.05) under rainfall event for both the soil crust and subsurface soil. During the experiment, the mean weight diameter (MWD) obtained under fast wetting, slow wetting, and pre wetting shaking treatments was varied between 0.73mm and 2.13mm, 1.70mm and 2.90mm, and 2.27mm and 3.16mm, respectively, for the soil crust. While MWD of subsurface soil was varied between 0.70mm and 1.27mm, 1.69mm and 2.83mm, and 2.53mm and 2.95mm, respectively. Great differences between the aggregate stability of soil crust and subsurface soil were found. And the aggregate stability of soil crust was significantly higher than that of surface soil. For the soil crust, accumulative rainfall amount, rainfall intensity, air temperature, soil temperature and soil water content at the time of sampling greatly controlled the variations of aggregate stability in fast wetting and slow wetting treatments. The large differences in aggregate stability between soil crust and the plough layer implied large differences in soil erodibility. And the soil erodibility was varied greatly in the field over several rainfall events.