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利用北京密云水库上游的石匣坡面径流小区进行野外坡面产流产沙监测,探究坡地褐土土壤流失过程中土壤粒径组成变化及其影响因素。主要结论如下:坡面上部均发生土壤粗化现象。在坡度较大且无植被覆盖的坡面,坡上部土壤粗化程度强于坡中和坡下。雨季前土壤中粘粒和粉粒的含量最大,砂粒的含量最小;其次是雨季中,雨季后粘粒和粉粒的含量最小,砂粒的含量最大。在坡度较小且有植被覆盖的坡面,坡上部存在微弱的土壤粗化现象,坡下部表层土壤未现粗化。雨季前后,土壤中粘粒、粉粒和砂粒的含量变化均呈现相反的规律,即雨季前土壤粘粒、粉粒含量最小,砂粒的含量最大;而雨季后土壤粘粒、粉粒含量最大,砂粒的含量最小。随着降雨次数的增加,无论是与土壤分离的泥沙,还是坡面的产沙,粘粒含量均在减小,砂粒含量均在增多。降雨、坡度、坡长等均对泥沙起动产生促进影响,而植被覆盖会减弱土壤侵蚀和流失。
The runoff and sediment yield monitoring from the slope was carried out by using the calcareous slope runoff plot upstream of the Miyun Reservoir in Beijing to investigate the changes of soil particle size and its influencing factors in the process of soil loss on the cinnamon soil. The main conclusions are as follows: The phenomenon of soil coarsening occurred in the upper part of the slope. On the slope with larger slope and no vegetation cover, the soil roughness in the upper part of the slope is stronger than that in the slope and under the slope. Before the rainy season, the content of clay and silt in the soil was the largest and the content of sand was the lowest. The rainy season was followed by the smallest content of clay and silt and the highest content of sand. On the slopes with smaller slope and vegetation cover, there is a weak soil coarsening phenomenon in the upper part of the slope, and the surface soil in the lower part of the slope is not roughened. Before rainy season, the content of clay, silt and sand in the soil showed the opposite rule, that is, the soil clay and silt contents were the smallest before the rainy season, and the sand content was the largest. After the rainy season, the content of clay and silt was the largest, Grit content is the smallest. With the increase of rainfall number, both the sediment separated from the soil and the sediment produced on the slope, the clay content decreased and the content of sand increased. Rainfall, slope and slope length all have an impact on sediment start-up, while vegetation cover will reduce soil erosion and loss.