重庆四面山草地土壤大孔隙的数量和形态特征研究

Study on Number and Morphological Characteristics of Soil Macropores in Grass Land in Simian Mountain of Chongqing

以重庆四面山草地为研究对象，利用染色示踪法观察优先流的发生区域，采用水分穿透曲线和Poiseulle方程分析土壤大孔隙的数量、形态特征及其对优先流的影响。结果表明：研究地土壤剖面大孔隙呈现聚集态分布，孔径范围在0．3～2．2mm之间，其中半径大于1．3mm的大孔隙是优先流发生的主要通道。各孔径范围内染色区土壤大孔隙数量较未染色区高出1个数量级，大孔隙数量随土壤深度增加而减小，这样的分布特征有利于水压梯度的形成，有助于水分的快速垂直运移。染色区较非染色区有更大的稳定出流速率，约1．12～2．02倍，这得力于大孔隙数量和密度上的优势，这一优势极大地影响了优先路径分布和优先流发生。

In this study, dye tracing method was used to observe the occurrence of preferential flow region in the Simian Mountain＇s grass land. The number of soil macropores, morphological characteristics and their impact on preferential flow was obtained by Poiseulle equation and water breakthrough curves. The results showed that： Preferential flow occurs mainly in roots, worm holes and soil cracks with the aggregated distri- bution. The macropore diameter was in the range between 0.3-2.2 mm while the main channel of preferen- tial flow was above 1.3 mm. The number of macropores decreased gradually with the soil depth, this distri- bution of macropores contributed to the formation of pressure gradient, which resulted in the preferential vertical transport of water. Owing to the large quantity and high density of macropores, the steady effluent volume of dye-stained area was 1.12-2.02 times of dye-unstained area. The quantity and density of macro- pores was greatly affecting the formation of preferential flow.