贡嘎山暗针叶林森林生态系统土壤水分运移特征分析

Movement characteristics analysis of soil water flow in the dark coniferous forest ecosystem of Gongga Mountain,Sichuan Province of southwestern China

开展优先流研究是土壤水运动机理研究由均质走向非均质领域的标志,可以有效解释早期水文学研究所困扰的不符合达西定律及对流--弥散方程等重大问题,但它在常规手段下难以获取。该文利用自制实验仪器,在研究区域开展室内土柱实验,系统分析研究区域土壤水分运移特征及优先流运移特征。结果表明:研究区域内4个演替阶段的土壤水分运动的壤中流过程主要表现为优先流,而土壤中的基质部分,则表现为不动区域。一旦优先流路径形成,土壤将不再阻拦水入渗,导致随后的降雨入渗穿过前面已经湿润并存在的优先流路径。优先流路径是研究区域水分在土壤中运移的主要途径,只要降雨雨强不停止,水将始终沿着优先流路径向下运移。运用综合染色示踪及影像分析技术对土柱出流液的流量、流速及通量数值进行分析,可以判断出研究区域的土壤优先流具有环绕特征和非平衡特征。

Research on preferential flow is involved with the mechanism of soil water movement from homogeneous to heterogeneous fields,and can answer a number of key questions that cannot be explained by Darcy's law and the Convective-Diffusive Equation in early hydrological researches.Experimental or technological analyses are difficult because this movement cannot be easily detected.The authors studied the characteristics of soil water flow and preferential flow of the fast water movement in the root zone,supported by a soil column experiment using homemade experimental apparatus in four successive stages(young,middle-aged,mature and over-mature).The results showed that preferential flow was the main type of soil water flow in the four successive stages,and the matrix part of the soil was an immobile area.Once the preferential flow path formed,soil was unable to hinder the penetration of water,which caused the following rain to infiltrate into the existing preferential flow path.The preferential flow path was the main route along which water moved downward until the rainfall stopped.It is judged through dying and image analysis technique that the preferential flow in the study area has surrounding characteristics.It is clear from numerical analyses of the water discharge,velocity and flux of soil column experiments that the preferential flow in the study area has unbalanced characteristics.