北京昌平区农地土壤大孔隙特征

研究在利用染色示踪法对北京昌平区农地的优先流发生区进行判断的基础上,采用Photoshop软件和土壤水分穿透曲线对该农地的大孔隙数量与分布特征进行量化分析。结果表明:试验农地的土壤大孔隙半径主要集中在0.5～2.8mm之间,平均半径为0.695～0.711mm,大孔隙率为5.10%～22.06%。随着土壤深度的增加,染色区在土壤剖面上呈现出集中分布的特征,同时,染色面积比例逐渐减小。各土层染色区的稳定出流速率是未染色区的1.39～2.05倍,在大孔隙各孔径范围内,染色区的数量是未染色区的1.33～3.57倍。大孔隙的垂直分布表现出上层多、下层少的特点,其中半径小于1.5mm的孔隙占98%以上。染色区在大孔隙密度、大孔隙连通性上的优势能够使其更快地进行水分运输并更早达到稳定,因而也就更易成为优先流发生区。

Macropores Properties of Agricultural Land at Changping District in Beijing

Based on the use of dyeing tracer method to estimate preferential flow occurrence on agricultural land at Changping district,Photoshop software and water breakthrough curves were used to make quantitative analysis on the number and distribution of soil macropores on the agricultural land in this study.The results showed that the radii of macropores were mainly massing between 0.5~2.8 mm,with average radii of 0.695~0.711 mm and macroporosity ranging from 5.10%~22.06%.With the increase in soil depth,dyeing area became more and more aggregated in soil profiles,while the square of the area decreased.The water steady effluent volume of dyeing area was 1.39~2.05 times of that of non-dyeing area with the difference of soil layers,and the number of dyeing area was 1.33~3.57 times of that of non-dyeing area with the difference of radii on the horizontal characteristics.The macropores showed a larger amount in upper layers and a smaller amount in lower layers on the vertical characteristics,and over 98% of these macropores were less than 1.5 mm in radius.Dyeing area has the advantage of macropore density and connectivity,which made water transport faster and stabilize earlier,that’s why preferential flow could occur in the area more often.