Influence of soil macropore structure on saturated hydraulic conductivity
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摘要:
目的 探究土壤不同孔径大孔隙结构特征及数量对土壤饱和导水率的影响，为研究区域土壤水分—溶质迁移规律、水土流失治理与土壤污染防治提供理论参考。 方法 以京郊密云水库五座山林场水源涵养林为研究点，基于工业CT扫描技术，对土柱中土壤大孔隙三维空间结构重建后，探究不同孔径大孔隙结构特征参数密度及数量密度对土壤饱和导水率的影响。 结果 （1）除当量孔径大于4.30 mm以外的大孔隙，当量孔径越大，其数量密度越小，结构特征参数密度越小；（2）6个样地3个土层内当量孔径为0.31 ~ 2.30 mm的大孔隙占所有孔隙的比例均高于95%；（3）样地1、2、5和6中饱和导水率最大的均在0 ~ 10 cm土层，且除样地6外，均随深度增大而减小，样地4的饱和导水率随深度增大而增大；（4）除当量孔径大于4.30 mm的大孔隙体积密度外，5个径级所有其他的大孔隙特征值密度均与饱和导水率呈显著正相关。 结论 （1）在0 ~ 30 cm土层内，大部分样地的饱和导水率随土层深度增加而减小，但也会出现随深度增加而增大的情况；（2）林地土壤的大孔隙当量孔径主要集中在0.31 ~ 2.30 mm，其占有率高达95%；（3）当量孔径越小的大孔隙，除大孔隙体积和表面积外的大孔隙结构特征参数密度越大；（4）除当量孔径 > 4.30 mm的大孔隙体积密度以外的大孔隙特征参数与饱和导水率均呈显著正相关，大孔隙数量对饱和导水率的影响要显著大于大孔隙结构参数。 Abstract:Objective This paper aims to explore the influence of structure and quantity of macropores with different diameter classes on the saturated hydraulic conductivity of soil, and to provide a theoretical reference for the study of soil water solute transport law, soil erosion control and soil pollution control in this area. Method The study was carried out on water conservation forest in Wuzuoshan Forest Farm of Miyun Reservoir in Beijing suburb. Based on the industrial CT scanning technology, the three-dimensional spatial structure of soil macropores in the soil column was reconstructed to explore the influence of structural parameter density and quantity density of macropores with different diameter classes on the soil saturated hydraulic conductivity. Result (1) Excepting for equivalent diameter large than 4.30 mm, the larger the equivalent diameter of macropores was, the smaller the quantity density and structural parameter density of macropores were. (2) In three soil layers of six sample plots, the proportion of macropores with an equivalent diameter of 0.31−2.30 mm to all macropores was higher than 95%. (3) The maximum saturated hydraulic conductivity of sample plot 1, 2, 5 and 6 was in 0−10 cm soil layer, and it decreased with the increase of soil depth, but except for sample plot 6. The saturated hydraulic conductivity of sample plot 4 increased with the soil depth increasing. (4) Except for the volume density of macropores with an equivalent diameter greater than 4.30 mm, all the other eigenvalue densities of macropores had a significantly positive correlation with the saturated hydraulic conductivity. Conclusion (1) In the 0−30 cm soil layer, the saturated hydraulic conductivity of most sample plots decreases with the soil depth increasing, but it possibly increases with the soil depth increasing. (2) The equivalent diameter of macropores in the soil of forest is mainly concentrated in 0.31−2.30 mm, and its occupancy rate is more than 95%. (3) When equivalent diameter of macropores is smaller, the density of characteristic parameter of macropore structure is greater except for the volume and surface area of macropores. (4) There is a significantly positive correlation between the characteristic parameter of macropores and the saturated hydraulic conductivity except for the volume density of macropores with equivalent diameter greater than 4.30 mm. The influence of macropore number on saturated hydraulic conductivity is significantly greater than structure parameters of macropores. -
图 1 大孔隙数量密度分布
d0.31、 d1.31、 d2.31、 d3.31和 d4.30分别代表孔径为0.31 ~ 1.30 mm、1.31 ~ 2.30 mm、2.31 ~ 3.30 mm、3.31 ~ 4.30 mm 和 > 4.30 mm的大孔隙。横坐标中第1个数字代表样地编号，第2个数字代表土层深度，例如：1−2，1代表样地1，2代表土层10 ~ 20 cm，以下类同。 d0.31, d1.31, d2.31, d3.31 and d4.30 represent macropores with equivalent diameter of 0.31−1.30 mm, 1.31−2.30 mm, 2.31−3.30 mm, 3.31−4.30 mm and large than 4.30 mm, respectively. The first number in the abscissa represents sample plot No., and the second number represents soil layer depth, for example, 1−2, 1 represents the sample plot 1, 2 represents the soil layer of 10−20 cm, the following is similar as this.
Figure 1. Quantity density distribution of macropores
图 8 大孔隙特征参数对饱和导水率的影响
Figure 8. Influence of characteristic parameters of macropores on saturated hydraulic conductivity
表 1 样地基本情况
Table 1. Basic situation of sample plots
样地
Sample plot经纬度
Longitude and
latitude样方大小
Sample plot
size (m × m)海拔
Altitude/m林地类型
Forest land type平均树高
Average tree
height/m郁闭度
Canopy
density/%平均胸径
Mean DBH/cm样地1 Sample plot 1 40°30′43″N，116°49′51″E 20 × 20 225 人工林 Plantation 11.91 90 22.84 样地2 Sample plot 2 40°30′27″N，116°49′14″E 20 × 20 227 人工林 Plantation 10.29 90 25.63 样地3 Sample plot 3 40°30′10″N，116°48′46″E 20 × 20 225 人工林 Plantation 12.63 85 16.58 样地4 Sample plot 4 40°30′27″N 116°49′02″E 20 × 20 219 人工林 Plantation 8.64 80 28.34 样地5 Sample plot 5 40°30′34″N，116°49′31″E 20 × 20 218 人工林 Plantation 7.54 80 16.73 样地6 Sample plot 6 40°30′50″N，116°50′16″E 20 × 20 217 人工林 Plantation 11.24 85 24.46 
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表 2 大孔隙特征参数与饱和导水率相关性检验
Table 2. Correlation test between characteristic parameters of macropores and saturated hydraulic conductivity
项目
Item饱和导水率 Saturated hydraulic conductivity d0.31 d1.31 d2.31 d3.31 d4.30 数量密度 Quantity density 0.671 (0.002**) 0.745 (0.000**) 0.773 (0.000**) 0.791 (0.000**) 0.814 (0.000**) 长度密度 Length density 0.673 (0.002**) 0.782 (0.000**) 0.799 (0.000**) 0.762 (0.000**) 0.627 (0.005**) 体积密度 Volume density 0.712 (0.001**) 0.803 (0.000**) 0.804 (0.000**) 0.775 (0.000**) 0.294 (0.237) 表面积密度 Surface area density 0.696 (0.001**) 0.772 (0.000**) 0.778 (0.000**) 0.789 (0.000**) 0.748 (0.000**) 迂曲度密度 Tortuosity density 0.663 (0.003**) 0.776 (0.000**) 0.800 (0.000**) 0.770 (0.000**) 0.765 (0.000**) 倾斜角度密度 Tilt angle density 0.659 (0.003**) 0.716 (0.001**) 0.745 (0.000**) 0.783 (0.000**) 0.802 (0.000**) 注：** 表示在 0.01 级别(双尾)相关性显著。*表示 在 0.05 级别(双尾)相关性显著。Notes: ** means the correlation is significant at 0.01 level (double tail), * means the correlation is significant at 0.05 level (double tail).
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