摘要:在现有众多的陆面过程模型中，对土壤水分的定量描述一般是假设垂向分布均匀，取表层土壤质地来表示整个垂向土壤质地。垂向分层和均匀处理下的土壤水分是存在差异的，这种差异有多大目前少有研究。设置3组不同饱和导水率组合的层状土壤代表不同区域的非均匀土壤，取3组层状土壤的上层土壤代表整个均匀土壤，通过建立一维土壤水分运动模型分析这种差异，同时分析饱和导水率、饱和含水量、残余含水率、孔隙大小分布参数和形状参数对层状土壤和均匀土壤的渗透量和储水量差异的敏感性，探讨垂向层状和均匀处理下土壤水分运动的差异。研究结果表明：1）建立的一维土壤水分运动模型模拟的土壤水分剖面与Yeh解析解和室内五水转化试验的土壤水分剖面一致，表明模型无论是考虑还是不考虑根系吸水都具有可靠性。2）采用垂向均匀方式处理，上下层饱和导水率相差越大的层状土壤，各水文变量的差异越大。当层状土壤上下层饱和导水率相差1.5倍时，层状土壤和均匀土壤的水分分布差别小于0.05 cm3·cm-3；而当层状土壤上下层饱和导水率相差达3.3倍时，层状土壤和均匀土壤的水分分布差别达0.15 cm3·cm-3，渗漏量相差20 cm以上，储水量相差5 cm左右。3）相对于层状土壤下层，均匀土壤下层的持水能力更差，水流速度更快，导致下层水分分布减小，渗漏量增加，储水量减小。4）形状参数n对渗透量的敏感性最强，土壤孔隙大小分布参数对储水量的敏感性最强，形状参数n其次。在实际应用中，如果一个区域的土壤上下层饱和导水率相差较大，那么垂向均匀处理可能会导致很大的误差，和实际土壤的水分分布相差很大，这会严重影响土壤水分的准确估计，在实际处理中需要认真考虑。
关键词:土壤非均匀性/
垂向均匀土壤/
土壤水分运动模型/
渗漏量/
储水量/
敏感性分析/
Yeh解析解/
室内水转化动力过程试验
Abstract:For many land surface process models, soil moisture is described quantitatively by assuming that its vertical distribution is uniform and that the upper soil texture is representative of the whole soil profile. There are differences in soil moisture between stratified and homogenous soils, which have been little documented so far in research. By setting up three stratified soil groups with different soil hydraulic conductivity combinations and using the upper soils as representative of the soil profiles of the three stratified soil groups, one-dimensional soil water movement model was established to analyze the differences in soil moisture. At the same time, the sensitivities of five parameters (including saturated hydraulic conductivity, saturated water content, residual moisture content, pore size distribution and particle shape) to the differences in leakage and water storage between stratified and homogenous soils were analyzed. It was found that:1) soil water profile simulated by the one-dimensional soil water movement model was consistent with that simulated by Yeh Analytical Solution and also that by Water Transformation Dynamical Processes Experimental Device (WATDPED) experiment. This proved that the model was reliable irrespective of whether root water uptake was considered or not. 2) The greater the difference in saturated hydraulic conductivity between upper and lower soils, the greater the difference in hydrological variables of homogeneous and stratified soils. When saturated hydraulic conductivity of the upper soil was 1.5 times that of the lower soil, the difference in soil mois-ture distribution between stratified and homogeneous soils was less than 0.05 cm3·cm-3. When it was 3.3 times, the differences in soil moisture, leakage and water storage were 0.15 cm3·cm-3, 20 cm and 5 cm, respectively. 3) Compared with the lower layer of stratified soil, water holding capacity of the lower layer of homogeneous soil was lower and with water outflow was faster, which resulted in lower moisture distribution, higher leakage and lower storage capacity in lower layer of homogeneous soil. 4) Soil particle shape (n) was the most sensitive parameter to leakage. Then pore size distribution was the most sensitive parameter to water storage, followed by soil particle shape n. In reality, if upper and lower soil saturated hydraulic conductivities differed largely, homogeneous treatment induced significant errors, differing greatly from actual soil moisture distribution in the layers. This heavily affected the accurate estimation of soil moisture, which required a realistic consideration of the use of this practice.
Key words:Soil heterogeneity/
Vertical homogeneityous soil/
Soil water movement model/
Leakage/
Soil water storage/
Sensitivity analysis/
Yeh analytical solution/
Water Transformation Dynamical Processes Experimental Device
PDF全文下载地址:
http://www.ecoagri.ac.cn/article/exportPdf?id=383277aa-c0d2-47f0-9448-ed200e7fc806
