黄土高原雨养区坡面土壤水力学性质空间特征及影响因素

Spatial Variability of Soil Hydraulic Properties and Influence Factors on Hillslope in Rainfed Region of the Loess Plateau

土壤水力学性质在建立水分运动模型及水土保持措施配置中具有重要作用。以网格采样测定了黄土高原雨养区坡面土壤水分特征曲线,拟合了Van Genuchten和Gardner模型参数,并利用经典统计和地统计方法分析了其空间分布特征及影响因子。结果表明:在黄土高原雨养区复杂的土地利用结构下,坡面表层土壤水力学性质具有明显的空间变异性,Van Genuchten模型参数n不存在空间相关情况,为纯随机变量,参数a,A,B,A·B和饱和导水率的空间变异受到系统变异和随机变异的共同作用。Gardner模型参数A和B值受到有机质含量的影响,饱和含水量、田间持水量和容重与参数A,A·B及有效孔隙度之间的相关性均达到极显著水平。比重与坡面土壤水力学性质之间的相关关系不显著。土地利用和地形因子对水分特征曲线的影响明显,在高吸力阶段,上坡位比下坡位土壤保持的水分多,农田的持水能力不如草地和林地。

Soil hydraulic properties are very important in establishing water movement model and soil and wa ter conservation. In this study, soil water characteristic curves of a slope were measured based on the grid sampling in rainfed region of the Loess Plateau. The parameters of Van Genuchten and G-ardner model were fitted, and their spatial distribution characteristics were analyzed with classical statistics and geostatistics method. Then we examined the influencing factors on soil hydraulic properties. The results showed that the spatial variability of soil hydraulic properties on the slope surface was significant due to the complicated land use structure in the rainfed region of the Loess Plateau. Parameter n did not have spatial correlation and was thought as the simple random variable. The spatial variability of parameters（a, A, B, A- B） and Ks was in {luenced by systematic and random variations. The organic matter contents had effect on parametersA andB in Gardner model. Parameters A, B, and effective porosity showed extremely significant correlations with sat urated water content, field capacity and bulk density. The relationships between soil specific gravity and soil hydraulic properties were not significant. Soil water characteristic curves were influenced obviously by land uses and topography. At the high suction stage, the soil in the uphill can hold more moisture than downhill. The water holding capacity of farmland was less than grassland and forestland.