Spatial Variability of Some Soil Physical Properties on Semi-Arid Cultivated Hillslopes in Hydropedological Perspective

Hydropedology bridges hydrology to pedology, and hillslope hydropedology is central in understanding soil-topography-hydropedology interrelations. Many of soil physical properties have a deterministic control on hydropedological processes. This study aimed to evaluate spatial coupling between hydropedology and some soil physical variables on a sloping landscape, which has been under rainfed wheat cultivation for over 70 years. Twenty-nine soil profiles were open and described on topslope, shoulder, backslope, footslope, and toeslope positions on hillslopes oriented in different directions. In total, 486 soil samples were taken from A, B, and C horizons at 174 sampling points and analyzed for soil properties of wilting point, organic matter content, electrical conductivity, pH, and CaCO 3 content. Saturated hydraulic conductivity ( K s ) and infiltration rate were measured in the field during the sampling. Spatial variability of soil physical properties was analyzed by semivariograms. Soil horizonation was the most important factor controlling spatial structure of soil attributes in the study area. Majority of the semivariograms were horizon-specific in shape, geostatistical range, and spatial continuity. Many of the soil properties were strongly spatially dependent in the B horizon with a far greater geostatistical range compared to those in the A and the C horizon, suggesting that processes controlling the coupling hydropedology with soil physics were more strongly spatially dependent and continues in the B horizon than either in the A or the C horizon. The results indicated complex soil physics-hydropedology spatial coupling, which vigorously mediated by soil horizonation in the study area. More research is needed to disentangle the multitude spatial interplay of hydropedology drivers of soil, hydrology, and topography across different soil and topographic settings.