Saturated hydraulic conductivity (K-s) is an important soil property that shows a high degree of spatial heterogeneity. There is a lack of research that investigates and determines Ks at a regional scale, due to the challenges associated with the required intensive sampling. To determine the closely correlated factors affecting K-s at a regional scale and to then generate a regional distribution map of K-s, we selected 382 sampling sites across the Loess Plateau of China (620,000 km(2)) and collected undisturbed and disturbed soil samples from two soil layers (0-5 and 20-25 cm). We found that both surface K-s and subsurface K-s had log(base 10)-normal distributions, and demonstrated strong spatial variability (CV = 206% and 135%, respectively). Surface LogK(s) was most closely correlated with LogSand, LogSilt, LogSG (slope gradient), LogSSWC (saturated soil water content), vegetation coverage and land use; while subsurface Logic was correlated with LogClay, SSWC, LogSG, LogAltitude, LogGY (growth year) and land use. Geostatistical analysis indicated that semivariograms of surface and subsurface Log K-s could be best fitted by an isotropic exponential model, with effective ranges of 204 km and 428 km, respectively. Distribution maps of K-s produced by kriging indicated a pronounced spatial pattern and demonstrated an obvious spatial depth gradient. The spatial distribution patterns of K-s at a regional scale in the loessial soils of China comprehensively reflected soil hydraulic properties and the combined effects of soil texture, vegetation, topography and human activities

Wang, YQ; Shao, MA; Liu, ZP; Horton, R. Regional-scale variation and distribution patterns of soil saturated hydraulic conductivities in surface and subsurface layers in the loessial soils of China. JOURNAL OF HYDROLOGY. 487: 13-23