Regionalization of soil water retention curves in a highly variable soilscape, II. Comparison of regionalization procedures using a pedotransfer function.

摘要

The regionalization of soil water retention curves (WRCs) with a pedotransfer function (PTF) was performed in two different ways: (i) interpolation of first the fundamental properties and applying the PTF to the interpolated data to predict the WRCs; and (ii) predicting first the WRCs by applying the PTF onto the point-wise measurements of the fundamental data, and then interpolating the WRCs. Both procedures were tested in a 1.5 km2 German soilscape (Entisols, Inceptisols, and Alfisols) with a high variability in parent material and land use. The fundamental properties were measured at the 450 nodes of a rectangular 50 X 50 m grid. The WRCs were measured at 17 irregularly distributed sites. A new PTF which had been adapted to the soilscape was used to predict the WRCs. Using procedure (i), the spatial variability of each fundamental property could be individually analysed and accounted for in the regionalization process. Thus, the root of the mean squared differences (RMSD) between the predictedand the observed water contents was 16% lower for procedure (i) than for procedure (ii). Considering the effect of land use by a residual variogram method reduced the standard deviation between predicted and observed values of organic C and bulk densityby 11 and 20%, respectively, as determined by cross-validation. The residual method produced more plausible spatial patterns of the soil water content at -300 and -15 000 hPa. As a result of the improved spatial patterns and the decrease in the regionalization error, procedure (i) was clearly superior to procedure (ii).