Estimation of soil water retention function based on asymmetry between particle- and pore-size distributions.

摘要

By examining the symmetry between the distributions of particle-size (PSD) and pore-size (POD) in a soil, as hypothesized by early pore-solid fractal (PSF) models, we found significant discrepancies in fractal dimensions between the PSD and the water retention curve (WRC) of a soil. Therefore, we developed an asymmetry-based PSF model to estimate better the WRC directly from the PSD data of a soil. To do so, we adopted the concept of a microscopic arrangement of different-sized particles to address such asymmetry, and evaluated the performance of the modified PSF model on five soil textural classes (coarse-, moderately coarse-, medium-, moderately fine- and fine-textured soils) using experimental PSD and WRC data from the UNSODA database (159 undisturbed soils for model calibration and 70 undisturbed soils for model validation). The fit of the symmetry-based PSF model to the calibration dataset showed that the fractal dimension of the WRC (D_p) was slightly larger than that of cumulative mass distribution of particles (D_s) for most soils. The asymmetry-based PSF model performed better than the symmetry-based PSF model. In addition, the asymmetry-based PSF model reduced the tendency to under estimate soil water content for a given matric head and the performance of the asymmetry-based model was consistent irrespective of soil texture, indicating that the adoption of asymmetry between the PSD and the POD was adequate in predicting the WRC of a porous, particulate system such as soil.Digital Object Identifier http://dx.doi.org/10.1111/j.1365-2389.2010.01347.x