Variability of soil physical and hydraulic properties at the Mojave Global Change Facility,Nevada: Implications for water budget and evapotranspiration

The purposes of this study, conducted at the Mojave Global Change Facility in Nevada, USA, were to examine whether, and to what extent, spatial structure in soil physical properties would manifest as similar spatial structure in hydraulic properties and in spatial differences of evapotranspiration (ET) predictions. Soil samples were collected from 0 to 5 and 5 to 10 cm depths at each of 96 test plots. Hydraulic properties were estimated using textural properties and bulk density in the pedotransfer function method and then examined for spatial structure using variogram analysis. Results show a fining of texture at both depths in the northeast (downslope) quadrant, which led to higher water-holding capacity. Weak spatial structure was observed for most properties (ranges ～75 m). Hydraulic property data were then used as input to a one-dimensional numerical model (HYDRUS-1D) applied at each of the 96 sites for 159 days. Four different shrub cover percentages (0, 10, 20, and 30%) were used. The results showed a predominant soil evaporation-dominated water balance in the northeast quadrant of the site, regardless of plant cover. Elsewhere, plant transpiration was more dominant as percent cover decreased. Results revealed the important role that soil hydraulic properties play in near-surface water balance.