Pedometrics Research in the Vadose Zone-Review and Perspectives

Pedometrics is the application of mathematical and statistical methods for the study of the distribution and genesis of soils. Pedometrics research in the vadose zone comprises studies of the spatial and temporal dynamics of soil properties as a scientific challenge to increase our understanding of the processes at the earth's surface. While geostatistics has been the main topic of investigation, pedometrics in the vadose zone covers broader areas, which can be summarized in three main topics: (i) characterization of variability and prediction of variation of soil, (ii) sampling, measurement, and inferences of soil properties and processes, and (iii) dynamic spatiotemporal modeling. This review highlights some of the key common research areas for pedometrics in the vadose zone, showing the synergy between pedometrics and vadose zone science. A strength of pedometrics is estimating the spatial distribution of soil properties using empirical approaches. However, pedometrics needs to incorporate process-based knowledge, which adds the pedological and physical significance to the statistical robustness of predictions. A natural collaboration would therefore be with vadose zone scientists. Dynamic spatiotemporal modeling in a Bayesian hierarchical modeling framework provides a platform that will enhance collaboration between both disciplines. A future collaborative project can be envisaged to develop a global vadose zone model simulating fluxes and stores of soil water, solute, heat, and gas to address globally important issues.