Characterization of Properties and Processes in Soils Across Different Scales

A ubiquitous problem in soil and hydrological sciences is the representation of processes in the presence of large soil spatial and temporal variability at a scale larger than the one in which observations and property measurements are made. This scale-transfer problem must be solved to describe effectively the coupled fluxes of heat and moisture across large land surfaces, and to establish appropriate soil parameters for use in describing the behavior of pollutant plumes at the field or basin scale. Because different processes may dominate at different spatial or temporal scales, there is increasing awareness that scale issues are at the heart of many hydrological problems.

Theories are being developed to make the transition from one domain to another. These include upscaling or aggregation from small to large scales and disaggregation (downscaling) from large to small-scale processes. These theories include both deterministic and stochastic approaches, each of which maintains soil spatial heterogeneity. Remote sensing techniques to estimate large-scale soil parameters and in situ measurement techniques to obtain point-scale soil information are being developed. Thus, analysis and data assimilation techniques such as GIS and geostatistical tools are of critical importance to integrate scale-dependent soil physical processes. Discussion across soil physics, hydrology, and other disciplines will provide insight into how to integrate our scale-dependent knowledge to build a broadly applicable understanding.