Structure and Function In Soil Hydrology

Structure of soil and soil cover is the major control of soil hydrologic functioning, being in turn controlled with multiple feedbacks. Existing methods and parameters to characterize both soil/soil cover structure and soil hydrologic functioning are scale-dependent. The purpose of this presentation is to provoke and to contribute to the discussion of “structure-function” relationships in soil hydrology by suggesting that (a) it is feasible to search for a minimum set of informative structural parameters to relate soil structure and hydrologic functioning, (b) the effect of structure on soil hydrologic function is best characterized in a stochastic rather than in the deterministic framework, and (c) the functional evaluation of structure characterization with non-invasive methods can provide useful insights. Towards the assumption (a), we demonstrate that a small number of soil and geological structural characteristics are sufficient to obtain reasonably accurate estimates of the base flow index at the watershed scale. Towards the assumption (b), we present results of statistical analysis that show relatively high probabilities of structural characteristic to be influential predictors of the saturated hydraulic conductivity at the ped/aggregate scale. Finally the assumption (c) is substantiated with the application of yield mapping data to evaluate the selection of structural units within soil cover made with the ground penetrating radar at the hillslope/field scale. Overall, relationships between soil structure and soil hydrologic functions at different scales present a promising subject of the interdisciplinary research.