Monday, August 4, 2008 - 3:20 PM

OOS 2-6: Modeling of field-observed soil-plant root interactions

Jan W. Hopmans, University of California, Davis and Jirka Simunek, University of California.


Generally, there is a lack of information on soil-plant root water processes as controlled by environmental conditions near the plant-root interface. We present field experimental data that are coupled with a multi-dimensional unsaturated water flow model to better integrate scientific principles. The presented root water and nutrient uptake model links soil physical principles with plant physiological concepts, crossing disciplinary boundaries as required for advancing the science for the broad and complex study field of soil ecology. The modeling approach will greatly improve scenario testing for soil-plant systems, by including plant uptake mechanisms such as compensated root water and active root nutrient uptake. Specifically, natural ecosystems often suffer from environmental stresses (water, nutrient, temperature), and the plant responses to such limiting factors are highly relevant for understanding their functioning and survival strategies.


Field experimental results include 3-dimensional soil water content and water potential data around a single almond tree. These soil water data were coupled with a multi-dimensional soil water flow model, to infer the functional form of a 3-dimensional root water uptake model, using inverse modeling. In addition, by imposing a predetermined irrigation regime, the effect of soil water stress on tree root water uptake was determined, showing that tree roots can compensate for local water stress conditions. To improve the mechanistic description of environmental stress on root water and nutrient uptake, we present a new modeling approach that allows for inclusion of compensated root water and nutrient uptake, and provides for differentiation between passive and active nutrient uptake.