HR: 0800h
AN: H31G-0736    [Abstracts]
TI: Optimality and soil water-vegetation dynamics
AU: * Schymanski, S J
EM: sschym@bgc-jena.mpg.de
AF: Max Planck Institute for Biogeochemistry, Postfach 100164, Jena, 07701, Germany
AB: Soil moisture is an important factor for nearly all hydrological and biogeochemical processes. Antecedent soil moisture impacts on infiltration and runoff generation, the soil moisture distribution within the soil together with other factors determines the soil carbon and nutrient cycling and the amount of soil moisture within the rooting zone often constitutes a major constraint for plant growth and evapo-transpiration. The main processes determining soil moisture dynamics are infiltration, percolation, evaporation and root water uptake. Therefore, modelling soil moisture dynamics requires an interdisciplinary approach that links hydrological and biological processes. Previous approaches treat either root water uptake rates or root distributions and transpiration rates as a given, and calculate the soil moisture dynamics based on the theory of flow in unsaturated media. The present study introduces a different approach to linking soil water and vegetation dynamics, based on optimality. Assuming that plants aim at minimising the costs related to the maintenance of the root system while meeting their demand for water, a model was formulated that dynamically adjusts the vertical root distribution in the soil profile to meet this objective. The model was used to compute the soil moisture dynamics in a tropical savanna over 12 months, which showed a better resemblance with the observed time series of surface soil moisture than models based on fixed root distributions. The optimality-based approach to modelling soil-vegetation interactions requires a new level of interdisciplinary synthesis, as biological and hydrological knowledge needs to be combined to derive the very basis of the model, namely the costs and benefits of different root properties. On the other hand, this approach has the potential to reduce the number of unknowns in a model (e.g. the vertical root distribution), which makes it a valuable alternative to more empirically-based approaches.
DE: 0476 Plant ecology (1851)
DE: 1813 Eco-hydrology
DE: 1851 Plant ecology (0476)
DE: 1852 Plant uptake
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2007 Fall Meeting