HR: 13:40h
AN: H42H-01    [PDF]
TI: Effects of Model Resolution on Predictions of Vegetation Health in Water-Limited Ecosystems
AU: * Guswa, A J
EM: aguswa@smith.edu
AF: Picker Engineering Program, Smith College, Northampton, MA 01063 United States
AU: Celia, M A
EM: celia@princeton.edu
AF: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544 United States
AU: Rodriguez-Iturbe, I
EM: irodrigu@princeton.edu
AF: Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544 United States
AB: Water-limited ecosystems are characterized by precipitation with low annual totals and significant temporal variability, transpiration that is limited by soil-moisture availability rather than atmospheric demand, and infiltration events that may only partially rewet the vegetation root zone. Average transpiration in such environments is controlled by precipitation, and accurate predictions of vegetation health require an adequate representation of the temporal variation in the timing and intensity of plant uptake. Complexities introduced by variability in depth of infiltration, distribution of roots, and a plant's ability to compensate for spatially heterogeneous soil moisture suggest a minimum vertical resolution required for a satisfactory representation of plant behavior. To explore the effect of model resolution on predictions of vegetation health, we conduct a series of numerical experiments, comparing the results from models of varying resolution for a range of plant and climate conditions. Plant uptake is represented with a Type I model, in which flow through the soil-atmosphere-plant continuum is driven by a potential difference across a network of resistances. To isolate the effects of spatial variations in soil-moisture and uptake, infiltration is simplified to occur instantaneously in response to intermittent storms arriving as a Poisson process. From temporal and spatial scales of the underlying processes and desired output, we develop a dimensionless parameter that indicates the adequacy of a finite-resolution model with respect to reproducing characteristics of plant transpiration over multiple growing seasons. This parameter may be used to determine the spatial resolution required to predict vegetation health in water-limited ecosystems accurately.
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting