HR: 1340h
AN: A13B-0108    [Abstracts]
TI: Vegetation-soil water interaction within a dynamical ecosystem model of grassland in semi-arid areas
AU: Zeng, X
EM: xdzeng@atmo.arizona.edu
AF: Department of Atmospheric Sciences, The University of Arizona, 1118 E. 4th St., P.O. Box 210081, Tucson, AZ 85721 United States
AU: * Zeng, X
EM: zeng@atmo.arizona.edu
AF: Department of Atmospheric Sciences, The University of Arizona, 1118 E. 4th St., P.O. Box 210081, Tucson, AZ 85721 United States
AB: In semi-arid areas (e.g., part of northern Eurasia), land ecosystem is primarily determined by the annual precipitation via its impact on soil moisture. Multiple equilibrium states of an ecosystem (e.g., grassland and desert) are found to coexist, and the transition from grassland to desert is often abrupt at the boundary and can occur in both spatial and temporal domains. A dynamical ecosystem model is developed to study the vegetation-soil water interaction and provide the biophysical explanation of such abrupt transitions. It considers a single vertical column of soil and one species of grass, and has three variables: living biomass, wilted biomass, and the available soil wetness. The moisture index, which is the ratio of the annual precipitation to potential evaporation, is the only external climate driving force. Both numerical results and qualitative analysis show that the land system with soil water-vegetation interaction alone can possess multiple ecosystems over arid and semi-arid regions, as observed over northern Eurasia. And these results are robust with respect to model parameters and the transformation functions. Especially, it is found that the wilted vegetation plays a very important role in shaping the transition between grassland and desert. Further details are provided in Zeng et al. (2004a,b). Reference: Zeng X. D., S. S. P. Shen, X. Zeng, and R. E. Dickinson, Multiple equilibrium states and the abrupt transitions in a dynamical system of soil water interacting with vegetation, Geophys. Res. Lett. 31, 5501, doi:10.1029/2003GL018910, 2004a Zeng X. D., X. Zeng, S. S. P. Shen, R. E. Dickinson, and Q-C Zeng, Vegetation-soil water interaction within a dynamical ecosystem model of grassland in semi-arid areas, Tellus B. (submitted), 2004b
DE: 1615 Biogeochemical processes (4805)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting