HR: 0800h
AN: H51A-1115    [Abstracts]
TI: On the dynamics of soil moisture vegetation and erosion: Implications of stochastic climate forcing
AU: * Istanbulluoglu, E
EM: erkan@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Bras, R L
EM: rlbras@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Flores, A N
EM: lejo@mit.edu
AF: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AB: Landscapes are observable manifestations of dynamic interactions between climatic, hydrologic, geomorphic, and ecosystem processes. As such, understanding landscape system response to fluctuations and changes in climatic forcing is necessary to predict impacts of future climate change on landscapes, and interpret geological records as indicators of past climate. We develop a simple stochastic model for climate, soil moisture, vegetation and runoff erosion dynamics driven by the Poisson pulse rainfall model. In the model, runoff generation, moisture losses due to drainage and evapotranspiration, and vegetation growth and mortality are related to vegetation cover and soil moisture state. We apply this model to investigate the sensitivity of soil moisture, grass cover and erosion potential to rainfall variability (Rvar) and mean annual precipitation (MAP). In general, under fixed MAP and rainfall rate, both soil moisture and grass cover increase, reach a maximum, and then decrease as Rvar increases. Erosion potential tends to increase with reduced vegetation cover. Analysis of existing data suggests power-law dependence between both Rvar and interstorm period with MAP. When climate is characterized in this manner, the model shows both long-term mean soil moisture and vegetation cover increase with increasing MAP. Erosion potential, however, initially increases with increasing MAP, but reaches a peak and subsequently decreases as MAP grows large. Similar behavior between measured sediment yields and MAP have been reported in the literature for a range of climatic conditions. We find that the degree of nonlinear dependence between Rvar and MAP exerts an important control on the shape of the relationship between erosion potential and MAP. Results underscore the importance of coupled soil, vegetation and climate dynamics on erosion rates.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1851 Plant ecology
DE: 1866 Soil moisture
DE: 1869 Stochastic processes
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting