A SPATIAL SIMULATION-MODEL OF HYDROLOGY AND VEGETATION DYNAMICS IN SEMI-PERMANENT PRAIRIE WETLANDS

The objective of this study was to construct a spatial simulation mode l of the vegetation dynamics in semi-permanent prairie wetlands. A hyd rologic submodel estimated water levels based on precipitation, runoff , and potential evapotranspiration. A vegetation submodel calculated t he amount and distribution of emergent cover and open water using a ge ographic information system. The response of vegetation to water-level changes was based on seed bank composition, seedling recruitment and establishment, and plant survivorship. The model was developed and tes ted using data from the Cottonwood Lake study site in North Dakota. Da ta from semi-permanent wetland P1 were used to calibrate the model. Da ta from a second wetland, P4, were used to evaluate model performance. Simulation results were compared with actual water data from 1979 thr ough 1989. Test results showed that differences between calculated and observed water levels were within 10 cm 75% of the time. Open water o ver the past decade ranged from 0 to 7% in wetland P4 and from 0 to 8% in submodel simulations. Several model parameters including evapotran spiration and timing of seedling germination could be improved with mo re complex techniques or relatively minor adjustments. Despite these d ifferences the model adequately represented vegetation dynamics of pra irie wetlands and can be used to examine wetland response to natural o r human-induced climate change.