A dynamic landscape simulation model for the alkaline grasslands on Songnen Plain in northeast China

Abstract

a dynamic model was developed to simulate the variation of spatial species distribution patterns of the meadow steppe grasslands on Songnen Plain in northeast China. Simulation was performed to study the interaction between soil alkalization and vegetation development with special consideration given to spatial processes such as horizontal species migration and horizontal diffusion of soil alkali. The coverage of five species,Calamagrostis epigeios, Aneurolipidium chinense, Puccinellia tenuiflora, Aeluropus littoralis andSuaeda corniculata, and soil alkali were selected as 6 state variables. A positive feedback mechanism embedded in the model was that when the total plant coverage is large enough, the soil undergoes de-alkalization, which in turn helps improve further the plant growth condition. The de-alkalization is due to the improved soil physical properties indicated by a large amount of soil non-capillary pores coexisting with a large amount of below-group root biomass which allows alkaline solutes to leach from surface soil to underground water by means of precipitation. On the other hand, when the plant coverage is too small, soil alkalization takes place due to the deterioration of soil physical properties indicated by a small amount of plant root biomass and a large amount of capillary pores which enables evapotranspiration to bring up alkaline solutes to the surface soil. The alkalization of surface soil further hinders plant growth.