A preliminary study on nonlinear vegetation-erosion dynamics model

Vegetation-erosion dynamics is a new interdisciplinary science studying the laws of evolution of watershed vegetation and erosion under the action of various ecological stresses.Based on an exponential growth model,the current linear model of vegetation-erosion dynamics can be used to simulate the vegetation growth and erosion process.However,in a period of extreme conditions,such as a period with severe soil erosion and poor vegetation cover or with high vegetation cover and low erosion,the results calculated by the model can't agree completely with the measured data.To solve this problem,a nonlinear model of vegetation-erosion dynamics based on a logistic growth model was developed in this paper.Both the linear model and the nonlinear one were applied to Xishan Area in Beijing,Huangjiaercha Watershed in Xiji County of Ningxia Hui Autonomous Region,Wangdonggou Watershed in Changwu of Shaanxi Province,and Shangyang Field Station in Huizhou,Guangdong Province,for the simulation of vegetation and erosion evolution.The results show that the two models can both accurately simulate the vegetation and erosion evolution in most periods,but in the two kinds of periods with extreme conditions previously mentioned,the simulation accuracy of the nonlinear model is much higher than that of the linear one.Nevertheless,it's much more complicated to get the solution of the nonlinear model to compare with the linear one.The nonlinear model involves two new parameters to be determined.Moreover,in comparison with the linear one,the vegetation-erosion chart derived from the nonlinear model is less realistic and is too complicated for application.More researches are needed to modify and improve the nonlinear model.