A Simulation Research For Invasion Speed Of Non-native Species Of Heterogeneous Environment

Using two species cellular automata model to investigate the effect of het-erogeneous landscape on invasion speed and its equilibrium density. Invasive species and native species have a competitive relationship, and invasive species has a competitive advantage. Heterogeneous landscape in the paper results from habitat loss and fragmentation. We show that:(1) Heterogeneous landscape has positive effect upon reducing invasion speed, and the effect will be enhanced with the increase of habitat fragmentation.(2) Under the same habitat destruction lev el, invasion speed will get minimum when habitat destruction manner is stochastic manner. It means that the effect of prevention will diminish or fail when the aggre-gation level of habitat destruction is strong, and the results remind us that we can not prevent biological invasions by large scale destruction with clustering manner.(3) Stochastic disturbance will reduce invasion speed of dominant species.(4) Habitat destruction is benefit to dominant species, it increases density of dominant species relatively.(5) Equilibrium density of dominant species will get maximum when habitat destruction manner is stochastic manner. Combined with previous conclusions, we know that if invasive species gets successful invasion and reach-es stable state, habitat loss will increase the final equilibrium density.(6) When the clustering degree of habitat destruction is high, the effect of heterogeneous landscape on invasion speed will tend to homogeneous landscape.(7) We take the mortality rate d as an additional means of control method (we assume biolog-ical control method cause the same damage on two species), such as herbicides, pesticides, fire. Then this control method is benefit to dominant species, not only increases equilibrium density of dominant species, but also decreases the time of the system to get stable state.