Abstract: Formerly, in the population dynamics models, it is assumed that the sex ratio is 1∶1, which is not always so in reality. The birth and death rates of different sex are different. In this paper, the population dynamics of different sex with different birth rate and death rate is studied. It suggest that the spreading process of one population is controlled by the female, and has no relation with the male.

Key words: Shrub, Fertile islands, Spatial heterogeneity, Soil resources, Land desertification, Arid and semi arid regions