Abstract: The population patterns of main communities on halomorphic meadow of Keerqin sandyland and their formations are studied with methods of variance/mean, Greig-Smith's variance analysis for nested quadrats and Hill's pattern analysis. The results show that most of the species in Aneurolepidium ehinense and Arundinella hirta communities and all species in ecotone of these two communities are appeared as aggregated distribution. Its smallest scale is 0.01m², and the biggest is 6.4×6.4m². The minimum sampling size of grid should be less than 0.05×0.05m², and the optimal sampling size is 40.96m². The small scale pattern is caused by seed dispersion and nutrient reproduction, the middie scale one is caused by extension of stolon and long rhizome,and the large scale pattern is determined by total salt content of soil and soil pH.

Key words: Population, Aggregated distribution, Poisson distribution