Abstract: In this paper, the age structure of rhizome, vegetative productivity, quantitative relationship between potential population and actual population, and the response to soil factors of the populations of saline alkali Phragmites australis and sand P. australis were studied. In order to provide theoretical basis for the expansion of P. australis population, the mechanism of adaptation of P. australis population to soil factors was explored. The results showed that there were 6 age classes of saline alkali P. australis and sand P. australis, and 5 age classes of wet P. australis. The length of rhizome, biomass and dry matter storage of saline alkali P. australis and sand P. australis were smaller than that of wet P. australis. The age structure of rhizome length and biomass was the third age class with the largest proportion and the highest age class with the smallest proportion; the age structure of dry matter storage was the fifth age class with the largest proportion and the first age class with the smallest proportion. There was significant difference between two adversity P. australis and wet P. australis in the same age class. The pH value and salt content of saline alkali habitat were higher than those of wetland habitat, and the other nutrition indexes of saline alkali and sandy land were lower than those of wetland habitat. Soil water content and alkali hydrolyzed nitrogen content were the important positive driving factors for P. australis growth, while soil salt content was the important negative driving factor. P. australis in different habitats can cope with their own habitats by regulating the transformation between dormant buds and active buds, the development of rhizomes, and the development of main tillers and lateral tillers.

Key words: ecotype, age structure of rhizome, vegetative reproductive capacit, soil factor