Abstract: In the dry land habitat of alkalinized meadow in Songnen Plains,the rhizomes of Phragmites communis population are distributed in different depths of one meter soil layer,which usually live for 6 years and a few for 7～9 years or even longer.Based on the investigation of their buds,a "bud flow" model of the population was established,and the method for estimating the dynamics of its bud bank storage,i.e.,adding the input rate of 1 st year age-class rhizome buds to the storage rate of other age-classes dormant buds in the bank,was put forward.The results showed that the input rate of the bud bank increased with plant growth seasons while the burgeoned output rate exhibited a decreasing trend,whereas the output rate of the dead remained at a low level on the whole.By the end of September in the early dormant period,the input rate of the bud bank was as 2.04 times as its output rate,and the dormant buds of each age-class manifested a steady burgeoned output.Quantitative analysis indicated that the burgeoned output rate of dormant buds increased by 11% each year.In another word,11% of different age-classes dormant buds would germinate and form one-year class new rhizomes.The top of one-year class new rhizomes would develop to ramets in the next year,which would transport nutrients to nearby old-age rhizomes,and thus,maintain the vitality of old-age class rhizomes.

Key words: Phragmites communis, Rhizome, Age class, Bud bank, Bud flow model, Dry land habitat, Alkalinized meadow