Abstract: Through sampling measure on the single dominant species community in tidal-flat in Tianjin, the quantitative characteristics and the reproductive allocation on reproductive ramets of Spartina alterniflora population were studied in the ripening stage. The results showed that the w-eight of each reproductive ramet of Spartina alterniflora population was 15.62±9.26 g; the weight of ear and seeds were respectively 2.68±2.08 and 1.39±1.12 g; the number of spikelets and seeds were respectively 537.7±362.2 and 490.2±376.3; reproductive allocationⅠ(RAⅠ) and reproductive allocation Ⅱ(RAⅡ)were respectively 15.02±5.83 and 7.62±3.8%; the seed percentage was 81.9±28.6%. It is necessary to accumulate total biomass of ramet, which was more than 3.2 and 3.6 g for producing ear and seeds, respectively. There were most significant positive correlations between the length of ear and weight of ear and number of spikelets and seeds and RA Ⅰand RA Ⅱ and the height of ramet, respectively(p<0.01). There were most significant positive correlations between the weight of ear and seeds and number of spikelets and seeds and RA Ⅰand RA Ⅱ and the weight of ramet, respectively(p<0.01). There were most significant negative correlations bet-ween the number of seeds and spikelets and RAⅠand RA Ⅱand the allocation of stem and leaf sheath biomass, respectively(p<0.01).The regularities of the spatial distribution of ear are obvious.

Key words: Spartina alterniflora, reproductive module, phenotype plasticity, reproductive allocation, salt marsh