Abstract: School of Geography Science, Nanjing Normal University Seven plots were laid out from sea to land along the intertidal gradient on tideland of the coast of Xinyanggang, North Jiangsu and labeled as mudflat, spartina alterniflora patch (SAP), lower edge of stable S. alterniflora flat (SAfI), S. alterniflora flat 2003 (SAF03), S. alterniflora flat 1989 (SAF89), Suaeda salsa (SS) and grass flat (GF). In each plot (1 m × 1 m in quadrat, 3 replicates), 9 S. alterniflora tiller seedlings, similar in growth for all the plots, were cultivated in situ for observation of their breeding success rate and hence study on their expansion ability in the coastal wetland of North Jiangsu. Results show that (1) The survival rate of the seedlings was 7.8% in mudflat, significantly lower than in the others except SS (P＜0.05) and was 88.9%, 77.8%, 60.0%, 81.1%, 0 and 66.6% in SAP, SAFI, SAF03, SAF89, SS and GF, respectively; (2) Number of rhizomes of the plants in mudflat was significantly higher in mudflat than in the others, but thousand grain weight (TGW) of the plants in mudflat was significant lower than in the other plots (P＜0.05); On D127 the number of the plants increased by 24.8 times in mudflat, by 19.7 times in SAP, by 30.2 times in SAFI, BY 6.7 times in SAF03, by 5.8 times in SAF89 and by 3.0 times in GF over the number of the plants that survived at the first phase; (3) SAP, SAFI and SAF89 was significantly higher in total biomass of the plants than the other plots and differed very slightly between them, displaying a trend with SAFI being the summit declining towards the land and the sea; the plants in mudflat and GF were low in spike biomass, but high in rhiomass. It was also found that S. alterniflora in the area close to the sea was rather stronger in expansion ability as affected by tide, soil moisture content, wind and waves, and the plants in mudflat were dwarf. For reproduction and expansion of the population, it is more advisable to choose asexual reproductive strategy in areas close to the sea and to the land, and a mixed strategy of sexual and asexual reproductions at the central belt of the tidal flatland.

Key words: Spartina alterniflora, reproductive strategy, expansion ability, exotic species