Abstract: By means of the field survey of plant communities and laboratory measurements of related indicators, the temporal dynamics and distribution pattern of carbon fixation by wetland plant communities in Chongming Island were investigated. The results indicated that all plant communities were generally divided into three types: Phragmites australis, Scirpus mariqueter and Spartina alterniflora. The P. australis community was distributed all over the area which had not been cultivated in Chongming Island, and the biomass of P. australis in the north coast was the lowest. The growth peak of P. australis occurred during March to May, with a carbon fixation ability of 1.02±0.12 kg·m^-2·a^-1. The dynamic of growth of P. australis community had a close relation with change of leaf N. The community of S. mariqueter was mainly distributed in the south coast. Its growth peaked during March to May, stagnated in June, and then continued, with a carbon fixation ability of (0.33±0.05) kg·m^-2·a^-1. The community of S. alterniflora was distributed from east of the north lake to the east beach, threatening the survival of the native species badly. The growth of the community of S. alterniflora continued for all growing season, but was more rapid in July to September, with a carbon fixation ability of (1.32±0.10) kg·m^-2·a^-1. The accumulation of carbon fixation in the wetland plants in Chongming Island increased quickly during April to July, and the carbon fixation ability in the south coast showed a highest carbon fixation ability of 2.5×10⁵ t·a^-1. The results implied that the plant community in Chongming Island had a strong carbon fixation ability, but with an obviously spatial-temporal change. The wetlands at the Chongming Island play an important role in carbon-fixation enhancement and emission mitigation of greenhouse gases in Shanghai.

Key words: niche characteristics, environmental interpretation, Loess Plateau hilly region, abandoned grassland