Abstract: This paper studied the temporal and spatial changes of the biomass and N content of dominant plant species at their different succession stages in Chongming Dongtan wetland. The results showed that the biomass increased gradually during growth season and reached its peak in summer, while its N content was the maximum at early growth stage and the minimum at late growth stage. During succession, the largest biomass was found at midsuccession stage. The N content in the underground part of the plants decreased with succession, while that in the aboveground part increased from mid-succession stage. The vegetation N sink in 1 hm² wetland decreased in the sequence of late succession stage>mid-succession stage>early succession stage. Among the test species, Phraqmites australis accumulated about 227.5 t N in its aboveground part, and Spartina alterniflora and Scirpus mariqueter accumulated 45.9t and 68.2t N, espectively.

Key words: Landscape change, Heihe River Basin, Landscape metrics, GIS, FRAGSTATS