Distribution Pattern of Main Plant Populations around Tidal Creeks in Different Grades in the Jiuduansha Shoals in the Mouth of Yangtze River

In Upper shoal, Lower shoal of Shanghai Jiuduansha National Nature Reserve, according to sediment formation time and different grades of tidal creek, 17 line transects with length from 54 m to 306 m were located in the maturity tidal creeks. On each line transect, successive plots of each with an area of 150 cm× 150 cm were sampled to record the coverage of each plant species starting from the low tidal beach at the direction perpendicular to the tidal creek, based on the obtained data, the trends of plant coverage was analyzed, the distribution pattern of the main plants was also studied applying the method of the two-term local variance analysis, thus the plant distribution pattern under tidal creeks fine features was intuitively showed. The results showed that ①there were 2 vegetation subtypes, herbal marsh and salt meadow vegetation, of which herbal marshes had Scirpus mariqueter and Phragmites australis, 2 formations, and salt meadow had Phragmites australis and salt-tolerant species including Suaeda glauca and Tripolium vulgare, the invasion of Spartina alterniflora formed artificial vegetations; ②with the formation of sediments, Scirpus mariqueter and Scirpus triqueter appeared first, then Phragmites australis and other marsh plants, as hydraulic and vegetation interactive, tidal creeks are getting maturity, marsh vegetation gradually successes to salt meadow with the dominant species Phragmites australis, together with other salt-tolerant species such as Suaeda glauca, and Tripolium vulgare; ③ some local sites invaded by Solidago canadensis, Conyza canadensia, Aster subulatus and other alien plants; ④ Spartina alterniflora has been widely distributed in the survey area, across 2 vegetation subyptes ( from marsh to salt meadow vegetation), showing its broad ecological adaptability to salt and ventilation.