Vegetative Dispersal And Relative Competitive Ability Of Spartina Alterniflora In Eastern End Of Chongming Island

Spartina alterniflora originates in east coast of North America, and acts as the native dominant species in the salt marshes. Because of its high tolerance to environment and high capacity of dispersal, S. alterniflora was introduced to China in 1979 tu accelerate the sedimentation. It has played some roles in maintaining the coastlines, but in recent years, S. altemiflora has been found to be harmful to the intertidal ecosystems in southern provinces of China because of its high invasive ability. Since the middle of 1990's, S. altemiflora was introduced several times to the Eastern End of Chongming Island, and now it is one of the greatest threats to the local wetland ecosystem. Dispersal monitoring and field competition experiments were employed to understand the vegetative dispersal rate of S. altemiflora and its relative competition ability with native species, and to propose suggestions for its control.1. I found that S. altemiflora expanded quickly in Eastern End of Chongming Island. Till 2004, it had covered an area of 540 hm2. S. altemiflora in Eastern End of Chongming Island had a strong vegetative dispersal ability. After 9 months' growth, individual S. altemiflora could develop 86-222 ramets per genet, the largest dispersal distance was 226cm. Average dispersal distance of the patches was 107cm and the largest was 263 cm.2. A non-destructive estimation of above-ground biomass had been developed in Eastern End of Chongming Island. The above-ground biomass of S. altemiflora decreased from 2073.6±682.9g/m~2 in the north subregion of Eastern End of Chongming Island to 1262.1±515.4g/m~2 in the south subregion, as the salinity decreased. The average biomass per m2 of S. altemiflora is about 2.6 times of that of Phragmites australis and 10 times of Scirpus mariqueter. The total above-ground biomass of S. altemiflora was comparable to that of Phragmites australis, and was almost 2 times of S. altemiflora. Distribution area and above-ground biomass indicated that S. altemiflora is spreading quickly in Eastern End of Chongming Island.3. Field competitive experiments and reciprocal transplant experiment show that, since the second growing season, S. altemiflora is better competitor than Scirpus mariqueter and Phragmites australis. When experiment duration increase, the intraspecific competition among the individuals of S. altenriflora will be stronger than interspecific competition. Results indicate...