Abstract:

In recent years,because of the impact of human production activities,the nonpoint source pollution mainly from fertilizer and pesticide use and the point source pollution mainly from industrial emission were heavily increased in the whole world,especially in coastal zones.The nitrogen content increasing is a big problem we should face to.Because of the impact of the increasing nitrogen concentration,the growth of coastal vegetation has greatly changed.Spartina alterniflora is a tidal salt marsh grasses,which was the native species of the U.S.,in the east coast of the U.S.It is very important species of the terrestrial ecosystems and marine ecosystems,which could have very important influence in the inshore ecosystem water quality,hydrology dynamics and aquatic organisms.In 1979,Chinese scientist introduced this species of plant into China with a hope of making use of the benefits mentioned before.But at the same time,due to the good habitat adaptability of Spartina alterniflora,soon after the introduction,the species occupied large tracts of beach and damaged the coastal environment,especially had negative impact of the ecosystem there. Thus, in 2003,the Chinese government decided to list Spartina alterniflora as an alien invasive species in the first batch of Chinese invasion of alien invasive species lists.In this context,through the greenhouse simulation experiment,the impact of different nitrogen levels on the growth of Spartina alterniflora were studied.This research is very important because of the impact of nitrogen on invasive plants and its mechanism of action.This paper researched the impact of different nitrogen fertilizer levels in two kinds of treatments on the plant height,leaf area,biomass and other growth indicators as well as shoot ratio,root length/height and other indicators of changes of Spartina alterniflora.The results showed that with increasing nitrogen concentration,the plant height,leaf area,total biomass and aboveground biomass increased when the nitrogen level is not very high and then decreased in the high nitrogen level,while underground biomass,root to shoot ratio and root length/height ratio presented downward trend in all treatment. Various indicators in inorganic nitrogen with different nitrogen levels treatment were significantly different among all the treatments,but the difference between organic nitrogen fertilizer and inorganic nitrogen fertilizer was not significant.The result shows that an appropriate level of nitrogen supply is good for the growth of Spartina alterniflora,while the high nitrogen supply would inhibit their growth