The Effects Of The Enrichment Of N,P On Spartina Alterniflora Invasion To Coastal Wetlands In The Yellow River Delta

Spartina alterniflora originates and acts as one of the native dominant species inthe salt marshes in North America. It has high tolerance to high stress and highcapacity of dispersal. Spartina alterniflora was introduced to China for maintainingthe coastlines and ecological economy. However, because of its high adaptive anddispersal ability, and lack of limiting factors including biotic and abiotic factors, itbecomes an invasive species. And it has been resident in low mashes of coastalwetlands in the Yellow River Delta, nevertheless, as the high environmental stressessuch as high salinity, it has not spread towards high marshes. However, humanactivities around the coastal area may result in eutrophication of coastal wetlands.Therefore, we attempt to explore the effect of eutrophication on species interactionbetween Spartina alterniflora and the local species (Suaeda salsa,Phragmitesaustralis) by conducting field experiments. We manipulated different levels ofNitrogen (0g/m2/year,5g/m2/year,15g/m2/year) andP(0g/m2/year,5g/m2/year,15g/m2/year) as well as a neighbor treatment (with andwithout local species), and we also conducted these experiments with threereplications to reduce mistakes. We found that:(1) in Phragmites australis’ zone,the increasing of N can make the relationship between Spartina alterniflora andPhragmites australis vary from facilitation(RII=0.04±0.25) to competition(RII=-0.31±0.60), but the increasing of P can lead to facilitation, and the degree of thepositive interaction was initially low(RII=0.003+0.081) then becamehigh(RII=0.400±0.243) and then fell down to be low(RII=0.280±0.626).(2) forSuaeda salsa community, the enrichment of N, P can change the relationship betweentwo species from facilitation (RII=0.02±0.03; RII=0.67±0.58) to competition(RII=-0.33±1.15; RII=-0.67±0.58), but the high rate of death(66.67%;61.11%)suggested that Spartina alterniflora was limited most by environment factors inSuaeda salsa’s zone regardless of nutrition enrichments.