Seasonal Dynamics of Nitrogen and Phosphorus in Phragmites australis and Spartina alterniflora in the Wetlands of Min River Estuary

Seasonal dynamic of the nitrogen and phosphorus concentration and accumulation of Phragmites australis and Spartina alterniflora was investigated over one year in the wetlands of Min River estuary.The results showed that the concentration of nitrogen and phosphorus in aboveground fractions were highest in leaves,then was flower,the lowest was in stem,and concentration of nitrogen in the leaves of Phragmites australis was significantly higher than that in Spartina alterniflora(n=3,p0.05).Concentration of nitrogen and phosphorus in living plant was higher than that of dead one,and concentrations of nitrogen and phosphorus in spring and winter were higher than those in autumn and summer.Accumulation of nitrogen and phosphorus in aboveground fractions were highest in leaves,then was stem,the lowest was in flower,and accumulation of nitrogen and phosphorus in living leaves and stem of Spartina alterniflora were significantly higher than those in Phragmites australis(n=3,p0.05).Concentration of nitrogen and phosphorus in belowground part of Phragmites australis was highest in 0～15 cm,then in 15～30 cm,the lowest was in 30～60 cm,which was directly opposite in Spartina alterniflora.Accumulation of nitrogen and phosphorus in belowground part of two plants was highest in 0～15 cm,then in 15～30 cm,the lowest was in 30～60 cm.Accumulation of nitrogen and phosphorus in belowground of Phragmites australis was always higher than those in aboveground,which was directly opposite in Spartina alterniflora.From the N/P,it's concluded that primary productivity was nitrogen-limited.