SPATIAL DISTRIBUTION OF NUTRIENTS OF SHALLOW LAKE IN THE ZHALONG WETLAND

1 INTRODUCTIONNitrogen and phosphorus in the water are the nu-trients limited in natural wetlands,which seriously in-fluence on the ecosystem production and the biodiver-sity(Mitsch,Grosselin,2000).Nitrogen and phos-phorus recycles have been interrupted b…

SPATIAL DISTRIBUTION OF NUTRIENTS OF SHALLOW LAKE IN THE ZHALONG WETLAND

The Zhalong wetland, a Ramsar listed wetland in China, which is located in the lower reaches of the Wuyu'er River, perennially takes in lots of nutrient input of N and P from around the catchment.Nutrient substances were especially accumulated in the shallow lakes owning to the low-lying topography.The Xianhe Lake, where is located in buffer zone of the Zhalong wetland reserve, was chosen as our target area.The spatial variation of nutrient substances in the shallow lakes was discussed and its influence factors were pointed out.The results showed that nitrogen and phosphorus in the wetland water existed mainly in the form of organic ones.The concentration of total nitrogen (TN) ranged from 0.65 mg/L to 10.64 mg/L and total phosphorus (TP) ranged from 0.013 mg/L to 0.052 mg/L.Ratio of N/P was between 25.6 and 206.5.The water quality of the Xianhe Lake has been contaminated and is in heavy eutrophication.Total P has been acting as the major limiting factor.The distribution pattern of nitrogen and phosphorus in wetland water showed characteristics of internal release except for the stream mouth area.There, the vertical distributions of nitrogen and phosphorus nutrients were from both exterior source and internal release, and was mainly influenced by exterior source during flood period.Strong hydrodynamic disturb contributed to nitrogen and phosphorus nutrients suspending and releasing in the sediments.The nutrients distribution in the water varied independent on regional changes of different frequency of hydrodynamic disturb.Mineralization and denitrification might be promoted in high frequency hydrodynamic disturb area.In growing period, the absorption of Phragmites to nutrients was an important mechanism of nutrients descending and spatial variation in the shallow lake.