Growth Characteristics, Nitrogen And Phosphorus Accumulation And Ecosystem Services Of Potamageton Crispus In Baiyangdian Lake

In recent years, the research in ecological restoration of lake aquatic ecosystem hasbecome the hot spots, and rehabilitation and restoration of the aquatic plants are focuses inthese researches. In order to control the lake’s eutrophication process, physical, chemical, andbiological methods are used and make certain effects, but the aquatic plant restoring methodwas easy to implement and had small injury on lake. Aquatic plant is the primary producer inaquatic ecsoystem and they compete for nutrition and growth space with phytoplankton andalso absorb and purify the nutrition. The aquatic plants play an important role in ecologicalrestoration of lakes. Baiyangdian Lake is located in center of Beijing, Tianjin andShijiazhuang triangle zone, belonging to Anxin, Rongcheng, Xiong, and Renqiu County. Thelake is the largest freshwater lake in North China, which functions regulation of climate,purification of water, provision of resources, and ecological restoration. But in recent years,environmental problems in Baiyangdian Lake become serious, which presenting serious soilerosion in the upstream region, lower forest, river blockage, serious sedimentation mud andshallow water scarcity, lakes water quality pollution, water eutrophication and so on. Thesituation not only influences life of the shore residents and the sustainable development ofBaiyangdian Lake, but also the natural environment of the whole North China.Potamogeton crispus is one of dominant of submersed plants in Baiyangdian Lake, itsunique life history ensures effective competition with other aquatic vegetations. This researchexplored the growth characteristics of Potamogeton crispus and the correlation with physicaland chemical methods. The direct economic value and indirect ecological value of wetlandecological services, provided by Potamogeton crispus were estimated, and the water qualitycould be improved by Potamogeton crispus, and the suitable harvest time of Potamogetoncrispus was also suggested.The results showed that the growth of Potamogeton crispus was fitted to logisticequation (Y=121.419/(1+42.814e^-0.843t))（R²=0.896，n=7）, which maximum increase rate ofbiomass was25.59g·m²·d^-1, and carrying capacity was121.419g·m^-2. There existed significant linear relations among modules of Potamogeton crispus. They developed slowly in earlyMarch and began rapid growth in early April, until mid-May they got the biggest biomass.Potamogeton crispus in Baiyangdian Lake grew abruptly from beginning of April tobeginning of May, and then decayed.Through eight-times with field data collection and determination of physical andchemical fators in the laboratory, Potamogeton crispus could adapt to environmental factorssuch as temperature, dissolved oxygen, and pH. The accumulation of nitrogen and phosphorusin each module of Potamogeton crispus varied differently, which leaf accumulation wasgreater than stem and root. The total accumulation of nitrogen and phosphorus reachedmaximum in May, which were17.76±0.20g·m^-2and1.34±0.07g·m^-2, then gradually decreasedover time. The accumulation process was closely related to the growth of Potamogetoncrispus．The total nitrogen and phosphorus in water body had a decreasing trend in early andmiddle growth phase, and the SD showed a increasing trend, indicating that Potamogetoncrispus in Baiyangdian Lake absorbed the nitrogen and phosphorus and played an importantrole in water purification. In mid-April to early May, the leaves and stems of Potamogetoncrispus absorbed nitrogen and phosphorus and released nutrients into the water from the endof May to early June, may result in increase of nitrogen and phosphorus in water.Depending on the maximum biomass of Potamogeton crispus95.88g·m^-2, carbon storagewas42.36g·m^-2. The carbon sequestration capacity of Potamogeton crispus, can be estimatedas the maximum of biomass difference accumulation in its growth period, the margin reachedmaximum64.84g·m^-2·a^-1in April, so carbon sequestration capacity of Potamogeton crispusreached28.65g·m^-2·a^-1, Further calculated the ability to release oxygen reached77.81g·m^-2·a^-1.The carbon sequestration value of Potamogeton crispus was estimated0.0075yuan per squareeach year, and the oxygen release value of Potamogeton crispus was estimated0.028yuan persquare meter each year. The nitrogen accumulation of Potamogeton crispus achievemaximum35.05g·m^-2·a^-1in early May, and Potamogeton crispus harvest can remove nitrogenelement function value about0.35yuan·m^-2·a^-1per unit area each year through the estimate ofthe domestic nitrogen content. Similarly the phosphorus accumulation of Potamogeton crispus achieve maximum8.28g·m^-2·a^-1in mid-May, similarity Potamogeton crispus harvestcan remove phosphorus element function value about0.25yuan·m^-2·a^-1per unit area each yearthrough the estimate of the domestic phosphorus content.Comparing the the ecological value created by the absorption of nitrogen and phosphorusof Potamogeton crispus, carbon fixing and potential oxygen releasing of Potamogeton crispusin different periods, the best harvest time and harvesting method were suggested for realizing,maximization of ecological service and economic benefit. The comprehensive value estimatedwas0.73yuan per meter square. By comparing the advantages and disadvantages of variousharvested, it is suggested that Potamogeton crispus can be harvested in artificial method,removing the nitrogen and phosphorus from Baiyangdian Lake.