The Research Of Plant Functional Traits In Beijing Yeyahu Wetland

Global warming affect the geological distribution and quality of wetland severely. In recent 20 years, precipitation amount decreasing and evaporation acceleration made Beijing rivers becoming discontinuous flows, which definitely lead to water area shrinked and underground water level dropped, which, in consequently, drived to emerge of large area of original water surface. In such region, wetland lost its reliable existing hydrological conditions; hydromorphic soils, which is wetland unique soil, kept on degenerating and changing in physical and chemical properties. These changes caused the re-composition of wetland plants-the acquatic and wetland plants are degeneration while xerophyte and salt tolerant plants are invading-and turning the wetland ecology system back to xeric ecology system, which is a converse process and lead to the declining and even lose of the function of wetland purifying water and degradation pollutants.This essay studied the wetland ecosystem of Yeyahu Lake, analyzing the trends of wetland soil physical and chemical properties affecting by underground water level, discussing the wetland soil various factors' influences on wetland vegetation. In order to reveal the compostition trends of wetland plants, this essay used plant functional triats methods to investigate and categorize Yeyahu Lake wetland plants according to various fuctional properties. Furthermore, this essay adopted belt transects and quadrat combined methodology, the factors we have surveyed include the depth of water table, soil humidity, pH, soil salt content, soil Nitrogen content, oxidation-reduction potential(Eh), plant species, quantity, coverag; the survey of plant functional traits include the leaf Nitrogen content, specific leaf area, leaf thickness, leaf dry matter content and leaf tissue density. Through the field work , experimental analysis and the statistical analysis , we have some results :(1) The diversity index of Yeyahu wetland : the Simpson index is 0.787, and the Shannon-Weiner index is 2.121. The main plants are the reed and Artemisia capillaris.(2) The soil humidity is effected by the underground water depth and pH , the regression model is : Humidity=178.777-0.104×depth of water table-15.196×pH; there is a significantly positive correlation between the Eh and pH , the regression model is Eh=276.304-44.445×pH ; the plant quantity is determined by the soil Nitrogen content , depth of water table and coverage ,the regression model is plant quantity =-4272.101+50899.178×soil Nitrogen content+2539.283×coverage﹢42.548×depth of water table; seed is the constructive species of the ecosystem , the average height of seed is determined by the soil humidity and the soil temperature, the regression model is the average height=317.711-13.060×soil temperature+3.109×soil humidity.(3)This paper investigate the plant functional traits of Beijing wetland for the first time , get the range of the nine kinds of functional traits , and through the correlation analysis , these traits could be clustered into three groups: the first group include the leaf thickness, the leaf fresh weight, the leaf dry weight, leaf area, leaf Nitrogen content and leaf volume; the second group include the leaf dry matter content and leaf tissue density; the third group only conclude the specific leaf area.(4) according to the difference of the functional traits , the wetland plants could be grouping into four functional strategy groups: the characteristics of first group are the thinner leaf, bigger leaf dry matter content and leaf tissue density; the second group characteristics are the smaller specific leaf area and leaf Nitrogen content, bigger leaf dry matter content; the third group characteristics are the thicker leaf, and smaller leaf dry matter content and leaf tissue density; the forth group characteristics are the smaller leaf tissue density, bigger specific leaf are and leaf Nitrogen content.