Study On Hydrophytes Planted In Dianchi Fubao Constructed Wetland

Fubao constructed wetland is one of demonstrated projects which are built along the Dianchi road in Kunming. Project completed in November 2008, the total area is 81200m2. The artificial wetland has finished after a few months, the plants and the plant landscape are flourishing. The whole hydrophytes planted in constructed wetland are object of study in the article. There are main three parts. On the base of the field investigation, choosing seven types of hydrophytes as test materials.They are Thaliade albata, Zizania caduciflora, Phragmites australis, Typha przewalskii, Pontederi acordata, Eichhornia crassipes, Nymphaea tetragona, which all grow well. One of research contents is the content of 14 kinds of mineral elementsn in he mature leaves of test hydrophytes,which are N, P, K, Ca , Mg, Si, Cu, Fe, Zi, Pb, Al, Se, Mn, Na. Another is useing AHP to evaluate comprehensively about these seven test hydrophytes from ornamental value and nutrient absorption capacity. Specifically including 5 research as follow:(1) Through the field investigation from April to November in 2009, there are 91 plant species grown in the Fubao constructed wetlands, eighty percent of which plant in water area, which belong to 49 families and82 genera. The richest families are Asteraceae, Araceae, Cyperaceae, Gramineae.(2) Between the capacity of plants absorbing nutrients and the environment is not simple relationship.There are two factors affecting metal accumulation ability of plants: the development stage of plant, interaction between the elements. The most important factors of content about mineral nutrients are plant physiological age. N, P and K in the leaves of the plant are obviously different in the three periods, because they are easy cyclic. Other metallic are not easy loop t in leaves between the three periods. Some nutrients are promotional or inhibiting with others. The most obvious is that the performance of wetland water quality in the high content of N, P inhibits the absorption of plants'Cu.(3) The 7 kinds of hydrophytes about the N and P have strong effects. The floating- leaved water Nymphaea tetragona and floating plants Eichhornia crassipes have the strongest capacity. The maximum content of Nymphaea tetragona about N is 3.94%, The maximum content of Eichhornia crassipes about P is 3.36mg/g.(4)The 7 kinds of hydrophytes have not the conformity capacity about the metallic elements and general nutrients. The highest content in plant's leaves about Fe is Nymphaea tetragona , which is 1.10mg/g. The highest content in plant's leaves about Cu and Si is Phragmites australis, which is 0.0060mg/g, 50.09mg/g. The highest content in plant's leaves about Mn and Al is Thalia dealbata, which is 0.66mg/g, 7.97mg/g. The highest content in plant's leaves about Zn, Pb and K is Eichhornia crassipes, which is 1.91mg/g, 0.0338mg/g, 23.93mg/g. The highest content in plant's leaves about Se, Ca and Mg is Typha przewalski, which is 0.0195mg/g, 7.03mg/g, 4.30mg/g. The contents in the test plants'leaves about Fe, Mn, Ca, Mg, Si, Zn are more than ordinary plants. The content about Zn is 2-5 times than normal plants, but seven kinds of plants grow well. Other elements'content of plants are within the normal range.(5) Use AHP to make a comprehensive assessment about seven hydrophytes from plant ornamental value and ecological function (the plants'absorption capacity about nutrients). There are 10 evaluation factors in the evaluation model. On the base of the field investigation and experimental results, by the way of evaluation factor weights calculation and the evaluation factors for each rate of plant, the result is: Nymphaea tetragona>Pontederia cordata > Thalia dealbata > Eichhornia crassipes > Typha przewalski >Phragmites australis>Zizania caduciflora. The advantages of Nymphaea tetragona as follow: it is a traditional ornamental water plants, the flower color of which is rich and flower in bloom has a long time. Effect of both communities or other aquatic plant decoration is most beautiful in others, while its adsorption capacity about N and P has obvious advantages. The other six plants are shown themselves advantage about elements,so don't have significant difference between the plants about comprehensive capacity. But six plants have a big difference in viewing. The flowers color and pattern of Pontederia cordata, Thalia dealbata and Eichhornia crassipes are higher ornamental than others. Phragmites australis and Zizania caduciflora are large herbaceous plant, their type slightly messy, which are suitable for planting in large water area.