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Abstract
At Tou-chian River of Hsin-chu county, the area of 1st and 2nd stages of constructed wetland is 1.9 hectare. It includes 16 different pounds from A to P. During the period of research, Sep. of 2007 to Aug. of 2008, the plants spatial heterogeneity had reach the highest percentage of 39% in Jan.2008, and the lowest of 22% in Aug. 2008. The percentage under maintenance control was between 20 to 40%. Plant species proportion in maintenance plots appears a well mix status, the species in the vegetation succession environment plots are mainly Bidens pilosa L.radiata（B1.）Sherff. The species in maintenance plots are much more divers than the vegetation succession environment plots. Plant species proportion in vegetation succession environment plots was gradually becoming even, the proportion of plant species was in an average status. From the observation of the plants’ formation of the wetlands surrounding, suppose in the undisturbed natural succession, it will eventually become a low altitude river basin vegetation structure of Taiwan. Melia azedarach L. and Trema orientalis (L.) Bl. will become the main members of this plants composition.
There are 20 family and 166 species of water plants recorded in the survey of Aug. 2008. It has 4 fmaily and 7 species more than the record of Dec. 2004 when the construction was finished. Nuphar shimadai Hayata, Bacopa monnieri（L.）Wettst. and Polygonum orientale L., these three species did not have record during the survey period. During the research period, the on land plants appeared the most in spring, total 61 family and 166 species. The least in the winter, 57 family and 149 species were recorded. However, there are 26 family, 50 genus, and 64 species more than the survey record of wetland planning in May 2004. Among the wetlands region, there are average 63% of native species in all seasons. Creating more chances for the native plants to survive by maintenance, the native plants increase 36 species in compare to the record of 2004.
Ammonia Nitrogen removed treatment was 71% in Aug.2008, had not reached the design standard. Excluding this month, all other months had exceeded the standard. It even reach 98% percent in Sept. 2007. The annual treatment average had reached 86%. However, the suspended solid (SS) treatment is not very effective, it might be caused by the lack of plants in the pond, therefore did not meet the design standard. BOD5 and NH3-N concentration in monthly average had reached the designed standard. Suspended solid (SS) concentration did not meet the standard in Sept., Oct. of 2007 and Apr., Mar., Jun. of 2008. The monthly average of water quality out concentration is above the expectation of design standard.
After the relative analysis of the plants spatial heterogeneity and NH3-N removed treatment in every pond, the reliability analysis result of the Cronbach’s α coefficient is 0.83. In pond A,H and J, the analysis result shows the changing of plant spatial coverage is highly related to the NH3-N removed treatment, and pond A had the most remarkable result. From the results of analyzing the plant diversity, pond A also had the most different and divers plants in all seasons. Therefore, we conjectured that the diversity of plants might also be close related to the NH3-N removed treatment. The P value in pond D is 0.096. However, it does not mean that the greater area of plant spatial heterogeneity is the better of NH3-N removed treatment would be.
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