| Dianshan lake is located in the upstream of Huangpu river, Shanghai, which is the main source of drinking water, accounts for 80% of the raw water withdrawals. Yuandang lake isoriginate from department of Dianshan lake’s bay, because of the reed beach silting, beginning into a separate lakes, at present is directly connected with Dianshan lake, has a great research significance. For the sake of revealingDianshan lake and Yuandang lake of higher aquatic plant community structure characteristics and mechanism of water quality change of time and space, to explore the water quality difference causes.In October 2013 to July 2014 for the whole area of higher aquatic plants and 29 water quality monitoring points sampling measurement and analysis of four straight quarters.Through to higher aquatic plant community investigation, determination of nutrient benchmark factor index analysis, and using Normality test, One-sample T-test, Independent-sampleT-test, Nonparametric test, Pearson correlation analysis, One-way ANOVA, Principal component analysis (PCA), Regression analysis and curve fitting method to explore the internal relation between datas, such as higher aquatic plants for main waters of Dianshan lake protection and provide a scientific basis for eutrophication control.The main results were as follows:1.There are 25 species of 18 families,18 growth forms, which approximately the same amount of 26 in 1990s. Since that year, there were 35 species of 23 families aquatic higher plants have existed in Dianshan lake, which included 17 stabled,10 disappeared, and 10 added. There were 25 higher aquatic plant association types with specific life division,4 types of emerged plants association,2 types of floating-leaved aquatic plants association,4 types of floating plants association,15 types of submerged plants association.Distribution area:autumn(58.5/km)> spring(44.64km2)> winter(28,88km2)> summer(27.33km2). Total biomass: autumn(9297.77ton)> winter(3941.61 ton)> spring(3249.71 ton)> summer(2252.03 ton). The characteristics of the general distribution are fragmental habitats and the west part of study area is more dense than the east. Aquatic plant communities vary with depth gradient distribution is irregular band and has obvious stratification.Submerged plant vertical distribution pattern both obey right skewed distribution as a whole.The mean growing point:summer> autumn> spring> winter;Partial degrees:autumn> spring> winter> summer;Kurtosis:autumn> spring> winter> summer. As to the growing point position, the vast majority of submerged plants growing point average water depth distribution in the quarter first quartile (25%), and the third quartile range (75%).According to the Lake two state theory, the result of higher aquatic plant community structure comparison indicate that the development of the two bodies of water are roughly similar. But Yuandang lake may be closer to the original point than Dianshan lake.2.The growing points of submerged plants are mainly distributed in the gap or gentle slope of the bottom. Most of the growing pointsare beyond the scope of the landscape configuration appropriate depth.The study area of higher aquatic plants along the regional growth in the direction of flow.Some aquatic plants use limited space in a specific location to form the specific optimal total association and follow certain rules:according to the root developed and flexible degree of sorting, Myriophyllumdistribution to the deepest in the center of the periphery is impacted by the water side, and as a barrier to inward for Ceratophyllum, Hydrilla verticillata, Cabomba carolinianain turn. The study found that the orientation of submerged plants from autumn to winter, which is scattered and a trend of downward.3.Nutrient reference factor in the study area of time variation characteristics: seasonal changes significantly positively related to overall and TN content had significant difference between each quarter; TP content in general no significant relationship with the seasonal change, according to the time sequence, only "spring-summer" has significant difference;Content of Chl.a general and seasonal change extremely significant positive correlation according to the time sequence, "winter spring" and "summer-autumn" has significant difference;The DO content is overall very significant negative correlation with seasonal change, all have significant difference between each quarter; SD value overall relationship with the seasonal change was not significant, only "autumn-winter" has significant difference.Annual benchmark factor importance are ranked:Autumn(TP> DO> TN> Chi.a> SD);Winter(TP> DO> TN>SD> Chl.a); Spring(Chl.a> DO>SD>TP>TN);Summer(TP> TN> DO> SD> Chl.a).To functional partition type as classification variables, each quarter of the first principal component factor respectively through the single factor analysis of variance, the results showed each quarter of the main factors in the classification of function had no significant difference in spatial distribution.Introducing revised Carlson trophic status index method (TSIM), based on main factors to each quarter nutrients nutrition state index and comprehensive evaluation of each quarter nutrition state index of the evaluation results are basically identical.Main factors to illustrate each quarter nutrients can basically represent the eutrophication status of the research region.4.The annual average level in the study area is V class water standard, Yuandang lake is slightly better in Dianshan lake. As to the quarter, the spring and autumn water quality situation slightly better, which is a class of IV, the worst is summer, which exceed V class.Spatial and temporal variations of water quality evaluation index of ashows that:according to the seasonal time series, all have significant difference;ln the spatial distribution of the functional partition had no significant difference.Each quarter of water quality in the study area generally stable, but only some partsare differences.The main reason is due to the differences in content of TP, followed by Chl.a,TN and DO. |
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