富营养湖泊夏季水生植物群落特征及其影响因素分析.doc

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摘  要

近年来由于频繁的人类活动以及管理上的疏忽，湖泊富营养化的现象越来越严重，富营养化湖泊水环境对水生植物群落的影响已成为当今重要的研究课题。本文以调研为基础，对xx市三个典型富营养湖泊（玄武湖、莫愁湖、月牙湖）的水生植物群落特征进行了分析。采用景观生态学方法，对三个湖泊选取典型样地，然后对样地内植物群落进行分类与统计，分析水生植物的种类、应用频度及盖度等数量特征，通过水生植物群落的丰富度、多样性指数以及均匀性指数3个指标来反应水生植物的群落特征。

调查结果显示，玄武湖水生植物的丰富度和多样性指数以及均匀性指数分别为7.38，6.27和1.65，是三个湖中最高的，其景观配置也较为丰富，常见植物主要为睡莲、水花生和人工栽植的荷花。莫愁湖中应用的水生植物共24种，其中荷花的应用频度最高，达90%，丰富度指数、多样性指数和均匀性指数分别为5.48，3.92和1.23，稍低于玄武湖，可见莫愁湖水生植物种类与多样性较好，但却缺乏浮水植物与沉水植物。而月牙湖中物种的丰富度指数、多样性指数和均匀度指数均为三个湖中最低，仅为3.91，3.36和1.17，可见其水生植物种类最为匮乏，植物配置也最为单调，岸边主要生长着一些水花生和五节芒、早熟禾等植物，湖面上则覆盖着大量的浮萍，浮萍使得水体透光度急剧下降，因此湖中没有沉水植物生长。总体来看，3个湖大面积应用的水生植物为水花生、黄菖蒲和早熟禾，应用频度都在30%以上，但3个湖泊的沉水植物却较为稀少，目前调查的湖泊中只有玄武湖中有金鱼藻、轮叶狐尾藻等兼具观赏价值及生态功能的沉水植物。

本文还考察了水质、水流条件、人为栽植和主导风向几个影响因素对水生植物的影响。调查结果表明，玄武湖近岸边平均水深0.48m，半数以上水域的透明度只有0.2m左右，不符合水生植物生长的条件，因此只湖北面和湖心一个岛周围这类水深较浅的区域发现了沉水植物；同时人工栽植的荷花也使得一些水域的植物群落过于单一。莫愁湖的重金属离子污染较严重，而氮、磷等营养盐方面，因管理较好的缘故各项指标均未超标，莫愁湖的平均水深约1m，水体透明度在0.4m左右，因此难以生长沉水植物。主要植物为生长在岸边的早熟禾、蛇莓等湿生植物以及人工栽植的海棠；此外，部分水面存在人工栽植的荷花与水杉，可见莫愁湖主要植物群落分布受人工栽植影响较大。月牙湖因污水的排放导致氮磷超标，使得浮萍在湖面上疯狂生长，同时因浮萍为无固定根的浮水植物，故受主导风向影响较大，主要分布在湖面下风向的一侧。月牙湖的平均水深虽然只有0.35m，但水体透明度仅0.15m左右，加上湖面上浮萍的覆盖，种种恶劣的条件使得沉水植物难以生长，因此在湖中没有观察到有沉水植物的存在。

关键词：富营养化；水生植物；影响因素；群落特征

 

ABSTRACT

Lake ecosystem is an ubiquitous ecosystem in the city in recent years. Due to human’s activities and the negligence of management, lake-eutrophication becames more and more serious in recent years. Therefore, the influence of aquatic environment on plant community has been becoming an important topic. The characters of the aquatic plants communities of three typical eutrophic lakes (Xuanwu Lake, Mochou Lake, Yueya Lake) in Nanjing was analyzed based on the survey. Using landscape ecology method, the typical sample plots were selected, and then the plant communities were classified. In order to collect the statistic data of the plant communities, the species, frequency and coverage of aquatic plant communities were analyzed. With the richness, diversity and evenness indexes, the communities’ features were reflected. 

According to the surveying results, The richness and diversity and evenness indexes for aquatic plants in Xuanwu Lake of 7.38, 6.27 and 1.65 respectively, which were higher than other two lakes. Therefore, it can be concluded that there are abundant of aquatic plants in Xuanwu Lake and the common plants are mainly water lilies, alternanthera philoxeroides and lotus. There are 24 kinds of aquatic plants in Mochou Lake, and the application frequency of lotus is highest and up to 90%, and the richness, diversity and evenness indexes were 5.48, 3.92 and 1.23, slightly lower than that of Xuanwu Lake. There is a lack of floating plants and submerged plants in Mochou Lake. The species richness, diversity and evenness indexes for Yueya Lake are of 3.91, 3.36 and 1.17 respectively, which were the lowest among these three lakes. On the bank of Yueya lake, there are some alternanthera philoxeroides, miscanthus, and early ripe grasses, etc. The lake is covered with duckweed, leading to the transparency of water dropped sharply and hence depressed growth of submerged macrophytes. Generally speaking, the application frequency of alternanthera philoxeroides, iris pseudacorus and POA accounts more than 30%, but the application of submerged macrophytes is scarce. Only in Xuanwu Lake, there are verticillatum, myriophyllum and hornwort, which have ornamental value and ecological function. 

The effects of water quality, water flow condition, artificial planting and dominant wind direction on the character of aquatic plants were also investigated. Survey results indicate that the average depth of Xuanwu Lake is 0.48m, while the transparency was only about 0.2m, which does not meet the requiretment for the growth of aquatic plants. Therefore, only in the shallow water, like the north part of the lake and the region near the island, the submerged macrophytes were found. At the same time, the artificial planting lotus blooming also makes the plant communities dull. Mochou Lake of, Due to the good management, nitrogen, phosphorus and other nutrients are not out of limits, but the pollution caused by heavy metal is serious. It is difficult for the submersed macrophytes to grow in Mochou Lake for its average depth of ~1m and water transparency of 0.4m.

The main plants on the bank of Mochou Lake are kentucky bluegrass, duchesnea indica and hygrophytes and begonia. There are artificially planted lotus and metasequoia glyptostroboides on some part of the surface of Mochou Lake, therefore, the communities are highly affected by artificial planting. Due to the discharge of sewage, the concentration of nitrogen and phosphorus in Yueya Lake are out of limits and the duckweed blooms rapidly at the same time. Because the duckweed has no stable root, the distribution of duckweed is influenced by wind direction. The average depth of Yueya Lake is 0.35 m, while the transparency was only 0.15m. Due to the coverage of duckweed, the submerged plants were not observed.

Key words: eutrophication; aquatic plants; influence factors; community characters