武汉月湖水生植被重建的实践与启示

PRACTICE AND IMPLICATION OF ESTABLISHING AQUATIC VEGETATION IN LAKE YUEHU IN WUHAN,CHINA

通过生物操纵、浮水植物和植物浮岛原位净化、岸边人工湿地净化和科学种植等措施,2—3年内,在长江中游地区、面积为0.66km2、水质为劣Ⅴ类的重富营养湖泊武汉月湖重建了以菹草和伊乐藻为优势种的沉水植物先锋群落,2005年春季的沉水植物盖度达到45%,提高了透明度。利用水位低、透明度相对高的冬季种植伊乐藻、菹草等适合冬春季生长的沉水植物是建立沉水植物先锋群落的一个有效途径。重污染水体过低的透明度是重建沉水植被的主要限制因子,在低水位或较高透明度时期,水生植物可以耐受相对较高的污染负荷,并且在有条件降低水位时,会大大提高重建沉水植被的成功率。重建并保持长期稳定的水生植被必须截污,并把营养盐浓度削减到一定范围内。水生植被重建初期是最脆弱的时期,水位、污染负荷等生态因子的较大波动很容易破坏植物群落,在这一时期要尽量保持关键因子的稳定,注意控制浮萍的扩张,使形成的生态系统逐步走向成熟。清除鱼类对提高水的透明度有重要作用,但必须伴随着水生植被的恢复或重建才能维持长久的良好效果。

Lake Yuehu locates in Wuhan city,which is in the middle reach of the Yangtze River. It is a small （0.66 km2 ） and shallow hypereutrophic lake,consists of Lake Small Yuehu and Lake Large Yuehu. The water quality of the lake was worse than Class Five （ a water quality standard of China）. Pioneer submersed plant community dominated by Potamogeton crispus and Elodea nuttallii was established within 2--3 years by the help of biomanipulation, purification of water with floating-leaved plants and plant floating islands in the lake, purification with wetland on the bank, transplantation of sub- mersed plants and so on. In the spring of 2005, the coverage of submersed vegetation was 45 %. Transparence of the water was improved markedly. It was an effective way to establish pioneer submersed plant community by transplant Potamogeton crispus and Elodea nuttallii in winter when water level was lower and its transparence was higher than other seasons of a year. In the hypereutrophic water body,low transparence was the key factor limiting to rebuild submersed vegetation. When water level was lower or transparence was higher, aquatic plants could resist pollution more. If water level could be low- ered, the effort to rebuild submersed vegetation would be more successful. To rebuild and maintain the vegetation, sewage interception was necessary, and the concentrations of nutrients in the water, such as nitrogen and phosphorous, must be reduced to some extent. The newly rebuilt plant community was the weakest. Intensive fluctuations of some major environmental factors, such as water level, pollution load and so on, could easily destroy the plant community. Therefore,in this period, it was necessary to keep these factors steady and to prevent outspreading of duckweed. It was effective to improve the water transparence by fish clear along with aquatic vegetation restoration.