Community change of dominant submerged macrophyte in Lake Honghu since 1950s

通过野外调查并结合历史数据对洪湖沉水植被进行长时间序列变化研究,构建自1950s以来洪湖主要优势沉水植物群落穗状狐尾藻(Myriophyllum spicatum)、微齿眼子菜(Potamogeton maackianus)、金鱼藻(Ceratophyllum demersum)和轮叶黑藻(Hydrilla verticillata)的群落分布图并计算其面积. 结果表明:穗状狐尾藻群落面积从1950s占全湖的6%增加至1990s的65%,而后急剧下降至2010年的2%,然后又恢复至2014年的15%;微齿眼子菜群落面积从1950s的10%增至1990s的65%,然后下降至2014年的38%;金鱼藻群落面积从1980s的6%增至1990s的39%,2010年以后则稳定在25%;轮叶黑藻群落面积1950s占全湖的32%,随后急剧下降至1980s的6%,2000年以后逐步增加,至2014年为15%. 1950s1990s,穗状狐尾藻、微齿眼子菜和金鱼藻群落分布范围从周边向湖心扩展,而轮叶黑藻群落从湖中心消失;2000年以后洪湖沉水植物群落分布破碎化明显. 分析认为,1950s1990s的围垦和水文过程变化,1990s2005年的围网养殖、水生植物过度利用以及由此导致的水质恶化等,以及2006年至今开展的拆围和生态修复是导致这些变化的主要因素. 建议取缔围网,控制入湖水质,提高水体透明度,促进水生植被恢复,但同时增加水位变幅,促进植物资源合理利用,避免沼泽化重演.;Through field surveys and historical data, the distribution and coverage of the four dominant submerged macrophytes communities(Myriophyllum spicatum, Potamogeton maackianus, Ceratophyllum demersum and Hydrilla verticillata) since the 1950s were studied in the Lake Honghu, China. The results showed that: the area of M. spicatum community increased from 6% of the whole lake area in 1950s to 65% in 1990s, with a sharp decline to 2% in 2010, and then returned to 15% in 2014. The area of P. maackianus community increased from 10% in 1950s to 65% in 1990s and then dropped to 38% in 2014. The area of C. demersum community increased from 6% in 1980s to 39% in 1990s, and then stabilized at 25% in 2010 and 2014. While the area of H. verticillata community had a sharp decline from 32% in 1950s to 6% in 1980s, and then gradually increased to 15% in 2014. From 1950s to 1990s, the distribution areas of M. spicatum, P. maackianus and C. demersum communities extended from the shallow water areas to the central areas of the lake, while H. verticillata community disappeared from the center of the lake. After 2000, the community distribution showed a character of fragmentation. We believed that the reclamation and hydrological process changes from 1950s to 1990s, the water quality deterioration which resulted from enclosure culture and excessive use of aquatic plants from 1990s to 2005, and the enclosure culture demolition and ecological restoration since 2006 were the main factors which led to these dominant submerged macrophyte communities changes. In order to protect the lake, it was suggested that the managers should ban the enclosure culture, control the quality of lake inflow and increase the transparency of the water body to restore aquatic vegetation. Meanwhile,increase in water level amplitude and the rational use of plant resources has to be promoted in order to avoid lake swamping again.