The succession of submerged vegetation in the northern part of Lake Fuxian and its ecological indication significance(1987-2020)

Abstract

抚仙湖有近210亿m³的优质淡水资源，具有重要战略价值，但是近年来出现水质退化的现象.沉水植被是湖泊生态系统功能维持的重要生物门类，其演变过程能反映和影响整个生态系统的变化，目前还缺乏对抚仙湖沉水植被长期连续地观测记录.本文基于Landsat遥感数据分析了抚仙湖北部沉水植被面积的动态变化，结合气候变化和水质水文要素分析发现：抚仙湖北部湖区沉水植物在1987—2020年间存在先减少后增加的变化趋势；1987—1995年，沉水植物分布面积约占北部湖区面积的1.64%；1996—2010年北部湖区沉水植被分布面积缩减，湖泊处于高水位低营养状态，水位上升是此时期沉水植物面积减少的主要原因；2011—2020年，水位降低，营养增加，营养和水位的共同作用导致抚仙湖北部湖区沉水植物面积显著增加.沉水植物覆盖度变化伴随着沉水植被以苦草为优势种群转为以穗花狐尾藻为优势种群，沉水植被结构转向耐污染性更强的属种.通过抚仙湖北部湖区沉水植被发育与营养、水位等驱动因子的关系分析，建议现阶段需要严格限制入湖氮磷排放，强化水生植被的长期动态监测，构建水量、水质、水生态一体化监测体系，并开展抚仙湖生态系统演变的模拟和预测，防止抚仙湖生态系统出现突变，以维持抚仙湖生态系统功能多样性.;Lake Fuxian has nearly 21 billion cubic meters of high-quality freshwater resources which has important strategic value, but the water quality has been degraded in recent years. Submerged vegetation is an important biological category for the function maintenance of the lake ecosystem, and its succession can reflect and influence the changes of the whole ecosystem. At present, there is a lack of long-term continuous observation records of submerged vegetation in Lake Fuxian. Based on Landsat remote sensing data, this paper analyzes the dynamic changes of submerged vegetation in the northern part of Lake Fuxian. Integrating climate change and water quality hydrological elements, submerged vegetation in the northern part of Lake Fuxian showed a decrease followed by an increase from 1987 to 2020. From 1987 to 1995, the distribution area of submerged vegetation accounted for about 1.64% of the northern lake area. From 1996 to 2010, the submerged vegetation in the northern lake area reduced, and the lake was in a state of high water level and low nutrients. The rise of the water level was the main reason for the reduction of submerged vegetation area during this period. From 2011 to 2020, the water level decreased and nutrients increased, and the combined effect of nutrients and water level led to a significant increase in the area of submerged vegetation in the northern lake area of Lake Fuxian. The change in submerged vegetation coverage was accompanied by a shift in submerged vegetation from Vallisneria natans as the dominant population to Myriophyllum spicatum as the dominant population, and the structure of submerged vegetation turns into more pollution-tolerant species. In this study, the analysis of the relationship between the development of submerged vegetation and the driving factors such as nutrients and water level in the north of Lake Fuxian suggests that at this stage, it is necessary to strictly restrict the discharge of nitrogen and phosphorus into the lake, strengthen the long-term dynamic monitoring of aquatic vegetation, build an integrated monitoring system for water quantity, quality and ecology, and carry out simulation and prediction of the Lake Fuxian ecosystem change to prevent Lake Fuxian ecosystem from regime shifts and maintain its functional diversity Lake Fuxian.