水位变化对洞庭湖沉水植被的影响机理研究

With the aggravation of disturbances (i.e., water conservancy project and human activities) in recent 50 years, the water level of Dongting Lake has a significant decreasing tendency, and directly resulted in a disappearing of many aquatic plants. Water level plays a critical role in regulating the vegetation coverage, species composition, primary production and material energy cycle of submerged macrophyte. Therefore, the study on the water level effects on submerged macrophyte can be one of the scientific basises for water level ecological regulations in lake systems. In this project, the dominant submerged macrophytes in Dongting Lake were selected as our objects to clarify the regulation mechanisms of water level on the submerged macrophytes in Dongting Lake through following works: 1) the basic vegetation characteristics with its key influencing environmental factors were investigated by field investigation and indoor environmental factors analysis; 2) to clarify the effects of water change process on the submerged macrophyte through regular monitoring in permanent sample plots. 3) to clarify the effects of interspecies relation on maintenance of communication structure of submerged macrophytes by the competition experiment in different water environment (water levels and submerged duration). Finally, the regulation mechanism of water level changes on submerged macrophyte will be clarified by integrating the above results.

近50年来水利工程等人类活动影响加剧，洞庭湖水位呈现下降的变化特征和趋势，直接导致许多水生植物种类消失。水位变化对沉水植被覆盖度、物种组成、初级生产力及内部物质能量循环起着至关重要的调节作用，因此，研究水位变化对沉水植被的影响机理是湖泊水位生态调控的科学依据之一。本项目试图以洞庭湖典型沉水植物群落为对象，通过野外调查及室内环境因子分析掌握洞庭湖的基本沉水植被特征，揭示影响沉水植物的关键基质特征；拟通过野外设置固定样地和控制实验定期监测和分析的方法，揭示水位变化过程对典型通江湖泊沉水植物的影响动态及作用机理；拟通过不同水文因子（水位高度、持续时长等）梯度下多个竞争实验的设置，揭示种间关系在沉水植被动态及群落维持中的作用机理，最后综合各项成果系统揭示水位变化对洞庭湖沉水植被的影响机理。

近50年来水利工程等人类活动影响加剧，洞庭湖水位呈现下降的变化特征和趋势，直接导致许多水生植物种类消失。水位变化对沉水植被覆盖度、物种组成、初级生产力及内部物质能量循环起着至关重要的调节作用。本项目以洞庭湖4种典型沉水植物群落为对象，通过野外调查及室内环境因子分析掌握洞庭湖的基本沉水植被特征；通过控制实验定期监测和分析的方法，揭示水位变化过程对典型通江湖泊沉水植物的影响动态及作用机理；通过不同水文因子（水位高度、持续时长等）梯度下多个竞争实验，揭示种间关系在沉水植被动态及群落维持中的作用机理。研究表明：水深可通过改变底质理化性质，间接影响沉水植物生长；不同水深对沉水植物生长影响明显，25cm极低水深明显抑制了沉水植物的株高、分枝、茎粗等生长，75和100cm的高水位有利于沉水植物的生长；水深对沉水植物的繁殖有显著影响，不同水深对沉水植物生长长度有显著影响，25cm极低水深环境不利于沉水植被繁殖；25cm水深沉水植物可溶性蛋白含量显著低于其他水深可溶性蛋白含量，过低水深会造成沉水植物细胞的氧化损伤，其他生理活性随水位增加而增强。可见，深入研究洞庭湖低水深变化的幅度和形式如何影响水生植物的生长，对预测水生植被动态和水生态系统的恢复均有指导意义。