水位波动节律改变后大型通江湖泊中优势水生植物体内碳氮代谢的生理响应机理研究

Water-level fluctuation is the main factor influencing the wetland ecosystem. Large hydraulic projects artificially regulate the seasonal water-level fluctuations of the river-lake floodplain system. The unnatural regulation can induce the obvious variations in both high and low water level as well as the natural fluctuations of the river-connected lakes, and then affect the growth and succession of aquatic macrophytes populations in these lakes. However, previous studies focused on their growth and survival, and there is still much need to explore the effects of the unnatural regulation activities on resource material metabolism and balance of aquatic plants. In the present study, it will be examined how the changes of water-level fluctuations affect the dominant hydrophytes (a submersed macrophyte Potamogeton malaianus and a floating-leaved macrophyte Nymphoides peltatum) with ecological importance in one of Ramsar wetland sites, the Nanjishan wetland natural reserves in Poyang Lake. This study will take the changes of hydrological regimes in Poyang Lake after the completion of the Great Three-Gorges Project as the research background, and will choose four water-depth gredients (0.5m, 1m, 1.5m and 2m) and three amplitudes of water fluctuation (0.25~0.5m per an amplitude) to quantitatively analyze the growth, morphological structure, tissue allocation, carbon & nitrogen metabolism and balance of both two species through the field investigation methods, physiological and biochemical analysis technology of aquatic macrophytes, stable isotope technology and dynamic monitoring. And it will put forth effort to reveal the effects of the constructed huge hydraulic project to carbon & nitrogen metabolism of hydrophytes in a river-connected lake and its mechanism involved, so as to provide the physiological evidence for evaluation of its cumulative ecological effect in aquatic macrophytes.

水位波动是湿地生态系统中主要干扰因子。大型水利工程改变了江湖复合系统水位季节性波动规律，造成吞吐型湖泊洪水季节淹水和枯水季节退水水位及自然节律的明显改变，从而影响湖泊水生植被的生长与演替。然而以往的大量研究集中在生长与存活方面，对物质代谢及平衡的影响机制研究仍需深入。本研究以国际重要湿地鄱阳湖南矶山自然保护区为研究区域，通过野外生态学调查方法、水生植物生理生化分析、稳定同位素技术和动态监测的手段，选取4个水位梯度处理（0.5m，1m，1.5m和2m）和3个水位波动幅度（0.25~0.5m一个幅度）来定量分析淹-退水的水文节律改变对湿地中具有重要生态功能的水生植物物种（沉水植物竹叶眼子菜和浮叶植物荇菜）在生长、形态结构、组织分配及碳氮资源代谢与平衡的影响规律，着力揭示重大水利工程运行对吞吐型湖泊水生植被的碳氮资源代谢生理影响规律及其机理，为评估三峡工程对鄱阳湖湿地植被累积性生态效应提供生理学

近年来面临着江湖关系、河湖关系和人湖关系的改变所带来的重大影响，未来鄱阳湖的发展和演变存在诸多变数和不确定性，面临着许多挑战。水位变化影响湿地水生植物群落的初级生产力、物种多样性及群落结构。鄱阳湖作为我国最大的吞吐型、季节性浅水通江湖，湖泊水位季节性变化显著。通过对丰、平、枯水期湖泊生态学调查来分析水位波动如何影响鄱阳湖优势植物群落及其响应特征。研究表明，丰水期鄱阳湖高水位导致草滩湿地植被完全淹没，潜水型湿生植物受高水位胁迫，多采取休眠或耐受的生存策略来渡过不利时期。此时期沉水和浮叶植物在湖泊占优势，优势种为竹叶眼子菜、微齿眼子菜、苦草、轮叶黑藻、金鱼藻和荇菜；枯水期鄱阳湖低水位创历史新低且提前近一个月到来，湖洲滩地的湿生植被也提前近一个月萌发，中高位草滩以中生-湿生植物类群占优势；平水期鄱阳湖洲滩部分被淹没，形成较明显水位梯度，调查表明洲滩优势湿生植物苔草属植物和虉草的地上部分生物量在水位梯度上呈显著变化的趋势。.高等水生植物具有很高的表型可塑性，在水位波动变化条件下，呈现适应对策的改变，形成具有适应大气环境而不是水环境的“生存技巧”，使得浮叶植物荇菜和沉水植物竹叶眼子菜的叶片极显著地变小，叶重变轻，叶柄变短，根变短；而总根数、总茎重极显著增大；不同组织（叶、叶柄/茎、根）间的碳氮代谢系列产物总酚、异黄酮、淀粉、FAA、SC、蔗糖、RC、FAA/SC比、FAA/TNC比等也具有显著性差异；荇菜在生态型转换后三个不同组织中总酚、异黄酮的含量呈现极显著的降低，而沉水植物的竹叶眼子菜则呈现相反的变化趋势，两指标相比均呈现显著地增加，以适应新的水-气交替的环境。.相对于非水华区，水华区的水体ρ(Chl-a)、ρ(TN)、ρ(TP)、ρ(NH3-N)明显偏高，处于富营养态；马来眼子菜叶片δ13C(0.22‰~3.91‰)、δ15N(0.66‰~10.15‰)偏低，而荇菜叶片δ13C(1.15‰~2.37‰)相对偏高、δ15N(3.02‰~4.81‰)相对偏低。水华区马来眼子菜叶与荇菜叶中δ13C、δ15N趋同，差异变小，分别为3.53‰和0.37‰(非水华区，δ13C差异为5.93‰~8.59‰，δ15N差异为0.63‰~7.50‰)；各采样点马来眼子菜叶δ15N偏高(0.37‰~7.50‰)，其δ13C变幅(3.91‰)更大(荇菜叶片为2.37‰)。