水位人为控制对湖泊沉水植被的影响及机制研究

This proposal will focus on the change of submerged vegetation caused by water level control and the triggering mechanism for the shifts between "clear-water state" and "turbid-water state" that might be the water level rising and lowering in a lake behind the theory of stable states in shallow lakes. Against the long term monitoring and observation data on the water level, transparency, aquatic plants and multi-scale investigation on the submerged vegetation and main factors of aquatic plants biotope, the difference of water level change rhythm and changes of submerged vegetation, and dominant species shifts, biotope factors before and during the water level human control will be identified by use of orthogonal transformation, spectrum analysis, multiple regression, statistical hypothesis testing. Then after, a series of experiments on the submerged plants breeding and growing are to be carried out to discover the influence of water level change and its rhythm on the growth and metabolism of dominant species and its accompanying species,competing between dominant species and its accompanying species under different water quality. On the base, a comprehensive model on submerged vegetation dynamics will be setup. The model calibration and verification will be carried out through the numerical simulation on submerged vegetation year-changes under different water regimen. Lastly, a sets of scenes of water level change according to the water level change rhythm before and during the human control will be input to the model to get the affects of water level human control on submerged vegetation and also the water level change rhythm and extreme water level which would cause the shifts between the "clear-water state" and "turbid-water state". A water level control scheme, which beneifit submerged vegetation, would be output to provide a scientific basis for Lake Taihu water level regulation decision-making.

针对湖泊人为调控改变其水位变化节律引起沉水植被的变化，以及水位抬升或降低可能是在一定营养范围内"清水态"与"浊水态"相互转化的浅水湖泊多稳态理论触发机制的问题，基于水位、透明度、水生植物长期监测与观测资料，不同时空尺度的沉水植被和其生境的观测，采用正交变换、频谱分析、多元回归与统计检验等方法，分析人为调控前后的水位变化节律，沉水植被、优势种与生境要素的变化特征；开展不同尺度的沉水植物种养与原位模拟试验，揭示不同水质条件下水位变化对优势种和伴生种生长代谢、种间竞争过程的影响及机制，创建耦合沉水植被动力学过程的综合模型，通过不同水情年沉水植被变化模拟，开展模型校验与验证；进行水位变化影响沉水植被情景设计和数值试验，分析可造成"清水态"、"浊水态"相互转化的极端水位以及水位变化节律，阐明水位人为调控对沉水植被演变的影响，提出有利于沉水植被发育扩展的水位控制方案，为水位调控决策提供科学依据。

针对湖泊人为调控改变其水位变化节律引起沉水植被的变化，以及水位抬升或降低可能是在一定营养范围内“清水态” 与“浊水态” 相互转化的浅水湖泊多稳态理论触发机制的问题，利用数理统计和小波分析开展1956-2017年太湖水位变化特征和节律分析，获得了太湖冬春年平均水位逐年升高、四季水位年变幅缩减、多年变化第一、第二显著性周期缩短等结果；研发了太湖水生植被遥感监测和湖体不同生境条件水位、水深影响沉水植物种养实验方法，提出了基于HJ-CCD数据的太湖水生植物类型遥感监测和考虑生活史的太湖沉水植物优势种遥感识别新方法，重建了1985-2017年太湖沉水植被时空分布变化过程，建立了不同生境条件下水位、水深影响沉水植物生长湖体原位保真实验方法；开展了水生植被分布区水质调查，结合1964年以来尤其是1992年以来水生植被分布区水质资料，基于CCA典范对应分析方法等，阐明了太湖水质及其营养状态长期演变过程，以及胥口湾水生植被分布区水质、底泥营养盐变化规律，弄清了太湖沉水植物优势马来眼子菜、菹草等对水体营养水平的耐受性以及叶片生理指标空间分布和太湖沉水植物分布与环境因子相关性；通过2013年至2017年太湖东部不同类型系列调查，获得了太湖水生植被尤其沉水植物空间分布、种群结构时空变化特征；开展了劣V类-II类水质水体多种特征水深、自然和人为调控水位变化对太湖沉水植物优势种、常见种植株生长及形态影响、沉水植物不同物种竞争系列实验，探讨了水位变化水深梯度对植物生长形态、生物量、竞争的影响，全面系统地获得了太湖水深及水位变化在不同水质条件下对太湖主要沉水植物光合作用、形态、生物量影响及途径，以及种间竞争受水深和水位变化影响，获得了太湖各沉水植物的生命期及其生长特点，多种沉水植物的生理、生长参数，以及生理参数随生境营养条件的变化，完善Ecotaihu模型，实现了沉水植物结构动态变化模拟，得到了太湖不同季节适应沉水植物发育的水深和水位，相关成果在太湖流域水资源和水位调度中得到了应用。