汉江中下游河流湿地植被对水文情势变化的响应过程与生态机理

The Han River is the largest tributary of the Yangtze River, and the south-to-north water transfer middle route project was the great strategic project to optimize the allocation of water resources in China, to solve the problem of water shortage in the north of China. However, under the influence of a series of water conservancy projects, the hydrological regime in the middle and lower reaches of the Han River has changed dramatically, which will profoundly impact on the riverine wetland ecosystem of the middle and lower reaches of the Han River, and it is urgent to ascertain the change process and the evolution mechanism. Therefore, this project put the riverine wetlands in the middle and lower reaches of the Han River as the main research object. First, through comprehensively analysis of the effects of the south-to-north water transfer middle route project, the water diversion project from the Yangtze River to the Han River, and the cascade reservoirs projects in the middle reach of the Han River on the hydrological regimes of the middle and lower reaches of the river. Secondly, through the comparative study of the seed bank and the surface vegetation, to research the mechanism of the plant propagation dissemination and plant the diversity maintenance in the riverine wetland. Thirdly, through the research of plant vegetative growth, material distribution and reproduction strategy, to reveal the response mechanism of the plant individual to the change of hydrological regimes. The project will also research the effect of hydrological process change on plant competition, and from this, on the effect of community species composition and community structure, and based on this to explore the mechanism of plant community construction and maintenance. Finally, combination of vegetation distribution range and area variation, and through these multi-level study, the project will reveal the response process and ecological mechanism of riverine wetland vegetation to hydrological regime change in the middle and lower reaches of the Han River, and which will provide theoretical basis for the riverine wetland plant diversity conservation and ecological restoration, and put forward the countermeasures and suggestions for the ecological regulation of the dam and the management of the river.

汉江是长江最大的支流，南水北调中线工程是优化我国水资源配置、解决北方缺水问题的重大战略工程。但一系列工程建设，使汉江中下游水文情势发生了急剧变化，必将给汉江中下游河流湿地生态系统造成深刻影响，迫切需要探明其变化过程和演变机理。本项目以汉江中下游河流湿地为主要研究对象，综合分析中线调水、“引江济汉”和梯级水库等水利工程影响下汉江中下游主要水文要素的时空变化特点；通过种子库和地表植被比较研究，探讨河流湿地植物繁殖体传播和多样性维持机制；通过植物营养生长、物质分配和繁殖策略研究，揭示其个体对水文情势变化的响应机制；研究水文过程变化对植物竞争作用及由此对群落物种组成和群落结构的影响，探讨变化条件下植物群落构建和维持机制，并结合分布和面积变化，多层面揭示汉江中下游河流湿地植被对水文情势变化的响应过程与生态机理，为河流湿地植物多样性保护和生态恢复提供理论依据，为大坝生态调度和河流管理提出对策和建议。

南水北调中线工程是优化我国水资源配置、改善受水区生态环境、促进华北经济社会可持续发展的重大战略工程。也为长江大保护和汉江经济带的发展提供了重要保障。. 但工程调水量约占丹江口断面径流量的1/3，使中下游干流天然河道的流量减小、水位降低、水环境容量减少，给汉江中下游河流湿地产生深刻影响。. 为保障中下游枯水期水位，中线工程还配套实施了汉江中下游梯级渠化工程。这使得中下游天然河流变成了“河道与水库相串联”的梯级水库型河道，对汉江中下游河流湿地的水文、地貌、生态系统结构和功能乃至河流健康产生深远影响。. 依据项目任务要求，开展了：调水和梯级水利工程对汉江中下游水文情势影响、水文情势变化影响下汉江中游洲滩面积变化、基于NDVI的汉江中下游干流湿地植被时空变化及驱动力分析、典型岸带、洲滩植被对水文情势变化响应以及汉江中下游河流生态健康综合评价等研究。. 结果表明：调水和梯级电站改变了河流水文情势，在枯水期、三站整合作用下，其整体改变度可达到63.5%、下游河道的水位可下降2.5m，对下游河流湿地水环境、植被发育乃至生态健康产生深刻影响。受调水和建库影响，中游洲滩面积减少16-23%，影响了其植被的发育。淹没频率是影响干流湿地NDVI变化的主要因素（60%）。汉江中下游典型样地研究揭示了湿地植被和植物功能群沿水位高程的变化规律，得出了高程、土壤湿度、有机质及其总氮含量是影响植物梯度分布的主要因素，分析了汉江中下游主要植物群落类型和群落结构，提出了沿高程的植物群落变化规律，提出了导致植物多样性降低和植被退化的机制。运用水质、浮游动植物、植物多样性和生境特征分析了不同河段的生态健康状况及其驱动因素，提出了造流造峰的梯级水库联合调度机制以及保护水环境、减少岸带开垦和放牧以保护河流湿地健康。. 研究结果丰富了河流湿地植物生态学理论、完善了河流湿地健康评价方法，对类似河流的生态学研究和保护有借鉴意义。