鄱阳湖水位条件对草滩湿地优势植被的影响

Marsh wetland produced by seasonal water level fluctuations around Poyang lake has important ecological and environmental value, and is meaningful for water resource protection in the middle and lower Yangtz River.The project aimed at the Poyang Lake marsh wetland located at different elevations, the dominant species, such as Cardamine lyrata Bungein,Carex cinerascens,Phalaris arundinacea Linn. and Miscanthus saccharifleus,were cultivated using indoor experiments, with different hydrological conditions by setting different water level fluctuations. Indexes of these speciessurvival rate, rhizome diameter, leaf length, leaf area, relative growth rate, shoot height, aboveground biomass, total biomass and other indicators were subsequently measured and dealt with statistict methods. At the same time we will set the kind of typical community distribution along elevation transects in the Lake District, and survey species richness, an important value, biological diversity and evenness and other indicators within three years. Analyzing on the soil nutritional status and the surrounding hydrological station level data established on form of Lakes water level changes in DEM map will also be done. Comprehensive analysis of the impact of water level changes for the different vegetation communities using statistical methods can draw a conclusion of most suitable hydrological conditions for the protection of the general elevation of the marsh wetlands,and can provide references and help for the construction and operation of irrigation facilities around Poyang Lake.

季节性水位涨落形成的鄱阳湖草滩湿地具有重要的生态环境价值，对于长江中下游水资源保护意义重大。近年来，在气候变化和人工控湖、控河工程的影响下，长江流域部分湖泊的水位与历史相比有较大波动，湿地植被乃至整个湿地生态系统有何响应仍需要进一步研究。本项目以鄱阳湖草滩湿地分布于不同高程的优势植物种水田碎米荠、灰化苔草、荻及虉草为研究对象，采用室内培养的方法，设定不同水位波动方式，统计这些物种的存活率、根茎直径、叶片长度等若干指标对于不同水位波动方式的响应。同时在湖区设置典型群落样点以及沿高程分布的样带，在三年内跟踪调查物种丰富度、重要值、生物多样性和均匀度等指标，同时分析土壤营养状况，以周边水文站日水位数据建立湖区水位日变化DEM图，用统计学方法分析水位变化对于不同植被群落的影响。本研究一方面可以丰富现有的水位变化对湿地植被影响机理的定量研究，另一方面也可以为当地生态保护、自然保护区建设提供决策支持。

本项目从水文生态的角度，以宏观微观相结合的方式，对鄱阳湖草滩湿地优势植物进行研究。主要研究结论包括：鄱阳湖草滩的苔草和芦荻呈现出下降趋势，同期水面呈现扩大趋势；鄱阳湖区草滩湿地从高到低可分为荻、苔草、虉草、水田碎米荠、珍珠菜等优势群落；苔草分布于水淹较少，表层土含水率较低，电导相对偏高的地区，而虉草分布于淹水较多，表层土含水率较高，电导率偏低的地区。芦荻的分布则与土壤营养盐关系更大；鄱阳湖的主要优势物种分布多数与最大水深相关，其中正相关的有虉草，负相关的芦荻，苔草相关相对比较弱，表现出对水文因素的强适应性，其广阔的分布区可能是因为与虉草和荻竞争后难以占据生理最适点，而自身适应性又很好所致。苔草长势最好对应的水位波动三要素，分别是年内（秋后）出露时刻在10月下旬，年内出露时间125天左右，冬季春季各两个月总计4个月左右，最大淹没水深接近7m时。室内实验结果与野外调查结论有一定差异，水位幅度对苔草生长有显著影响，而虉草则受起始时间的影响更，差别可能源自室内模拟条件与自然条件的不同。本研究一方面可以丰富现有的水位变化对湿地植被影响机理的定量研究，另一方面也可以为当地生态保护、自然保护区建设提供参考。