水利工程影响下河岸带和库岸带湿地植被的差异及形成机理研究

Riparian and reservoir shoreline wetlands are most common and important in regulated rivers. Although previous studies have indicated that dam construction has a negative effect on riparian and reservoir shoreline wetland ecosystems, there still remains a question about the vegetation difference between riparian and reservoir shoreline wetlands and its formation mechanism. In this project, we will investigate the standing vegetation, environmental factors (i.e., hydrology, water quality, soil characteristics,and land use) and conduct both field and greenhouse experiments in riparian and reservoir shoreline wetlands in the Han River basin. Vegetation characteristics including plant community types, species diversity, functional diversity and reproductive performance are compared between the riparian and reservoir shoreline wetlands to reveal the vegetation difference. Moreover, we will explore the relationships between dominant plant species and biotic factors (competition or facilitation) and abiotic factors (water level and soil type) to discuss the mechanism of vegetation distribution in riparian and reservoir shoreline wetlands in the Han River basin. Results from this project can provide some important information for assessing the influences of dam construction and river regulation on the wetland vegetation and for restoring the degraded vegetation in riparian and reservoir shoreline wetlands.

河岸带与库岸带湿地是筑坝河流上最常见同时也是非常重要的湿地类型，已有的国内外研究虽然已证实水利工程会对河岸带与库岸带湿地生态系统产生剧烈的影响，但到目前为止，人们对河岸带和库岸带湿地植被的差异及其形成机理还缺乏深入了解。本项目拟以水利工程较多的汉江流域的河岸带与库岸带湿地生态系统为研究对象，开展湿地植被调查与分析、环境因子（水文、水质、土壤性质和土地利用）测定、野外控制和温室控制实验。通过群落类型、物种多样性、功能多样性和繁殖策略的比较，揭示河岸带与库岸带湿地在植被特征上的差异；通过解析湿地植被与生物因素（竞争或促进）、非生物因素（水位和土壤类型）间的相互关系，阐明河岸带和库岸带植被差异的形成机理。本项目的研究结果将有助于我们全面地评价水利工程对河岸带与库岸带湿地植被的影响，并为我国河岸带与库岸带湿地生态系统的植被修复提供理论指导。

水利工程改变了河流自然的水文情势、水沙过程和地形地貌特征，并造成了河岸带和库岸带湿地植被的变化。本研究调查了汉江干流上的5个库岸带湿地和15个河岸带湿地，对比了河‒库岸带植被的物种组成和物种多样性，并探究了环境因素和植被分布的关系。我们的结果表明河岸带优势种主要为狗牙根（Cynodon dactylon）、虉草（Phalaris arundinacea）、小飞蓬（Conyza canadensis）、酸模叶蓼（Polygonum lapathifolium）和天蓝苜蓿（Medicago lupulina）；库岸带优势种为狗牙根（Cynodon dactylon）、水花生（Alternanthera Philoxeroides）、酸模叶蓼（Polygonum lapathifolium）、双穗雀稗（Paspalum paspaloides）和水蓼（Polygonum hydropiper）。库岸带的物种丰富度和多样性比河岸带低，河‒库岸带的物种相似性系数为48.5%。典型对应分析的结果表明地形因子对植物群落分布至关重要，筛选出适应地形和水热条件的湿地物种是汉江流域库岸带植被恢复的关键。本研究的结论可以为保护河‒库岸带湿地的植物多样性，以及恢复植物多样性较低的库岸带区域提供理论基础。