三峡坝下游沙洲植被动态对水沙情势的响应及机理

In post-Three Gorges Dam period, vegetation dynamic on downstream sand bars was accelerated accompanied by lasting area decreasing and extensively eroding of the sand bars, due to the clear water releasing. The vegetation dynamic does not only response to the flow-sediment regime and the sand bar geomorphological process, but also affect the sand bar geomorphological process conditioned by the flow-sediment regime. The knowledge of the interaction and the succession trend of the vegetation dynamic and the geomorphological process under certain flow-sediment regime, is crucial to formulate the response mechanism of the vegetation dynamic on sand bar in downstream of Three Gorges Dam to the regime of flow and sediment. However, this knowledge is still missing. To fill this gap, a typical sand bar Guanzhou was selected as the study area. Drone remote sensing, field survey, permanent quadrat, in-situ observation, laboratory experiment and multivariate analysis were adopted to conduct this study. Through this study, it was expected to monitor the dynamic of the vegetation, sand bar geomorphy and the flow-sediment regime on the sand bar, quantitative analysis the thresholds of the biogeomorphic phases, improve the knowledge of the succession trend of vegetation dynamic and the interaction of the vegetation dynamic and the geomorphological process under certain flow-sediment regime, then formulate the response mechanism of the vegetation dynamic on sand bar in downstream of Three Gorges Dam to the regime of flow and sediment. These knowledge would support the research of sand bar succession theory, the development of sand bar ecological engineering projects and the management of sand bar farming in downstream of Three Gorges Dam.

三峡水库建成后，清水下泄的水沙情势使得坝下游沙洲出现了持续的面积减小和整体蚀退，沙洲植被动态演替也随之加快。沙洲植被动态演替过程，一方面受到水沙情势和沙洲地貌过程的影响，另一方面也通过生物地貌过程在一定水沙条件下影响沙洲地貌。因此，认识沙洲植被与沙洲地貌在不同水沙干扰条件下的不同相互作用和演替趋向成因，对阐明坝下游沙洲植被响应水沙情势的机制具有重要意义。但目前仍缺乏这方面的认识。为此，以典型沙洲关洲为对象，综合应用无人机遥测、野外踏勘、固定样方、原位监测、室内实验和多元分析等方法，监测植被、地貌和水沙特征的动态变化，定量分析沙洲生物地貌演替阶段的阈值条件，研究基于生物地貌演替阶段的沙洲植被动态趋向，揭示沙洲植物群落进展演替和逆向演替过程中植被、地貌和水沙的相互影响，阐明沙洲植被动态响应水沙情势的生物地貌学机制，将为三峡坝下游沙洲发育机制研究、洲滩生态工程和洲滩农业提供数据积累和理论基础。

随着三峡大坝的建设运行，坝下游沙洲对于河道稳定、航道整治、沙洲湿地和农业生产均发挥着重要作用。在清水下泄背景下，坝下游沙洲动态及演变趋势，沙洲植被及其与沙洲地貌的相互作用，对坝下游沙洲发育机制研究、洲滩生态工程和洲滩农业具有重要意义。本项目以三峡大坝下游江心洲为研究对象，研究了坝下江心洲的植物群落物种组成与结构特征；探究了坝下江心洲群落功能性状随水淹强度的变化关系以及性状间的相关关系；研究了坝下游江心洲主要物种的叶片性状对水淹强度的响应；探讨了坝下江心洲结合植物群落的洲滩生物地貌演替特征；探究了坝下江心洲长时间序列的动态变化规律及江心洲的演变趋势；探究了江心洲动态变化对景观多样性和物种多样性的影响。研究结果揭示了坝下游江心洲动态变化及其与植物生态变化的过程机制，可为三峡坝下游沙洲发育机制研究、洲滩生态工程和洲滩农业提供数据积累和理论基础。