长江口滨海湿地生态系统多稳态特征及形成机制研究

发布时间：2018-03-21 02:13

本文选题：滨海湿地　切入点：潮间带　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：滨海湿地生态系统作为海陆过渡带,具有净化环境、提供生物栖息地、稳定海岸、调节气候等生态服务功能。当前,在全球变化和人类活动的影响日益加剧的背景下,滨海湿地生态系统正面临着愈来愈大的压力。多稳态现象普遍存在于多种生态系统中,它与生态系统的健康和可持续发展密切相关。因此,滨海湿地生态系统多稳态研究具有重要的理论和实践意义。本研究选取崇明东滩滨海湿地生态系统作为研究区域,力图识别长江口滨海湿地生态系统中的多稳态类型,从生物地貌正反馈作用方面分析多稳态的形成机制,并在景观尺度上对该机制进行验证。主要研究结果如下:1.长江口滨海湿地生态系统多稳态类型的识别遥感影像的归一化植被指数(NDVI)分布结果显示潮间带盐沼前沿NDVI指数分布存在"双峰"特征,野外移栽实验结果表明潮间带盐沼前沿存在生物量阈值现象,均证实了长江口滨海湿地生态系统植被前沿中存在多稳态,"盐沼"和"光滩"是两种结构和功能截然不同的稳态类型。2.长江口滨海湿地生态系统中多稳态形成机制的分析长江口滨海湿地生态系统中,生物地貌正反馈作用是潮间带前沿多稳态形成的主要机制。与高程相关的淹水条件影响盐沼植物的存活、生长和繁殖状况,高强度的淹水对盐沼植物各个生活史阶段均有很强的胁迫作用,极大地限制了"盐沼"稳态的形成。密集的盐沼植被具有消浪减流作用,有利于泥沙淤积,推动了"盐沼"稳态的发展。同时,泥沙淤积与植物生物量之间存在正相关关系,泥沙淤积造成的高程抬升减少了淹水胁迫对盐沼植物的影响,进而又促进了"光滩"稳态向"盐沼"稳态的转换。这种生物地貌过程在斑块尺度上发挥作用,导致了长江口滨海湿地生态系统中多稳态现象的形成。3.景观尺度上长江口滨海湿地生态系统稳态转换的探讨景观尺度上,崇明东滩三个断面动力条件和沉积地貌呈现出明显的空间异质性。北断面潮间带盐沼前沿以潮流作用为主,水动力最弱,流向垂直于植被带,波浪强度和流速最小,水体浊度最高,水沙过程呈涨潮优势,高浊度水体高速度上滩,低浊度水体低速度下滩,这种水文动力条件极有利于细颗粒泥沙在滩面快速淤积;中断面与北断面的动力条件相似,淤积速率稍低于北断面;南断面潮间带盐沼前沿受到径流和潮流的双重作用,水动力最强,沿岸流特征较明显,波浪强度和流速最大,水体浊度极低,水沙过程涨潮优势不明显,这种水文动力条件不利于细颗粒泥沙淤积,以致于形成低淤积率的粉砂质潮滩。在景观尺度上,尽管三个断面地貌特征不同,但是在潮间带前沿均发生了"盐沼"和"光滩"之间的稳态转换。长时间尺度上的稳态转换分析表明,崇明东滩一直都存在"盐沼"和"光滩"两种稳态,但2009-2015年间"光滩"稳态向"盐沼"稳态的转换量(12.25 km2)显著高于2003-2009年(10.16 km2),"盐沼"稳态向"光滩"稳态的转换量(0.75 km2)明显低于2003-2009年(2.22 kin2)这种稳态转换现象与2003年以后河口输沙量迅速下降,2009年以后河口输沙量又趋于稳定的泥沙输入量变化息息相关。本文中生物地貌正反馈机制以及"阈值效应"等研究结果不仅可以从理论和方法上丰富滨海湿地生态系统多稳态的机理研究,也可为我国河口型滨海湿地生态系统的植被修复及综合管理提供数据支持和科学依据。
[Abstract]:The coastal wetland ecosystem as a transitional zone, with cleaning up the environment, provide habitat, stable coast, climate regulation and other ecosystem services. At present, impact on the global change and human activities in the background of growing coastal wetland ecosystem is facing more and more pressure. Multiple steady state exists in various ecosystems in the system, and it is closely related to the health of the ecosystem and sustainable development. Therefore, it has important theoretical and practical significance to study multi stable coastal wetland ecosystem. This study selected Chongming Dongtan coastal wetland ecosystem as the study area, trying to steady state type identification of Yangtze Estuary coastal wetland ecological system, the formation mechanism of the many state from the biogeomorphic positive feedback function, and verify the mechanism at the landscape scale. The main results are as follows: 1. the Yangtze River Estuary coastal Recognition of remote sensing image normalized vegetation of wetland ecosystem types in the steady state index (NDVI) results showed that the distribution of the intertidal salt marshes in front of the existence of the Shuangfeng NDVI index distribution characteristics, field transplanting experiment results show that the intertidal salt marshes are the frontier biomass threshold phenomenon, confirmed the existence of multiple steady state vegetation in the Changjiang Estuary Wetland Ecosystem frontier in the "salt" and "light tan" is a coastal wetland ecosystem in the Changjiang Estuary forming mechanism of the steady state of type.2. two structurally and functionally distinct Yangtze Estuary coastal wetland ecosystem in the steady state, biogeomorphologic positive feedback effect is the main mechanism with multi stable formation frontier intertidal. Flooding conditions correlated with elevation the influence of salt marsh plant survival, growth and reproduction of stress of high strength strong flooding on salt marsh plant has various life history stages, greatly limiting" Salt marsh "steady state. The formation of dense salt marsh vegetation has wave flow reducing effect, conducive to the sedimentation, promote the steady development of" salt ". At the same time, there is a positive correlation between plant biomass and deposition of sediment, sedimentation elevation uplift resulted in reduced water stress effects on salt marsh plants, and to promote the" light tan "to" steady state "conversion of salt marsh homeostasis. Play a role in the process of biological landscape patch scale, caused the coastal wetland ecosystem in the Changjiang Estuary multistability of.3. formation on landscape scale of Yangtze Estuary on landscape steady-state conversion of the wetland ecosystem scale, Chongming Dongtan three section dynamic conditions and sedimentary geomorphology shows obvious spatial heterogeneity. The tide dominated salt marsh intertidal frontier north section, the hydrodynamic flow perpendicular to the weakest, vegetation belt, wave intensity and minimum flow rate, water The highest body turbidity, water and sediment in the flood of high turbidity water, high speed and low turbidity water beach, low speed under the hydrodynamic condition of the beach, very beneficial for fine sediment deposition in the fast flat; similar dynamic conditions and the northern section of the interrupt, deposition rate is slightly lower than that of the north section of the dual role of the southern section; intertidal salt marsh front by runoff and tide, water power was the strongest, the coastal current characteristics is obvious, the wave intensity and the maximum flow rate, water turbidity is low, water and sediment the advantage is not obvious, the hydrodynamic condition is not conducive to the sedimentation of fine particles, resulting in the formation of low sedimentation rate in silty tidal flat. On the landscape scale, while the three section features are different, but with the steady state of frontier in the intertidal were "salt" and "light tan" conversion. The steady state on a long time scale transformation analysis shows that, Chongming Dongtan has always been there "Salt" and "light tan" two steady, but 2009-2015 years of "light Beach" to "steady state conversion of salt marsh" volume (12.25 km2) was significantly higher than that in 2003-2009 years (10.16 km2), the "steady state" to convert the light salt "beach" steady volume (0.75 km2) was significantly lower than that in 2003-2009 years (2.22 kin2) the steady-state conversion phenomenon and estuarine sediment after 2003 decreased rapidly after 2009, estuarine sediment and sediment input change tends to stable. This study is closely related to research on the mechanism of biogeomorphologic positive feedback mechanism and "threshold effect" results can not only enrich the multi stable coastal wetland ecological system from theory and method. Also, it can provide data support and scientific basis for coastal wetland ecosystem in China estuarine vegetation restoration and comprehensive management.

【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X171.1

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