在重大人类活动与气候变化的双重驱动下，黄河三角洲湿地的水文连通格局不断发生变化，干扰了湿地的自然生态过程和动态平衡。潮沟网络是三角洲湿地上普遍存在的地貌景观，它调节着河口与潮间带之间水、泥沙、营养物质的交换，是三角洲湿地水文连通的主要纽带。本研究从潮沟网络入手，分析了近30多年来黄河三角洲湿地潮沟网络的时空演变规律及其关键驱动因素；以及以潮沟网络为路径的三角洲湿地纵向水文连通变化、潮沟-潮滩系统的侧向水文连通变化；识别出三角洲湿地水文连通的受损区域与稳定区域；并进一步分析了受损区域与稳定区域中潮沟网络的功能连通变化及其稳定性原理；然后从盐沼湿地生物入手，基于野外采样数据与文献调研，揭示了水文连通受损对浮游生物群落以及大型底栖动物的影响，最后提出受损水文连通的优化模式并对受损水文连通区域进行优化模拟。取得的主要结论如下：
（1）明确黄河三角洲湿地潮沟网络形态变化规律及其关键驱动因素
选取潮沟数量、级数、长度、分形维数、排水密度和排水效率等特征指标来表征潮沟网络在三角洲尺度上和分区尺度（3个子区域，分别为侵蚀区、油田区和淤积区）上的形态演变。研究表明：潮沟网络形态特征变化随着研究尺度的不同而不同。三角洲尺度上，潮沟网络呈现出简单化的发育模式。分区尺度上，侵蚀区与油田区的潮沟网络呈现出简单化的发育模式，而淤积区的潮沟网络呈现出复杂化的发育模式。潮沟网络形态变化的主要驱动因素有潮滩的侵蚀（淤积）与人类的围垦活动。分析其驱动因素可知，在三角洲尺度上，人类的围垦开发是影响潮沟网络形态发生变化的主要驱动因子；而在分区尺度上，围垦开发是侵蚀区和油田区潮沟网络形态变化的主要驱动因素，而潮滩的淤积是淤积区潮沟网络形态变化的主要驱动因素。
（2）构建纵向水文连通指数，辨识了三角洲湿地潮沟网络的纵向水文连通变化规律，识别出三角洲湿地纵向水文连通受损区域与稳定区域
研究表明：纵向水文连通指数随时间呈现出先增大后减小的趋势。截止到2018年，其综合水文连通程度在三角洲尺度上相比历史最高水平减少了85%，侵蚀区则减少将近2倍。淤积区则减少40%。从空间上看，对三角洲湿地纵向水文连通变化有重要影响的关键节点和关键边分布在侵蚀区和淤积区内的几条大型的潮沟中，油田区潮沟对整个三角洲的连通程度影响不大。从时间上看，侵蚀区潮沟网络对整个三角洲水文连通程度的影响有弱化的趋势，截止到2018年，侵蚀区内对水文连通有重要影响的关键节点和关键边几乎消失。说明该区域的纵向水文连通存在严重受损，为黄河三角洲水文连通的受损区。而淤积区的关键节点和关键边在研究时段内则保持相对的稳定状态，说明该区域的水文连通保持稳定，为水文连通稳定区。从驱动上分析，围垦开发是影响三角洲尺度上综合水文连通程度的主要驱动因素，但初期的围垦并不会影响其综合水文连通程度，只有当围垦开发比例超过40%后，围垦开发比例的进一步增大会显著降低潮沟网络的纵向水文连通程度。
（3）构建三角洲湿地潮沟-潮滩侧向水文连通指数，探索三角洲湿地侧向水文连通的变化模式
研究表明：黄河三角洲湿地潮沟-潮滩的侧向水文连通程度整体不高，且不同的区域，其侧向连通潜力不同。越靠近潮沟，其连通性潜力越高。通过分析潮沟-潮滩侧向水文连通指数得出，在三角洲尺度上，侧向水文连通程度随时间变化差异不大。而在分区尺度上，侵蚀区的侧向水文连通呈现增大的趋势，淤积区则呈现出减小的趋势，油田区在整体上变化差异不明显。进一步对其连通模式进行分类后得出，在三角洲尺度上，潮沟-潮滩的侧向总连通响应面积随时间变化而减小。其中，高连通区域面积保持稳定而低连通区域面积随时间减少。在分区尺度上，侵蚀区和油田区的总连通响应面积随时间变化减小，受损显著；而淤积区的侧向总连通响应面积随时间基本保持稳定。之后对潮沟-潮滩的侧向水文连通模式进行热点分析和趋势分析得出，潮沟-潮滩的侧向水文连通在时空上并没有形成一个连续的连通模式。“振荡”模式是整个黄河三角洲湿地侧向水文连通的主导模式。
（4）构建潮沟网络功能连通评估模型，量化不同结构连通变化下功能连通的变化规律，提出潮沟网络水文连通的稳定性原理
选取水文连通受损区和稳定区的潮沟网络进行研究。研究得出：潮沟网络水文结构连通的减小会引起其功能连通的增大。具体表现为，潮沟网络水文结构连通受损，其子网内的功能连通则会增大，子网间的流量共享程度则会减小，且子网间流量在选择传输路径中的不确定性增大。潮沟网络的结构连通变化与其功能连通变化间存在时间滞后性，即结构连通减小，并不会立即引起其功能连通的增大。作为对照，结构连通保持稳定的潮沟网络，其子网内流量的连通、子网间流量的共享以及子网间流量传输过程中信息的共享、不确定性方面均表现出稳定趋势。通过负熵理论，本研究探讨了潮沟网络水文功能连通的稳定性原理。研究得出，潮沟网络的结构连通控制着潮沟网络的功能连通，并进一步控制着潮沟网络功能连通的稳定性。具体表现为，水文连通受损的潮沟，其稳定性下降，当其结构连通受损到一定程度后，其稳定性会进一步下降并进入不稳定状态。而结构连通保持稳定的潮沟，其稳定性保持稳定。潮沟网络的结构连通单元数量控制着潮沟网络的功能连通，是其水文连通稳定性的关键指示因子。
（5）分析了纵向水文连通变化和侧向水文连通变化对盐沼湿地浮游生物群落和大型底栖生物的影响，明确水文连通受损对生物群落的生态影响
潮沟网络纵向水文连通不同，潮沟内浮游生物群落的特征也存在差异。潮沟网络纵向水文结构连通的受损不会引起浮游生物群落多样性发生显著变化，群落间的同步性变化也不显著，但会显著降低浮游生物群落的密度。所以纵向水文连通的稳定有助于提高浮游生物群落密度。对大型底栖动物的研究表明，黄河三角洲潮间带大型底栖动物群落的优势种随着研究区域的不同而不同，且具有时空差异性。相比于淤积区，侵蚀区域的大型底栖动物密度和生物量均较高，但侵蚀区域的生物多样性呈现减小的趋势，而淤积区的生物多样性基本保持稳定。侧向水文连通的受损对大型底栖动物的密度和生物量影响较小，但会显著降低大型底栖动物的生物多样性。
（6）提出受损水文连通的优化模式，并对其进行优化模拟
整合前边的研究成果，水文连通受损导致潮滩大型底栖动物生物多样性的减少，水文连通的稳定有助于提高生物多样性以及潮沟网络水文连通稳定性与其结构单元的关系，通过增加潮沟网络出口点来优化受损的纵向水文连通与侧向水文连通，使得水文连通达到稳定而提高大型底栖动物的生物多样性。结合潮沟网络现状以及其稳定所需的结构单元数量，设置7个情景进行优化模拟。研究得出，随着潮沟网络出口点的增加，其节点和边的数量也在同步增加，关键节点和关键边的数量也呈现增加的状态。随着出口点的增加，其结构连通程度呈线性增强趋势。而潮沟网络的功能连通与出口点数量的关系因功能连通指标不同而不同。出口点数量与其水文连通的稳定性同样存在显著的正相关关系，随着出口点的增加，其稳定性逐步增强。因此，潮沟网络出口点数量的优化可以促进纵向水文结构连通程度的增加，同时可以减弱其功能连通强度，而且纵向水文连通优化的同时，其侧向水文连通也得到优化。

Driven by human activities and climate change, the hydrological connectivity pattern of the wetland in the Yellow River Delta (YRD) has changed constantly, which interferes the natural ecological process and dynamic balance of the wetland. Tidal channel network is a common geomorphic landscape in delta, which regulates the exchange of water, sediment and nutrients between estuary and intertidal zone, and is the main link of hydrological connectivity of delta. In this study, the spatial-temporal evolution of tidal channel network and its key driving factors in the YRD were analyzed. The longitudinal hydrological connectivity and the lateral hydrological connectivity were analyzed. The damaged area and stable area of hydrological connectivity were identified. Furthermore, the functional connectivity variation and stability principle of tidal channel network in damaged area and stable area are analyzed respectively. Then, based on field sampling data and literature research, the impacts of damaged hydrological connectivity on plankton community and macrobenthos were revealed. Finally, the optimization model of damaged hydrological connectivity was proposed and the optimization simulation of damaged hydrological connectivity area was carried out. The main conclusions are as follows:
(1) To clarify the morphological changes and key driving factors of tidal channel network in the YRD
The number, series, length, fractal dimension, drainage density and drainage efficiency of the tidal channel network were selected to characterize the morphological evolution of the tidal channel network at the delta scale and the regional scale (three sub-regions, namely the erosion area, the oilfield area and the siltation area). The results show that the morphological characteristics of tidal channel network vary with the study scale. At the delta scale, the tidal channel network shows a simplified development pattern. At the regional scale, the tidal channel network in the erosional and oilfield areas presents a simple development pattern, while that in siltation area presents a complex development pattern. The main driving forces of tidal channel network morphological change are tidal flat erosion (siltation) and human reclamation activities. By analyzing the driving factors, it can be seen that human reclamation is the main driving factor affecting the morphological change of tidal channel network at the delta scale. At the regional scale, reclamation is the main driving factor of tidal channel network morphological change in the erosional and oilfield areas, and siltation of tidal flat is the main driving factor of tidal channel network morphological change in the siltation area.
(2) The longitudinal hydrologic connectivity index was constructed to identify the variation of the longitudinal hydrologic connectivity of the tidal channel network of the delta, and to identify the damaged and stable areas of the longitudinal hydrologic connectivity of the delta
The results show that the longitudinal hydrological connectivity firstly increases and then decreases with time. In the 2018, the combined hydrologic connectivity at the delta scale had decreased by 85 percent from its historic peak, and the erosion area had nearly tripled. Silted areas have been reduced by 40%. From the perspective of space, the key nodes and key edges that have important influence on the longitudinal hydrological connectivity of the delta are distributed in several large tidal channels in the erosion area and the siltation area, and the tidal channels in the oilfield area have little influence on the connectivity of the whole delta. From the perspective of time, the influence of tidal channel network on the hydrological connectivity of the whole delta tends to weaken. In the 2018, the key nodes and key edges that have important influence on the hydrological connectivity in the erosion region almost disappeared. This indicates that the longitudinal hydrological connectivity of the region is damaged. The key nodes and key edges in the siltation area remain relatively stable during the study period, indicating that the hydrological connectivity in the area remains stable and is a stable area of hydrological connectivity. From the analysis on driving factors, relcamation is the main driving factors on the variation in hydrological connectivity on the whole scale of the delta, but the early reclamation will not affect its integrated hydrological connectivity degree, only after the exploitation in more than 40%, further increasing the proportion of exploitation in will significantly reduce tidal creek the vertical degree of hydrological connectivity of the network.
(3) The lateral hydrological connectivity index was constructed to explore the change mode of lateral hydrological connectivity of the delta 
The results show that the lateral hydrological connectivity between tidal channel and tidal flat in the YRD is not high on the whole, and the lateral connectivity potential is different in different areas. The closer the tidal channel is, the higher its connectivity potential is. Based on the analysis of the lateral hydrologic connectivity index, it is found that the lateral hydrologic connectivity varies little with time at the delta scale. At the regional scale, the lateral hydrologic connectivity of the erosion area increases, while that of the siltation area decreases, and there is no obvious difference in the overall change of the oilfield area. Further classification of the connectivity model shows that the response area of the total lateral connectivity decreases with time at the delta scale. The area of the highly connected region remains stable while that of the low connected region decreases with time. At the zonal scale, the total connected response area of erosion zone and oilfield zone decreases with time, and the damage is significant. The lateral total connected response area of the silted area is stable with time. After the hot spot analysis and trend analysis of the lateral hydrological connectivity model, it is concluded that the lateral hydrological connectivity model of does not form a continuous connectivity model in time and space. The "oscillation" model is the dominant model of lateral hydrological connectivity of the YRD.
(4) Establishing the evaluation model of functional connectivity, quantify the variation rule of functional connectivity under different structural connectivity changes, and propose the stability principle of hydrological connectivity
The tidal channel network in the hydrologic connectivity damaged area and the stable area is selected to study. The results show that the decrease of the hydrological connectivity will lead to the increase of the functional connectivity. Specifically, if the connectivity of the hydrological structure is damaged, the functional connectivity within the subnets will increase, the degree of traffic sharing between subnets will decrease, and the uncertainty of the choice of transmission path of the traffic between subnets will increase. There is a time lag between the change of structural connectivity and the change of functional connectivity of tidal channel network, that is, the decrease of structural connectivity will not immediately lead to the increase of functional connectivity. By contrast, the tidal channel network with stable structural connectivity shows a stable trend in terms of intra-subnet connectivity, inter-subnet traffic sharing, information sharing and uncertainty in the process of inter-subnet traffic transmission. Based on the negative entropy theory, the stability principle of the hydrological connectivity is discussed. The results show that the structural connectivity of tidal channel network controls the functional connectivity of tidal channel network, and further controls the stability of the functional connectivity of tidal channel network. Specifically, the stability of tidal channels with damaged hydrological connectivity decreases. When the structural connectivity is damaged to a certain extent, its stability will further decline and enter an unstable state. The stability of tidal channels with stable structural connectivity is stable. The number of structural connectivity units controls the functional connectivity of tidal channel network and is a key indicator of its hydrological connectivity stability.
(5) The impacts of longitudinal and lateral hydrological connectivity changes on plankton community and macrobenthos in salt marsh were analyzed, and the ecological impact of damaged hydrological connectivity on the community was clarified
The characteristics of plankton community in tidal channel were also different with the longitudinal hydrological connectivity of tidal channel network. The damage of the longitudinal hydrologic connectivity did not cause significant changes in the diversity of plankton community, nor did the change of synchronicity between communities, but it significantly reduced the density of plankton community. Therefore, the stability of vertical hydrological connectivity helps to improve the density of plankton community. Studies on macrobenthos in the intertidal zone of the YRD show that the dominant species of macrobenthos community in the intertidal zone of the YRD are different with the study area, and there are temporal and spatial differences. The density and biomass of macrobenthos were higher in the eroded area than in the silted area, but the biodiversity in the eroded area showed a decreasing trend, while the biodiversity in the silted area remained stable. The loss of lateral hydrologic connectivity had little effect on the density and biomass of macrobenthos, but significantly reduced the biodiversity of macrobenthos.
(6) The optimization model of damaged hydrological connectivity is proposed and simulated
Integration of the front research results, hydrological connectivity damage decreased the benthic animal biodiversity, the stability of the hydrological connectivity can improve the biodiversity, by increasing the tide channel network outlets to optimize the damaged longitudinal hydrological connectivity and lateral hydrological connectivity, it stabilizes hydrological connectivity and enhances macrobenthic biodiversity. Combined with the current situation of tidal channel network and the number of structural units needed for its stability, seven scenarios were set up for optimization simulation. The results show that with the increase of outlet points of tidal channel network, the number of nodes and edges increases synchronically, and the number of key nodes and key edges also increases. With the increase of outlets, the connectivity of the structure increases linearly. The relationship between the functional connectivity of tidal channel network and the number of outlet points varies with the functional connectivity. There is also a significant positive correlation between the number of outlet and the stability of hydrological connectivity, and the stability gradually increases with the increase of outlets count. Therefore, the optimization of the number of outlets of tidal channel network can promote the increase of the connectivity degree of the vertical hydrological structure and weaken the functional connectivity intensity, and the optimization of the vertical hydrological connectivity can also optimize the lateral hydrological connectivity.