在自然状态下，湖泊的沼泽化过程极为缓慢，往往需要上千年甚至更长时间。 但在气候变化和人类活动的强烈干扰下，湖泊沼泽化速度显著加快，极大损害了 其生态服务功能，严重缩短了湖泊寿命。在诸多湖泊类型中，草型浅水湖泊生态 服务功能优良，更易被人类开发利用，也正因如此，这类湖泊表现出了严重的沼 泽化问题。为了减缓草型浅水湖泊的沼泽化趋势，使其在维持区域生态平衡、保 护生物多样性、改善环境效益等方面继续发挥重要作用，必须全面深入地揭示沼 泽化演替规律、阐明其驱动机制，并在此基础上探索建立有效调控模式。 本论文选取我国北方地区草型浅水湖泊的代表-白洋淀为研究对象。过去三 十年来，研究区水位不断下降、淀底逐渐抬升、水生植物大量生长且结构单一， 表现出典型的沼泽化现象。针对上述问题，论文以回答和解决草型浅水湖泊沼泽 化问题为出发点和落脚点，以沼泽化发展变化过程为研究主线，在生态学、水文 学、湿地学、环境化学等相关学科理论的指导下，结合国内外相关文献、历史资 料和实地调研结果，综合运用数理统计、模拟试验、遥感模型、景观格局分析等 手段，开展了一系列研究工作，并取得了相应进展，具体阐述如下： （1）揭示了草型浅水湖泊沼泽化演替的一般规律。在唯物辩证法中事物发展 变化基本理论的指导下，以国际国内同类湖泊的演替模式为参照，以演替过程中 水生植物群落组成结构变化为依据，将草型浅水湖泊的沼泽化过程划分为五个演 替阶段，明确了推动演替的主导环境因子，并结合生态阈值曲线和高斯曲线确定 了主导因子在不同阶段的阈值，建立了沼泽化演替的一般模式。 （2） 阐明了沼泽化过程的驱动机制。以物理、化学、生物过程为切入点，分 析了不同生态过程对沼泽化的驱动作用。针对物理过程，在小区尺度上利用人工 降雨试验模拟了淀内坡面流产沙过程；在淀区尺度上开展土壤侵蚀空间模拟，估 算出淀内年均侵蚀产沙量；结合多年水深数据和光谱反射率数据建立了水深遥感 回归方程，并据此计算出淀底高程的年均升幅。针对化学过程，通过采集沉积物 柱状样品，分析了碳、氮、磷等生源要素在不同淀区的积累特征及其主要来源； 在一个生长周期内对白洋淀优势水生植物种营养含量的变化进行连续监测，明确 了元素在植物-沉积物-水体间的循环转化机制；通过对不同淀泊的统计分析，证明了富营养化和沼泽化的反馈关系。针对生物过程，分析了优势物种对主导环境 因子的响应关系，并模拟了不同环境梯度上植物的生长过程；以挺水植物根状茎 为研究对象，利用分解袋法模拟了六个龄级根状茎的分解过程，并估算了其对生 物累积的贡献；通过分析鉴定沉积物中生物残体的来源，明确了不同淀区的生物 累积特征并估算了其对淤积的整体贡献；构建人类活动强度指数并分析了人类活 动压力对群落演替的驱动作用。对驱动机制的研究结果表明：淀内产沙是加快白 洋淀沼泽化过程的主要原因，受到降雨侵蚀和土地无序开发的影响，淀内年均产 沙量达到 520 万立方米，过去三十年来淀底年均抬升幅度约为 2.6 厘米，导致大 量淀泊和水道淤浅淤干，水文连通性和水量调蓄能力大幅减弱；水生植物在元素 循环中起到重要作用，其吸收积累元素的超过 70%又归还到环境中，富营养化和 沼泽化在一定程度上表现出正反馈关系，中富营养淀泊的沼泽化程度最为严重； 生物累积对总淤积量的平均贡献为 20.6%，人类活动强度对水生植物群落沼泽化 演替具有显著影响。 （3） 预测了白洋淀沼泽化发展变化的趋势。根据研究区社会经济统计资料， 建立生态保护优先、保持现状、经济发展优先等三种发展情景，并以此为据预测 了未来四十年研究区的沼泽化趋势。三种情景对应的淀底平均淤积升幅分别为 0.9 厘米、2.6 厘米、2.9 厘米；到 2055 年，对应的高程超过 7.5 米的淀泊分别为 18 个、11 个和 7 个。当淀区处于多年平均水位时，生态保护优先情景下淤干淀 泊（水深小于 0 米）仅有两个，分别位于淀区的西北部和西南部，而淀区中部、 东部和南部大部分淀泊的平均水深均在 1.5 米以上，淀内村庄的撤并整合以及相 关保护措施的落实是导致这一空间变化的重要原因；而在现状情景和经济发展优 先情景下，淤干淀泊更多集中在淀区中部和南部等人口稠密、经济规模较大的村 落周边。 （4） 构建了白洋淀沼泽化治理的综合调控模式。针对物理过程，以恢复淀泊 水文连通、增强调蓄能力为目标，根据图论分析方法，将白洋淀独特的“淀泊水道”结构概化为“节点-边”构成的水系网络；在不同发展情景和水量情景下， 计算淤积量对淀泊调蓄水量的影响，并根据白洋淀防洪调度规划确定洪水风险淀 泊；结合土地利用规划确定调节淀泊的位置，借助最小成本距离方法确定风险淀 泊与调节淀泊的连通路径，优化研究区网络结构。针对生物过程，利用多目标规划方法对水生植物群落优化配置，计算出不同约束条件下水生植物群落生物量的 最佳配比，促进水生植物在减缓沼泽化趋势、削减水体营养盐含量、以及保证农 民收入水平等方面发挥重要作用。

The process of lake terrestrialization is very slow under natural states, which always needs thousands of years or longer. However, climate changing and humans‘ activities with strong interference have obviously accelerated the lake terrestrialization. The ecosystem service function has been greatly damaged and the life of lakes has been shortened seriously. Macrophyte-dominated shallow lake shows an excellent ecosystem service function in many lake types, which makes more accessible to be developed and utilized by humans. Therefore, this type of lakes shows serious problems of terrestrialization. In order to slow down the terrestrialization trend of macrophyte-dominated shallow lake, and therefore in continuing to play an important role in maintaining regional ecological balance, protecting biodiversity and improving environmental benefits, the succession law of terrestrialization should be revealed and the driving mechanisms should be clarified deeply and comprehensively. On this basis, effective control mode is exploring to be established. In this thesis, Lake Baiyangdian, a representative of macrophyte-dominated shallow lake in North China was selected as the research object. Over the past three decades, the constantly falling water levels, gradually raising pond bottom and abundantly growing aquatic plants with single structure, showed a typical terrestrialization phenomenon of the study area. Aiming at the above problems, this paper is to delay terrestrialization as a goal, and the the development process of terrestrialization is seen as the main line. According to the guidance of related disciplines theory with ecology, hydrology, wetlands and environmental chemistry, follows by combing with related literatures in domestic and overseas, historical data and field investigation results. The mathematical statistics, simulation test, remote sensing models and landscape pattern analysis methods have been used integrated, several researches have carried out as (1) General succession laws of terrestrialization in macrophyte-dominated shallow lake have been revealed. The conclusion was under the guidance of process theory and stage theory in materialistic dialectics and threshold theory in ecology. The succession mode of similar international and domestic lakes was to be a reference, and the quantity change of aquatic plant community structure in succession process was to be a basis. The terrestrialization process of macrophyte-dominated shallow lake has been divided into five succession stages. The dominant environmental factors for promoting succession have been clarified. The threshold of domestic factors in different stage has been determined by combining the ecological threshold curve with Gauss curve. The general succession mode of terrestrialization has been established. (2) The driving mechanism of terrestrialization process has been illustrated. Physical, chemical and biological processes as the starting point, it analyzed the driving role of different ecological processes on terrestrialization. For physical processes, sediment process in the slope has been simulated by artificial rain test in the plot scale. Soil erosion spatial model in the lake scale has been carried out, and the average annual sediment yield in the lake has been estimated. Combining with data of water depth with many years and spectral reflectance, a fathoming regression equation has been established, and the average annual increase in the end-point elevation has been calculated. For chemical processes, main source of biogenic elements (C, N, P) and the accumulation characteristics in different regions of lake have been analyzed by collecting sediment core samples. The circulation and conversion mechanisms of elements among plant-sediment-water have been cleared by continuously monitoring the nutritional content change of aquatic species in a life cycle. The feedback relationship between eutrophication and terrestrialization has been proved by statistical analysis in different ponds. For biological processes, the response relationship between the dominant species and the major environmental factors has been analyzed. The growth of plants on different environmental gradients has been simulated. Taking the emergent plants rhizomes as research object, the decomposition process of the six age classes‘ rhizomes has been simulated by Litter bag technique, and its contribution to bio-accumulate has been assessed. By analyzing and identifying the sources of sediments in biological residues, the bio-accumulation characteristics in different lake regions have been cleared and the overall contribution of bio-accumulation to the siltation has been assessed. Human activity intensity index has been constructed, and the driving effects of human activities pressure to the community succession have been analyzed. The results of the drive mechanisms showed that the main reason of speeding up Baiyang pond terrestrialization was lake sediment. Affecting by rainfall erosion and land disorder development, the annual sediment yield has reached 200,000 cubic meters in lake. And the lake bottom annual has been raised about 2.6 cm over the past three decades. Therefore a large number of the lakes and waterways have been silted, and the hydrological connectivity and the flow regulation ability have been significantly weakened. Aquatic plants have played an important role in the cycling of elements, and over 70% of the absorption of accumulation elements has returned to environment. Eutrophication and terrestrialization have showed a certain positive feedback relationship, and ponds with middle degree eutrophication have showed the most serious terrestrialization. Average contribution of bioaccumulation to the total deposition amount was 23%, and human activities have showed a significant impact on the terrestrialization succession of aquatic plant communities. (3) The development trend of terrestrialization in Lake Baiyangdian has been predicted. According to the social and economic statistical data, three kinds of development situations have been constructed, which is ecological protection preference, maintaining current status and economic development preference. The terrestrialization trend of the study area in the next four decades has been forecasted. The average increases of silting in pond bottom were 0.9 cm, 2.6 cm, and 2.6 cm under the three scenarios. Until 2055, the amounts of ponds with height of more than 7.5 meters will be 18, 11 and 7 respectively. When pond area is at the average water level, the amount of dry pond with water depth of less than 0 meters was only two under the ecological protection priority scenario, which located in the northwest and southwest of pond area respectively. And the average water depth of most of ponds in meters central, eastern and southern area of the pond are is above 1.5 meters. The space change has been caused mainly by village removal and merger integration and the implementation of related protection measurements. In the present situation and economic development priority scenario, the dry ponds have been concentrated in the village surroundings on the central and southern of pond area, with a dense population and a large scale economy. (4) The comprehensive control framework for delaying terrestrialization has been established. For the physical process, aiming to restore the lake hydrology linking and to enhance the storage capacity, the ‗pond-waterway‘ net structure of study area has been generalized into ‗node-edge‘ drainage network by graph analysis method. In the different development situation and water amount, the effects of sediment siltation on pond adjustable storage have been calculated. The flood risk pond has been determined according to the flood control scheduling plan in study area. The position of adjustable pond has been determined by combining with land use planning. The linking path between risk ponds and adjustable ponds has been determined by the minimum cost distance method, and the basic model of network optimization has been established. For biological processes, the best proportion of aquatic plant community biomass under different constraint conditions has been calculated by using the multi-objective programming method to optimize aquatic plant community. Above all will play an important role in promoting aquatic plants to slow down the terrestrialization trend and cut down the water nutrient content, and finally to guarantee the farmers' income level.