半荒漠-绿洲区湿地系统动态变化的关键生态阈值识别

The ecological threshold is a kind of “qualitative change point” and “qualitative change track” in ecosystem maintenance. With complex, polymorphism, and the very strong scale effect, it also is a scientific problem that must be involved in ecological system stability, ecological security and risk assessment, environmental change and eco-economic research. As the ecological environment problems research tends to be precise, the ecological threshold is becoming a global hot issue. In this study, semi desert-oasis area as the target region, using the regional survey, typical habitat gradient survey, simulation experiments, model simulation and other research techniques, from each macro, meso and micro level, the transition zone sensitive study on ecological threshold of wetland system is carried out. Based on the identification of key factors such as water, salt and sand, dynamic process and succession identification, a correlation analysis and model simulation research of environmental factors and ecological elements are also carried out in different gradient situation of water and land, water and salt and water and sediment. After strives to keep on approaching the ecological indicators thresholds when wetland type qualitative change occurred, the key ecological threshold of wetland system changes is established based on physical and chemical and ecological indicators, then a breakthrough strives to be achieved on the model selection and parameter correction. The research results will help to break down the situation of natural wetland ecological status evaluated by water quality index, and provide new research ideas and intervention points for wetland system and ecological economic system research and restoration ecology.

生态阈值是生态系统维持中的“质变点”和“质变轨迹”，是生态系统稳定性、生态安全与风险评估、环境变化和生态经济研究中绕不开的科学问题，具有复杂性、多态性和很强的尺度效应，随着生态环境问题研究的精准化，正在成为全球性的热点问题。本研究以半荒漠-绿洲为靶区，采用面上调查、典型生境梯度调查、模拟实验、模型模拟等研究手法，从宏观、中观和微观三个层面上，开展过渡性区域敏感性极强的湿地系统生态阈值研究。在进行湿地系统水、盐、沙等关键要素、动态过程和演替关系识别的基础上，对水陆、水盐和水沙梯度界面开展环境要素与生态要素的关联分析和模型模拟，力求不断逼近湿地类型质变时的生态要素指标阈限，建立基于理化和生态指标的湿地系统变化关键生态阈值，并力争在模型筛选和参数修正上有所突破。研究成果有助于打破以水质指标评价自然湿地生态状态的局面，为湿地系统乃至生态经济系统研究和恢复生态学等提供新的研究理念和介入点。

生态阈值是生态系统维持中的“质变点”和“质变轨迹”，是生态系统稳定性、生态安全与风险评估、环境变化和生态经济研究中绕不开的科学问题，具有复杂性、多态性和很强的尺度效应，随着生态环境问题研究的精准化，正在成为全球性的热点问题。本研究以半荒漠-绿洲为靶区，采用面上调查、典型湿地定位半定位监测、模拟实验、模型模拟等研究手法，从宏观、中观和微观三个层面上，开展过渡性区域敏感性极强的湿地系统生态阈值研究。分别选择鄂尔多斯台地内流闭流区盐湖、宁夏平原黄河滩涂与草滩湿地、宁夏南部黄土高原堰塞湖群等典型湿地，进行目标湿地植被类型与组成结构、土壤理化性质和土壤微生物种群多样性等诸特征的识别，湿地类型的动态变化过程识别和影响因素分析，水、盐、沙的生境梯度与基于群落综合响应的关键阈值识别，并在此基础上进行相应的风险阈值评价模型模式建构。研究结果初步解释了水域、沼泽、滩涂草甸等湿地类型下植被的生态指标与水、盐、沙、养分等土壤环境要素指标间的互作与响应关系；以湖滩盐生草甸植被为范例，筛选出土壤含水量、全盐、Na+、CO22-、粒径、速效钾、碱解氮及速效磷等8个强约束性指标，在群系组水平上界定了禾草草甸、肉质耐盐草甸、苔草草甸和杂类草草甸的生态阈值区间和阈值量，并以此作为构建相应湿地系统动态过程和演替关系模型变量的依据。本研究还在区域和生境两个尺度上解读了半干旱-绿洲区湿地类型和湿地植被类型的分布规律，剖析了气候、土壤、水环境、地形、人文活动等因素对局地湿地系统发育和隐域植被分布的驱动力与作用强度。本研究的理论意义在于其建立了湿地多元生态要素的相互关系，有助于打破以水质等生态要素指标评价生命系统健康状况的局面，为湿地系统乃至生态经济系统研究和恢复生态学等提供新的研究理念和介入点；实践意义在于其对典型湿地过程动态的量化解析，可以为湿地生态修复、资源合理利用、自然生态保护等提供科学指导。

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