滨海盐沼非稳定流动力机制及对植被生长影响研究

Salt marshes at the ocean-land interface are very important wetland ecosystems, with various ecological functions, such as maintaining coastal biodiversity, improving the nearshore water quality and mitigating global warming. However, over the past few decades, the development activities of human beings in coastal areas have led to sharp decrease of marsh area worldwide, and meanwhile greatly weakened their ecological functions. The pore water flow is an important process that determines the formation and evolution of salt marshes, and underpins their ecological functions. So far, people’s understanding of such process and its relation with marsh plant response is still far from comprehensive, particularly lacking in-depth investigations of the widely existing unstable flow in marsh soils. This program aims to combine laboratory experiments and numerical modelling to analyse the dynamic characteristics of unstable flow in salt marshes under the effects of multiple factors, to identify the mechanism and critical condition of its occurrence, and to quantify its impact on marsh plant growth. This program will help improve people’s understanding of subsurface flow in salt marshes and its connection with the ecological functions of marshes, and provide theoretical guidance for protecting and restoring coastal salt marshes and constructing artificial wetlands.

位于海-陆交界带的盐沼是极为重要的湿地系统，拥有维持沿海生态多样性、改善海域水质、缓解全球变暖等生态功能。然而，人类在海岸带的开发活动已经导致过去几十年内世界各地的盐沼面积急剧下降，并使得其生态功能退化。孔隙水动力过程是决定盐沼形成和演变以及支撑其生态功能的最主要因素之一。目前，人们对盐沼孔隙水动力过程及其与植被响应关系的认识还不够完善，尤其缺乏关于盐沼土壤中普遍存在的非稳定流的研究。本项目拟采用物理沙槽实验和数值模拟相结合的手段，分析不同因素共同作用下盐沼土壤中非稳定流的动力特征，明确非稳定流在盐沼土壤中的产生机制及临界条件，量化非稳定流对盐沼植被生长的影响。该项研究将有助于完善人们对盐沼孔隙水动力过程及其与盐沼生态功能关联的认识，为保护修复滨海盐沼以及建设人工湿地提供理论指导。

滨海盐沼是位于海陆交界带的重要湿地系统，拥有诸多生态功能，例如：为水生动植物提供栖息地从而维持滨海生态多样性、净化沿海水质、吸收存储二氧化碳进而缓解全球变暖、保护内陆地区免受海平面上升威胁等。盐沼的形成及演变很大程度上受制于盐沼水动力以及溶质（包括盐分）迁移过程。因此，开展滨海水动力机制的研究有助于制定有效的盐沼保护及修复措施，并为合理开发利用盐沼资源提供指导。针对已有研究的不足之处，本项目所开展的主要研究内容包括：（1）利用物理沙槽实验和数值模拟相结合的手段研究了复合因子作用下的滨海盐沼以及地下河口中的非稳定流动力机制和溶质运移特征；（2）优化地下水数值模拟SUTRA-MS，基于物理实验完成模型验证，开展参数分析从而判断滨海盐沼中非稳定流的产生条件；（3）对地下水数值模拟SUTRA进行二次开发得到新模型SUTRASET，利用数值模拟研究主控因子耦合作用下滨海盐沼土壤中以及土壤表层的盐度分布时空变化特征，进而预测不同耐盐植被的生长和分布趋势。相关研究成果揭示了滨海盐沼中水动力及溶质迁移过程的动态性、复杂性，有助于人们深入认识盐沼的基本功能。