Linking hydroecologic form and function in estuary-wetland systems

将河口湿地系统的水文生态形式和功能联系起来

• 批准号: 1013843
• 负责人: Steven Gorelick
• 金额: $ 39.87万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-11-15 至 2015-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1013843&HistoricalAwards=false
• 关键词: Linking; hydroecologic; form; function; estuary

Estuarine wetlands are being degraded and lost at a tremendous rate worldwide. Yet there is a lack of science to support consistently successful wetland restorations and consequently many restorations fail for unknown reasons. The premise of this research is that the health of an estuary is intimately linked to its surrounding landscape, particularly shore-fringing wetlands. This research will analyze 96 major salt marshes surrounding San Francisco Bay using a combination of field data, remote sensing-based pattern recognition, and flow and transport simulation. The marshes range in age from 10s to 1000s of years old, thus enabling statistical assessment of whether marsh hydroecologic complexity is related to marsh development and age, and whether the range of marsh forms is consistent with theories of natural marsh development. Analysis is aimed at determining the relative importance of surface water residence time as it relates to sediment accretion potential, groundwater and solute residence time as a measure of chemical sequestration potential, surface water-groundwater exchange linking wetlands to the estuary, and plant-water interactions. We test two main hypotheses: 1) Site-to-site variations in estuarine salt marsh channel and vegetation patterns (form) result in site-to-site identifiable variations in wetland processes (function). 2) The cumulative form of the marsh fringe around an estuary functions analogously to the hyporheic zone of a riparian system, enhancing long fluid and solute residence times in the coupled marsh-estuary hydrologic system. The first hypothesis is tested by analyzing a set of contrasting marsh sites. Preliminary analysis suggests at least five classes of hydroecologic forms present in the San Francisco estuary. Representative sites for analysis will be identified from the sample of 96 salt marshes using object-based remote sensing image analysis and statistical characterization of channel and vegetation patterns. Statistical analysis will test if the complexity of marsh form is correlated with site restoration, age, or other characteristics. The second hypothesis is tested using a large-scale model coupling estuarine circulation with surface and near surface hydrology of the estuarine wetland fringe. Groundwater simulation will represent subsurface water storage and exchange with the estuary, subsurface solute migration and mixing, and evapotranspiration. Estuarine flow simulation will represent shallow water flow behavior in the Bay. The coupled model will quantify cumulative estuary-marsh fluid and solute exchange and residence times. The broader impact of this research is an improved scientific framework linking the desirable form of the wetland, which is typically engineered during restoration by constructing shaped channels and planting vegetation, to its function, which involves surface water-groundwater exchange, plant water use, and spatially variable hydrological processes. In addition, estuarine and wetland science and education will benefit from a new database of salt marsh attributes by providing significant educational potential of further estuary-wide comparative analyses. With the assistance of the Stanford School of Earth Sciences outreach coordinator, this work will improve local education and restoration/management resources for San Francisco regional salt marshes through a map-based exploration tool and a set of brochures on salt-marsh hydroecology.

河口湿地正在以惊人的速度退化和消失。然而，缺乏科学来支持持续成功的湿地恢复，因此许多恢复失败的原因不明。这项研究的前提是，河口的健康与其周围的景观密切相关，特别是滨海湿地。这项研究将使用现场数据、基于遥感的模式识别以及流动和运输模拟相结合的方法，分析旧金山湾周围的96个主要盐沼。沼泽的年龄从10s到1000s不等，因此可以统计评估沼泽水文生态的复杂性是否与沼泽发育和年龄有关，以及沼泽形态的范围是否与自然沼泽发育理论相一致。分析的目的是确定地表水停留时间的相对重要性，因为它与沉积物积累潜力、地下水和溶质停留时间作为衡量化学隔离潜力的指标、连接湿地与河口的地表水-地下水交换以及植物-水相互作用有关。我们检验了两个主要假说：1)河口盐沼河道和植被格局(形态)的站点到站点的差异导致湿地过程(功能)在站点到站点之间可识别的变化。2)河口周围沼泽边缘的累积形式类似于河岸系统的潜流带，增加了沼泽-河口耦合水文系统中长时间的流体和溶质停留时间。第一个假设是通过分析一组对比鲜明的沼泽遗址来检验的。初步分析表明，旧金山河口至少存在五种水文生态形式。将利用基于对象的遥感图像分析和河道和植被模式的统计特征，从96个盐沼样本中确定具有代表性的分析地点。统计分析将检验沼泽形态的复杂性是否与遗址恢复、年龄或其他特征相关。利用河口环流与河口湿地边缘地表和近地表水文耦合的大尺度模式对第二种假设进行了验证。地下水模拟将模拟地下水与河口的储存和交换、地下溶质的迁移和混合以及蒸发蒸腾。河口水流模拟将代表海湾内的浅水流动行为。耦合模型将量化河口-沼泽流体和溶质交换的累积时间和停留时间。这项研究的更广泛影响是一个改进的科学框架，将理想的湿地形式与其功能联系起来，后者通常在恢复期间通过修建成形的渠道和种植植被来进行工程设计，涉及地表水-地下水交换、植物用水和空间变化的水文过程。此外，河口和湿地科学和教育将受益于一个新的盐沼属性数据库，它为进一步进行河口范围的比较分析提供了巨大的教育潜力。在斯坦福大学地球科学学院外联协调员的协助下，这项工作将通过一个基于地图的探索工具和一套关于盐沼水生态的小册子，改善旧金山区域盐沼的当地教育和恢复/管理资源。