Abiotic filters that interact with wetland plant communities along tidal–fluvial gradients are highly dynamic, and understanding their quantitative thresholds and relationships to interspecific competition is important during an era of sea‐level rise and watershed hydrologic change. Yet, landscape‐scale studies of major coastal rivers from the river mouth to the head of tide, such as this study, remain rare. Here, we develop a new predictive framework for estuarine–tidal river research and management using a river‐specific low‐water datum and the wetland inundation indicator SEV_g, the growing‐season sum exceedance value of hourly surface‐water depth. The distribution and variability of the wetland species pool (n = 203) on the 234 river kilometer (rkm) lower Columbia River and estuary floodplain are described for the first time. 4,940 quadrats at 50 marshes were surveyed (2005–2016). Throughout the estuarine–tidal river system, SEV_g was well suited to describe the wetland inundation regime and its variability based on the combination of longitudinal river position and elevation. SEV_g increased significantly landward. Two primary wetland inundation regimes were identified: the seaward‐tidal, usually greatest during the winter months, and landward‐fluvial, greatest during the growing season. Nearest the ocean, salinity is the abiotic factor limiting species richness and non‐native species. Farther upriver, the daily, seasonal, and interannual variability of the wetting and drying cycle encourage disturbance‐tolerant species and non‐natives and limit the number of hydrophytes and total vegetative cover. Hence, the average between‐year similarity of site‐scale areal cover significantly decreased landward. Hierarchical cluster analysis indicated five vegetative groups and five ecohydrologic zones between rkm 0 and 234 were discriminated with 76 significant species–zone associations. All zones had unique indicator species. Species with high indicator values were Carex lyngbyei throughout the estuarine zones, and Eleocharis palustris, Sagittaria latifolia, and the invasive non‐native Phalaris arundinacea in the upper estuarine and lower, middle, and upper tidal river zones (IV > 0.90). Competition from C. lyngbyei nearest the ocean and P. arundinacea in the tidal river was associated with reduced species richness when total cover was >65%. This framework of filters informs the design and prediction of future wetland plant communities on coastal river floodplains.

中文翻译：

---

沿河口至潮汐河梯度的湿地植物群落的生态水文学

与生物多样性过滤器沿着潮汐-河流梯度相互作用的非生物过滤器是高度动态的，因此在海平面上升和流域水文变化的时代，了解其定量阈值以及与种间竞争的关系非常重要。但是，像这样的研究，从河口到潮头的主要沿海河流的景观规模研究仍然很少。在这里，我们使用特定于河流的低水位数据和湿地淹没指标SEV _g（每小时地表水深的增长季节总和值）为河口-潮河研究和管理开发了新的预测框架。该湿地物种池的分布和变异性（ñ = 203）首次描述了在234河公里（rkm）下游的哥伦比亚河和河口洪泛区。2005年至2016年，对50处沼泽地中的4,940个四足动物进行了调查。在整个河口-潮汐河流系统中，SEV _g非常适合描述湿地的淹没状态及其基于河流纵向位置和海拔的组合的变化性。SEV_克显着增加陆运。确定了两种主要的湿地淹没方式：向海潮汐，通常在冬季月份最大，而向陆水潮，在生长季节最大。最接近海洋的盐度是限制物种丰富度和非本地物种的非生物因素。在更上游，湿润和干燥周期的每日，季节性和年际变化会鼓励耐受干扰的物种和非本地物种，并限制水生植物的数量和总的植物覆盖度。因此，站点规模区域覆盖的年平均相似度显着降低了陆地面积。层次聚类分析表明，在rkm 0和234之间有5个植物群和5个生态水文区带，与76个重要的物种-区域关联区分开。所有区域都有独特的指示剂种类。整个河口区域的Carex lyngbyei，河口上部和潮汐河下部，中部和上部潮汐河带中的Eleocharis palustris，Sagittaria latifolia以及侵入性非原生的Phalaris arundinacea（IV> 0.90）。当总覆盖率> 65％时，来自最靠近海洋的C.lyngbyei和潮汐河中的P. arundinacea的竞争与物种丰富度降低有关。该过滤器框架为沿海河洪泛区未来湿地植物群落的设计和预测提供了依据。