Diefenderfer Heida L, Borde Amy B, Cullinan Valerie I, Johnson Lyndal L, Roegner G Curtis
Pacific Northwest National Laboratory, Marine and Coastal Research Laboratory, Sequim, WA, USA.
Pacific Northwest National Laboratory, Marine and Coastal Research Laboratory, Sequim, WA, USA; Columbia Land Trust, Vancouver, WA, USA(1).
Sci Total Environ. 2024 Dec 20;957:176799. doi: 10.1016/j.scitotenv.2024.176799. Epub 2024 Oct 10.
Recognition of the habitat values of coastal and floodplain wetlands has inspired research and engineering to restore biological functions after widespread species declines. However, the restoration and management of tidal river floodplains requires a more complete understanding of anthropogenic stressors on hydrogeomorphology and ecological processes. River floodplains near the ocean are affected by localized diking and dredging as well as basin-wide stressors such as dams. We evaluated the effects of stressors versus spatial position, both longitudinal and lateral to the mainstem, using physical and biological response variables in river floodplain wetlands. We categorized historical and modern stressors on the hydrogeomorphic regime of the lower Columbia River and estuary, northeast Pacific coast, including basin-scale management and local impacts. Using this categorization, we analyzed 44 attributes using field-collected data from 50 floodplain wetlands. Attributes represent channels, floods, plant communities, and fish communities. Here we show that plant and fish communities are stratified by position along the estuarine-riverine gradient, in contrast to physical habitat characteristics, which are stratified by stressors on hydrogeomorphic regimes and in some cases the lateral distance from the mainstem river on tributaries. Spatial position relative to water-level dynamics and salinity more strongly affect the biota than does stressor history. Stressor effects were greatest on the geomorphology observed in formerly diked, now reconnected wetlands and in wetlands with a history of dredged material placement; historically diked sites had anomalously deep channels with larger cross-sectional areas while sites with dredged material had shallow channels and lower levels of organic carbon in sediment. In wetlands subject only to landscape-scale stressors such as flow alterations by dams, organic carbon levels were higher. These findings provide natural resource managers with opportunities to enhance similarity to natural conditions and better understand future wetland evolution from different baselines of stressor history and river position.
对沿海和洪泛平原湿地栖息地价值的认识激发了相关研究与工程，以在物种普遍减少后恢复其生物功能。然而，潮汐河漫滩的恢复和管理需要更全面地了解人为压力源对水文地貌和生态过程的影响。靠近海洋的河漫滩受到局部筑堤和疏浚的影响，同时也受到诸如大坝等流域范围压力源的影响。我们利用河漫滩湿地中的物理和生物响应变量，评估了压力源相对于空间位置（包括相对于干流的纵向和横向位置）的影响。我们对东北太平洋海岸哥伦比亚河下游和河口的水文地貌状况的历史和现代压力源进行了分类，包括流域尺度管理和局部影响。利用这一分类，我们分析了从50个河漫滩湿地实地收集的数据中的44个属性。这些属性代表河道、洪水、植物群落和鱼类群落。我们在此表明，与物理栖息地特征不同，植物和鱼类群落沿河口 - 河流梯度按位置分层，物理栖息地特征是按水文地貌状况的压力源分层，在某些情况下按支流与干流的横向距离分层。相对于水位动态和盐度的空间位置对生物群的影响比压力源历史的影响更大。压力源对以前筑堤、现在重新连通的湿地以及有疏浚物料放置历史的湿地中观察到的地貌影响最大；历史上筑堤的地点有异常深的河道且横截面面积较大，而有疏浚物料的地点河道浅且沉积物中的有机碳含量较低。在仅受诸如大坝导致的水流变化等景观尺度压力源影响的湿地中，有机碳含量较高。这些发现为自然资源管理者提供了机会，以增强与自然条件的相似性，并从压力源历史和河流位置的不同基线更好地理解未来湿地的演变。
