Riparian Soil Development Linked to Forest Succession Above and Below Dams Along the Elwha River, Washington, USA

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• 作者：Laura G. Perry ; Patrick B. Shafroth ; Steven S. Perakis
• 关键词：dams ; fluvial disturbance ; forest stand age ; geomorphic surfaces ; nitrogen cycling ; nutrient concentrations ; nutrient pools ; riparian forest communities ; soil texture ; succession
• 刊名：Ecosystems
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：20
• 期：1
• 页码：104-129
• 全文大小：
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Ecology; Plant Sciences; Zoology; Environmental Management; Geoecology/Natural Processes; Hydrology/Water Resources;
• 出版者：Springer US
• ISSN：1435-0629
• 卷排序：20

文摘

Riparian forest soils can be highly dynamic, due to frequent fluvial disturbance, erosion, and sediment deposition, but effects of dams on riparian soils are poorly understood. We examined soils along toposequences within three river segments located upstream, between, and downstream of two dams on the Elwha River to evaluate relationships between riparian soil development and forest age, succession, and channel proximity, explore dam effects on riparian soils, and provide a baseline for the largest dam removal in history. We found that older, later-successional forests and geomorphic surfaces contained soils with finer texture and greater depth to cobble, supporting greater forest floor mass, mineral soil nutrient levels, and cation exchange. Forest stand age was a better predictor than channel proximity for many soil characteristics, though elevation and distance from the channel were often also important, highlighting how complex interactions between fluvial disturbance, sediment deposition, and biotic retention regulate soil development in this ecosystem. Soils between the dams, and to a lesser extent below the lower dam, had finer textures and higher mineral soil carbon, nitrogen, and cation exchange than above the dams. These results suggested that decreased fluvial disturbance below the dams, due to reduced sediment supply and channel stabilization, accelerated soil development. In addition, reduced sediment supply below the dams may have decreased soil phosphorus. Soil δ15N suggested that salmon exclusion by the dams had no discernable effect on nitrogen inputs to upstream soils. Recent dam removal may alter riparian soils further, with ongoing implications for riparian ecosystems.