Putting down roots: Afforestation and bank cohesion of Icelandic Rivers

• Published in: River research and applications 2023-11, Vol.39 (9), p.1669-1681
• Main Authors: Rathburn, Sara L., Eysteinsson, Þröstur, Sæmundsson, Þorsteinn, Kemper, John T., Wieting, Celeste D., Friedman, Jonathan M.
• Format: Article
• Language: English
• Subjects: Afforestation; Bank erosion; Betula pubescens; Cohesion; Critical components; Forbs; Forest protection; Forests; Human settlements; Land acquisition; Land area; National forests; Planting; Riparian land; Riparian vegetation; Riverbanks; Rivers; Roots; Sandy loam; Sediment; Sediments; Seedlings; Soil erosion; Stabilizing; Stream banks; Vegetation; Woodlands; Woody plants
• ISSN: 1535-1459; 1535-1467
• DOI: 10.1002/rra.4172

Riparian vegetation is widely recognized as a critical component of functioning fluvial systems. Human pressures on woody vegetation including riparian areas have had lasting effects, especially at high latitude. In Iceland, prior to human settlement, native downy birch woodlands covered approximately 15%–40% of the land area compared to 1%–2% today. Afforestation efforts include planting seedlings, protecting native forest remnants, and acquiring land areas as national forests. The planted and protected nature of vegetation along rivers within forests provides a unique opportunity to evaluate the various taxa within riparian zones and the channel stabilizing characteristics of the vegetation used in afforestation. We investigated bank properties, sediment textures, and root characteristics within riparian zones along four rivers in forests in Iceland. Bank sediment textures are dominantly sandy loam overlying coarser textures. Undercut banks are common because of erosion of the less cohesive subsurface layer. Quantitative root data indicate that the woody taxa have greater root densities, rooting depths, and more complex root structures than forbs or graminoids. The native downy birch has the highest root densities, with