Root distribution in willow brush mattresses: Experimental framework and preliminary findings

¹ Karlsruhe Institute of Technology, Institute of Soil Mechanics and Rock Mechanics, Germany
² Department of Geotechnical Engineering, Federal Waterways Engineering and Research Institute, Karlsruhe, Germany

^* Corresponding author: shan-shan.li@kit.edu

Abstract

Willow brush mattresses are widely used for riverbank stabilization, but research on root distribu- tion in soils of varying conditions remains limited following their establishment. To bridge this gap, this study developed a specially designed cultivation setup featuring a modular structure and highly controllable variable settings, along with a methodology for root distribution analysis. Preliminary results indicate that root growth over two months enhanced water retention in upper soil layers. In turn, root growth was strongly influenced by soil compaction, which was categorized as loose, medium-dense, and dense. In loose sand, roots penetrate deeper, while in medium-dense and dense sand, they are restricted to shallow layers, with maximum penetration depths of 45 cm and 30 cm, respectively. Further analysis showed that in loose sand, root mean diameter, Root Area Ratio (RAR), and dry mass remain nearly constant with depth, whereas in dense sand, these parameters decrease progressively. In contrast, medium-dense sand exhibits non-linear trends, likely due to the presence of extensive lateral fine roots. This study presents a novel laboratory methodology for willow cultivation, enabling parametric analyses to optimize the application of willow brush mattresses for sustainable riverbank stabiliza- tion. Additionally, it advances practical approaches for analyzing root distribution, addressing challenges in studying soil-root interactions under varying soil conditions.