How Plant Roots and Soil Structure Improve Roadside Slope Stability

Jenn Hoskins
16th September, 2025

How Plant Roots and Soil Structure Improve Roadside Slope Stability

Results indicate that Amorpha fruticosa (2), maximized soil aggregate stability through robust mycelial development and protein secretion, significantly outperforming the intermediate Lespedeza bicolor (3) and the structurally coarser but functionally limited Swida alba (1), thereby validating the critical role of coordinated belowground traits in slope stabilization.

Composite: Natural Science News / CC BY-SA. [Sources]
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Key Findings

  • In northeastern China’s expressway slopes, the shrub Amorpha fruticosa (AFL) significantly improved soil stability compared to other species
  • Soil stability relies on a combination of strong fungal networks and sticky soil proteins, with AFL exhibiting the best combination of both
  • Steeper slopes reduced the effectiveness of the sticky soil proteins, making the physical structure of the fungal networks more important for preventing erosion
Highway slopes in cold regions face significant erosion risks, threatening infrastructure. Soil stability is paramount, and recent research from the Heilongjiang Institute of Construction Technology, the Institute of Geographic Sciences and Natural Resources Research, CAS, and Rodale Institute[1] investigated how the root systems of certain shrubs contribute to preventing this erosion. The study focused on three shrub species – Amorpha fruticosa (AFL), Lespedeza bicolor (LBT), and Swida alba (SAO) – growing on slopes with differing steepness in northeastern China. The core issue is that soil erosion isn’t simply about the loss of particles; it’s about the breakdown of soil structure. Healthy soil isn’t just loose dirt, but a complex network of aggregates – clumps of soil particles held together by organic matter and, crucially, the interwoven threads of fungal mycelium. These aggregates are more resistant to being washed away by water. Previous work has established that fungal networks play a vital role in forming and stabilizing these aggregates, acting as a kind of natural glue[2]. The challenge, however, is understanding how different fungal species contribute and how environmental factors influence this process. The researchers measured the stability of water-stable aggregates – how well they held together when exposed to water – alongside the amount of glomalin-related soil protein (GRSP). GRSP is a sticky protein produced by fungi and is a key indicator of fungal activity and its contribution to soil binding. They also meticulously analyzed the traits of the mycelium itself, essentially examining the physical characteristics of the fungal networks. The results clearly showed that AFL outperformed LBT and SAO in stabilizing soil, exhibiting significantly higher aggregate stability on both gentle and steep slopes. This suggests that AFL possesses characteristics that make it particularly effective at erosion control. Importantly, the study identified a strong relationship between the amount of extractable GRSP, mycelial traits, and aggregate stability, explaining up to 95.1% of the variation on gentle slopes. This indicates a “synergistic trait-based mechanism” where fungal activity (measured by GRSP) and the physical structure of the mycelium work together to reinforce the soil. However, the researchers found that this relationship wasn’t constant. On steeper slopes, the effectiveness of GRSP diminished. This suggests that the physical act of holding the soil together – the scaffolding provided by the mycelium itself – became more important than the biochemical “glue” when the forces acting to pull the soil apart were greater. This is a crucial finding, demonstrating a “slope-dependent reallocation between physical scaffolding and biochemical adhesion”. This study builds upon earlier research highlighting the difficulty of accurately quantifying fungal contributions to soil structure[3]. By focusing on specific mycelial traits and linking them directly to soil stability, the researchers were able to move beyond simply measuring fungal biomass to understanding how fungi function in this context. The ability to extract mycelium efficiently, as demonstrated in a separate study[3], is a prerequisite for this type of detailed analysis. The findings have practical implications for slope restoration projects. Selecting shrub species like AFL, with its robust mycelial network, could significantly improve erosion control efforts, particularly in cold regions. This research provides a mechanistic basis for these selections, moving beyond empirical observations to a deeper understanding of the biological processes at play. The study emphasizes the importance of considering environmental conditions – in this case, slope steepness – when choosing appropriate species and designing effective erosion control strategies.

EcologyPlant ScienceMycology

References

Main Study

1) Mycelial traits and GRSP in enhancing soil stability on cold region highway slopes: Comparative effects of three shrub species

Published 15th September, 2025

https://doi.org/10.1371/journal.pone.0332483

Related Studies

2) Fungal-mediated soil aggregation as a mechanism for carbon stabilization.

https://doi.org/10.1093/ismejo/wraf074

3) An improved method for extraction of soil fungal mycelium.

https://doi.org/10.1016/j.mex.2023.102477


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