Terrace wall reinforcement through herbaceous root architecture: Dichotomous vs. herringbone branching patterns

Research Hypothesis:
The study hypothesized that the root systems of specific herbaceous plant species could significantly enhance terrace wall stability in mountainous agricultural regions by improving soil shear strength through root-soil interlocking and mechanical reinforcement. It aimed to evaluate the effectiveness of three plant species—Alopecurus aequalis, Hedyotis chrysotricha, and Dicranopteris dichotoma—in stabilizing terrace walls, focusing on their root architectural traits and mechanical properties.

Data Overview:
The research employed a direct shear test to quantify soil shear strength under four conditions: bare soil and soils reinforced by the root systems of the three plant species. Additionally, Partial Least Squares Structural Equation Modeling (PLS-SEM) was used to analyze the relationships between root architecture, soil properties (structure and moisture content), and terrace wall stability. Key metrics included soil shear strength (kPa), root topological index (TI), fractal dimension, and root tensile strength.

Notable Findings:

Hierarchical Enhancement of Soil Shear Strength:
Bare soil: 16.73 kPa
Alopecurus aequalis: 28.83 kPa (+72.42% increase)
Hedyotis chrysotricha: 42.53 kPa (+154.27% increase)
Dicranopteris dichotoma: 55.58 kPa (+232.32% increase)
Dicranopteris dichotoma demonstrated the highest stabilization efficiency, with a 232.32% increase in soil shear strength compared to bare soil.
Key Factors Influencing Stability:
Root Architecture: The topological index (TI) (λ = 0.95) and fractal dimension (λ = 0.93) emerged as critical contributors to root-soil interlocking, with TI identified as the primary stabilizing factor.
Soil Structure: Directly influenced stability (β = 0.28, p < 0.05).
Soil Moisture Content: Negatively impacted stability (β = -0.50, p < 0.001), highlighting the need for effective drainage.
Mechanical Traits and Synergistic Effects:
Root architecture indirectly enhanced stability by improving root mechanical properties (β = 0.70, p < 0.001).
Fine roots (<0.9 mm diameter) were critical for increasing tensile strength and reinforcing soil aggregates.
Data Interpretation and Implications:

Species Selection: Prioritize species with high TI (e.g., Dicranopteris dichotoma) to maximize root-soil interlocking.
Root Optimization: Promote fine root development to enhance tensile strength and soil aggregate stability.
Drainage Systems: Implement drainage to mitigate moisture-induced reductions in shear strength.
Soil Aggregate Preservation: Maintain soil structure to support root growth and mechanical reinforcement.
Methodological Rigor:

Statistical Analysis: One-way ANOVA confirmed significant differences in soil shear strength between vegetation types. PLS-SEM elucidated synergistic effects, with model adequacy validated by a goodness-of-fit (GOF > 0.70).
Tools: Data analysis and visualization were performed using R (v4.3.2) and IBM SPSS Statistics V22.0.