Key role of specific above- and below-ground morphological traits of ornamental plant species on preventing freeze–thaw soil erosion on steep slopes

Background and aims: Freeze–thaw cycles in soils occur when water repeatedly freezes and thaws during cold seasons. This process can cause significant soil erosion on steep slopes as thawing leads to topsoil movement and greater susceptibility to environmental erosion. This study investigates freeze–thaw soil erosion on a steep slope and assesses the impact of various ornamental plant species on erosion control and mitigation. Methods: Two shrubs and six herbaceous species were selected based on their morphological root traits from a pool of 73 species and planted on an artificial soil slope. Eroded soil was collected over 19 months. Specific above- and below-ground traits (i.e., plant soil surface coverage during vegetative and dormancy seasons, plant survivorship, very-fine roots length—d < 0.25 mm -, and pioneer roots tensile strength) were analyzed, and a species-specific anti-erosion potential index (AEPI) was developed based on the traits mentioned above. Results: The eight selected plant species showed varying effectiveness in mitigating soil erosion due to the freeze–thaw cycles. Principal component analysis revealed a negative correlation between soil erosion and traits such as vegetative soil coverage, survivorship, and root tensile strength. The AEPI demonstrated a strong negative correlation with soil erosion. Conclusion: Our findings demonstrate that a compact, year-round vegetative cover reduces freeze–thaw soil erosion on steep slopes. At the same time, roots played a less significant role than aboveground vegetation. Additionally, the AEPI has been shown to be a promising tool in plant species selection to be planted for erosion mitigation on artificial slope sites.