Biological soil crusts mitigate shallow landslide and erosion risks on loess slopes under intense dry-wet cycles: mechanisms and disaster prevention implications

To address the high risk of shallow landslides and hydraulic erosion on Loess Plateau slopes induced by intense dry-wet cycles, this study explored the disaster mitigation effect and mechanism of biological soil crusts (BSCs) through indoor scaled slope model tests. Taking bare soil (BS) and BSC-covered soil as research objects, we monitored volumetric water content, matric suction, and cone penetration resistance, and analyzed BSC microstructure. Results showed that BSCs, via their “surface fiber network + deep EPS-soil particle porous structure”, reconstructed shallow water distribution: the 0–30 cm layer served as the core water retention zone, the 20 cm “connecting layer” first reached full saturation then rebounded in matric suction, and the 30–50 cm layer maintained near-saturation—effectively avoiding excessive saturation-induced slope instability. BSCs enhanced soil shear strength by 25%–30% through EPS-boosting aggregate cohesion, with the 2–6 cm layer (most sensitive to dry-wet cycles) showing significant strength adaptation via fiber network “swelling-shrinkage”. BSCs prevent shallow loess instability through “ecological-mechanical synergy”, providing a cost-effective, eco-friendly technical approach for loess slope disaster prevention and mitigation.