Data of biocrusts model tests

Most parts of the Loess Plateau are located in semi-arid climatic zones, where the impacts of short-duration intense rainfall are significant. To explore the control effect and mechanism of biological soil crusts (BSCs) on the shallow surface layer of loess under short-duration intense rainfall conditions, bare soil (BS) and BSC-covered soil from the semi-arid region of the Loess Plateau were selected as the research objects. Indoor scaled slope model tests were conducted to simulate the alternating environment of short-duration intense rainfall and drought. The variation characteristics of soil volumetric water content, matric suction, and cone penetration resistance during the dry-wet cycle were analyzed, and the underlying mechanism was revealed by combining the microstructure of BSCs. The results showed that, relying on the layered structure of "surface fiber network + deep EPS-soil particle porous structure", BSCs could reconstruct the water distribution in the shallow loess layer and improve the water retention capacity of the soil, with the area within 30 cm depth being the core zone for water retention. The soil at 20 cm depth, serving as a key layer for "connecting the upper and lower parts" of water, first reached complete saturation and then its matric suction increased; while the soil at 30-50 cm depth-maintained a near-saturated state. Meanwhile, BSCs enhanced the cohesion of soil particle aggregates through extracellular polymeric substances (EPS), thereby improving the soil shear strength. The soil at 2-6 cm depth was most sensitive to dry-wet cycles in terms of strength, which was attributed to the "swelling-shrinkage" effect of the surface fiber network. In conclusion, BSCs can prevent the instability of the shallow loess surface layer through the "ecological-mechanical synergy" effect, providing theoretical support and technical references for loess slope protection.