Biological Soil Crusts Shift the Evaporation Front to Modulate Deep Soil Water Dynamics

Aims Biological soil crusts (BSCs) play key roles in dryland surface stabilization and water conservation, but their regulation of deep soil hydrology and field applicability remain unclear. Methods This study integrated indoor soil column experiments, microstructural analysis, modeling, and 23-day field monitoring (Loess Plateau rainy season) to explore cyanobacteria-moss BSCs’ ecohydrological effects. Results Results showed BSCs actively shift the evaporation front downward—a pattern validated indoors and in the field. Laboratory data: BSCs reduced evaporation by ~ 75% vs. bare soil (BS), formed a 30 cm water accumulation zone via an EPS-mediated hydraulic barrier, and lowered saturated hydraulic conductivity by three orders of magnitude. Field data: BSCs stabilized the evaporation front at 45–50 cm (BS: 70→40 cm upward recession), mitigated drought-period water content fluctuations (surface variation − 40% vs. BS), and reduced extreme rainfall-induced deep soil over-saturation (15 cm moisture peak: 48.3% vs. 62.5% in BS). Conclusions This work confirms BSCs as dynamic ecohydrological engineers, providing insights for dryland restoration and soil conservation.