Impacts of biological soil crust coverage on evaporation characteristics of two textural soils in the water–wind erosion crisscross region of the Loess Plateau

Biological soil crusts (biocrusts) are widely distributed in the water-wind erosion crisscross region of the Loess Plateau, where they play a pivotal role in regulating the surface water budget. To clarify the impacts of biocrusts on soil evaporation across diverse soil textures under varying scenarios, moss-dominated biocrusts developed on loessial soil and aeolian sandy soil were selected as research subjects for comparative quantitative analysis. By integrating field sampling with simulated evaporation experiments, we quantified soil evaporation characteristics under three experimental treatments: bare soil, undisturbed moss biocrust coverage, and biocrust-covered soil subjected to simulated grazing trampling. Furthermore, we identified the differential effects of topsoil thickness and biocrust coverage on soil evaporation between the two soil textures under moss biocrust cover. The results indicated that the average evaporation rate of aeolian sandy soil was significantly higher than that of loessial soil, regardless of moss biocrust coverage. The average evaporation rate of bare loessial soil was 2.38 g h −1 ; moss biocrusts mitigated evaporation by modifying the surface microstructure, thereby reducing the average evaporation rate by 0.20 g h −1 . Conversely, the average evaporation rate displayed an opposite trend following simulated grazing trampling. Over the entire duration of the simulated evaporation experiment, the average cumulative evaporation of loessial soil was significantly higher than that of aeolian sandy soil under all three scenarios. Under moss biocrust coverage, cumulative evaporation of both soil textures increased with increasing topsoil thickness. The highest evaporation intensity and cumulative evaporation were observed in the absence of topsoil. For biocrusts with topsoil, evaporation intensity decreased as topsoil thickness increased, while cumulative evaporation increased accordingly. These findings advance our mechanistic understanding of biocrust-driven regulation of surface soil water dynamics and provide a scientific basis for soil and water conservation, and desertification mitigation in arid and semi-arid regions.