Surface soil physical properties and stability: Determined by biological soil crust type and driven by aridity in the desert regions of Northwest China

Biological soil crusts (biocrusts) development is a fundamental factor affecting stability by wind prevention, sand fixation, and desert surface soil stability enhancement, and aridity is an important driver for altering soil stability in drylands. The physical properties of biocrusts and binding sand quantity (BSQ) are important indicators for characterizing the stability of desert soil. The relationships between biocrust physical properties and BSQ are not clear, which is not conducive to a comprehensive understanding of the ecological functions of biocrusts. The different successional stages of biocrusts in the arid region of Northwest China were selected to study their physical properties and BSQ. The physical properties and BSQ of the different types of biocrusts were measured. The responses of the physical properties and BSQ of different types of biocrusts to aridity were analyzed. The results showed that the physical properties and BSQ increased significantly with biocrust development. The thickness, roughness, compressive strength, shear strength, and BSQ of the biocrusts show a significant increasing trend with the development and increase of biocrusts and coverage. BSQ and compressive strength increased with increasing thickness and roughness. Physical properties, physical multifunctionality (P-SMF), and BSQ of different biocrust types showed significantly different trends with increasing aridity. The results of structural equation modeling also revealed that the P-SMF and BSQ had different responses with increasing aridity. This study contributes to a comprehensive understanding of biocrust structure and function, particularly for wind prevention and sand fixation, as well as surface stability. This study provides a new methodology and new ideas for determining the distribution and surface stability of biocrusts and is highly important for land management and conservation in drylands.