The role of biological soil crusts in vascular plant recruitment in the Loess Plateau region, China

Globally, biological soil crusts (BSCs) are crucial ecosystem components that perform essential functions important to ecosystem stability. However, the potential mechanisms of BSC's effect on vascular plant recruitment and establishment are largely unknown. Furthermore, few studies have considered BSC-vascular plant analyses in conjunction with BSC microenvironments, seed traits, and plant life stages simultaneously. Thus, we chose six typical plants with different seed traits on the Loess Plateau and conducted a growth chamber experiment to evaluate the effects of BSC types, disturbance, seeding positions, and moisture on seed germination, survival, and seedling growth. We also explored the effects of BSC presence and disturbance on seedling emergence through field investigation. The results indicated that the main effects of the four factors, BSC type, disturbance, seeding location, and moisture, and their two- and three-dimensional interactions had significant effects on the performance of most of the studied species. Disturbance and wetting treatments with shorter watering intervals promoted the performance of most plants, and moisture could modify the effect of BSCs on plants. The effect of BSCs on plant performance was related to seed traits and plant life stage and the presence of the BSC promotes the growth of the plants when it reaches the survival stage. In field observations, we found that the number of seedling species was lower on BSCs compared to bare lands and that the number of species on broken crusts was greater than on intact crusts; while seedling density on bare land was significantly higher than it in BSC patches.