| Summary: | Biocrust is widely distributed on land surfaces worldwide, it is especially important in arid and semi-arid areas with serious soil erosion; however, the impact of biocrust on vegetation soil coupling in complex topography has not been reported. This study revealed the variation of biocrust coverage in different slope direction and gradient, and the fluctuation of vegetation and subsoil physicochemical properties mediated by it. The SEM (Structural equation modeling) further investigated the effects and pathways of biocrusts on soil-vegetation coupling conditions. The results indicated that the degree of coupling of the sunny slope showed a trend of gradual dispersion with a starting point of 1 as the slope decreased, whereas the coupling degree of the shady slope showed an overall process of gradual aggregation towards 1. In addition, the SEM showed that the moss on sunny slopes affected degree by nourishing vegetation (47%) and the effect of soil on coupling degree is more obvious (23%) on shady slopes. As for lichen system, it affected the coupling degree (27%) by itself on sunny slopes, and it further influencing coupling on shady slopes through the mediation of vegetation (54%). Our research results provide a theoretical of the coupling of soil and vegetation in middle slope (45°) is best in two directions, and provide a reference for the segmented management of soil erosion under continuous slope changes.
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