Spatial distribution of biological soil crusts on the slope of the Chinese Loess Plateau based on canonical correspondence analysis

- Relationship between BSCs distribution and environment factors is revealed by GIS, GS and CCA.
- Soil type, aspect, vegetation and solar elevation at 08:00 significantly influence BSCs' development.
- BSCs show a differentiation in hillslope, and are continuously in sandland but sporadically in loess.

Biological soil crusts (BSCs) are a living ground cover widely distributed in arid and semi-arid regions, and providing important ecological functions in arid and semi-arid ecosystems. An understanding of the spatial distribution patterns of BSCs is foundational for the scientific management of this resource. In this study, a typical slope was selected from a small watershed, Liudaogou, in the wind-water erosion crisscross region of the Loess Plateau in northwest China. The spatial distribution characteristics of BSCs and associated influencing factors were investigated at the slope scale via a comprehensive survey and statistical analysis using GS + and CANOCO statistical software. The results showed that the distribution of BSCs was clearly spatially differentiated, with the majority of BSCs widely and continuously distributed in sandy areas at a mean coverage of greater than 30%. Sporadic distribution of BSCs was observed in loess areas mainly at the edges of slopes with a mean coverage of generally less than 20%. The thickness and shear strength of the BSCs did not present significant spatial variation, indicating that these two BSC indices were primarily associated with the age and developmental stage of the BSC which was relatively constant throughout the study area. A canonical correspondence analysis revealed that the spatial distribution of BSCs was closely correlated with soil type, vegetation, surface soil moisture content, slope and aspect. Among these factors, soil type had the most significant impact on BSC distribution and explained 20% of the spatial variation of BSCs. The vegetation community type and topographic wetness index were the secondary influencing factors, and sagebrush (Artemisia desertorum) shrubland and aspen (Populus simonii) woodland provided the most ideal growth environments for BSCs. Other factors such as slope, aspect and solar radiation also affected BSC distribution to a certain degree. Overall, BSCs were clearly selective for topography, soil type and vegetation community and preferentially grew in humid areas with psammophytic plant communities.