Abstract:

Aims: Soil bacteria are key components in biological soil crusts (BSCs). They play irreplaceable functional roles in arid and semi-arid ecosystems. Loess sandy-hilly area of northwestern Shanxi Province is typical fragile ecosystem. However, the effects of vegetation and BSCs on soil bacterial diversity in this area remain unknown. 

Method: Algal and moss crusts under three vegetation types (grassland, shrubland, and woodland) were chosen in this area. Soil bacterial community and their key environmental regulating factors were explored by high-throughput sequencing and environmental analysis. The results showed that: (1) Vegetation and BSCs jointly affected soil nutrients. Shrubs and Woodland had significant enrichment effects on soil nutrients. BSCs succession significantly increased the nutrient content in the soil but decreased the soil pH value. (2) Both the BSCs and vegetation types influenced on the α-diversity, relative abundances of key species, and community structure of bacterial communities. Higher species richness was observed in forestlands for both algal and moss crusts. For the same BSC type, significant differences in bacterial relative abundances at the phylum and order levels were observed between grasslands and shrublands (P < 0.05). (3) Mantel tests revealed soil pH, soil organic carbon (SOC) and total nitrogen showed significant relation with bacterial community dissimilarity (Bray- Curtis) (P < 0.05), while α- diversity of bacterial community represented strong association with organic carbon and ammonium nitrogen (P < 0.01). 

Conclusion: Vegetation and BSCs co-modulate soil nutrients and bacterial diversity in northwestern area of Shanxi Province, with pH, SOC, TN and NH_₄^⁺-N being key community drivers. The results enhance our understanding of bacterial diversity in BSCs and provide scientific evidence for a deeper comprehension of ecosystem biodiversity and functional stability in this area.

Key words: Loess sandy-hilly area, Vegetation change, Biological soil crusts, Bacterial community diversity, Environmental factors