Biological soil crusts reduce soil microbial diversity and potential function in alpine meadows of the Qinghai-Tibet Plateau

Biological soil crusts (BSCs) are one of the important functional components in some grassland ecosystems. However, it remains largely unknown how BSCs affect soil microbial communities in alpine ecosystem, especially in Qinghai-Tibet Plateau (QTP). We selected two contrasting surface cover types in the northeastern QTP—normal Kobresia meadow (NM) and biocrusts-covered meadow (BM), and the 16S rRNA and internal transcribed spacer sequencing were used to explore soil microbial diversity, community composition, and potential function. Our results showed that soil microbial ACE, Shannon, and Chao indices in BM were significantly lower than that in NM (P < 0.05). Principal coordinate analysis indicated distinct bacterial community structures across two meadow types (P < 0.05). The dominant bacterial and fungal phyla were Actinobacteriota (25.44%) and Basidiomycota (51.40%), respectively. Furthermore, NM exhibited greater microbial network complexity and higher abundance of potential nitrogen-fixing bacterial. The aromatic compound degradation and cellulolysis were generally exhibiting higher levels in NM. The abundance of pathogens and symbiotic bacteria varies among different meadow types, with symbiotic bacteria being significantly enriched in BM. The changes in soil microbial communities were primarily associated with soil total nitrogen, total carbon, and organic matter. Null model and beta-NTI results indicated that bacterial community was primarily dominated by deterministic processes, while fungal community followed stochastic processes. These findings indicated that the presence of BSCs reduces soil microbial diversity and function in alpine meadows, which provide the theoretical support for degraded ecosystem restoration in the alpine ecosystems. • Biocrust reduced soil microbial alpha diversity compared to normal meadow. • Soil microbial networks were more complex in normal meadow than in biocrust meadow. • Soil bacteria were influenced by soil total nitrogen, carbon, and organic matter. • Soil fungi were significantly influenced by soil clay content.