Changes in microbial communities in biological soil crusts along an altitudinal gradient in the northeastern Qinghai-Tibet plateau

Abstract

Biological soil crusts (BSCs) cover approximately 12 % of the earth's terrestrial surface and play vital ecological roles in various dry habitats. However, most research on BSCs has focused on deserts in arid and semi-arid regions, with limited studies on BSCs under sensitive, fragile, and cold conditions, such as those found in the Qinghai-Tibet Plateau. Notably, investigations into the complete successional stages of BSCs in these regions are exceedingly rare. In this study, we examined four successional stages of BSCs across five sites at elevations ranging from 2862 to 4274 m in the northeastern Qinghai-Tibet Plateau. High-throughput sequencing was used to analyze the bacterial, fungal, and archaeal communities in the soil, and their diversity, interactions, spatial distribution patterns, and influencing factors were investigated. Our results indicated that in alpine degraded grassland ecosystems, the altitude gradient played a significant role in shaping the distribution patterns of microbial communities during the succession of BSCs. At lower elevations (2862–3405 m), the successional patterns of α-diversity for the three microbial communities were relatively consistent. In contrast, α-diversity patterns at higher altitudes showed greater variability. Differences in bacterial composition between high-altitude areas (3760 m and 4274 m) increased with the development and succession of BSCs, while the differences between low-altitude areas (2862 m and 3405 m) showed opposite trend. The differences in fungal composition across all altitude regions gradually decreased with the succession of BSCs. Additionally, bacterial and fungal composition demonstrated more distinct altitudinal zonation characteristics compared to archaea. Within the bacterial, fungal, or archaeal communities, mutualistic interactions were stronger than competitive interactions, facilitating adaptation to the harsh high-altitude environment. Furthermore, mean annual precipitation, mean annual temperature, pH, and sand content collectively influenced the microbial community distribution patterns in alpine degraded grassland ecosystems. Our research provides scientific references for the distribution and resource protection of BSCs in the Qinghai-Tibet plateau.