Habitat-specific environmental factors regulate the spatial variability of biological soil crust microbial communities on the Qinghai-Tibet Plateau.

Biological soil crusts (BSCs) are an important biological component of the soil surface, covering approximately 12 % of the Earth's land surface. Although BSCs are closely related to habitats, the microbial diversity and spatial variability of BSCs in different ecosystems are still unclear, especially on the Qinghai-Tibet Plateau (QTP), where climate is changeable and habitats are complex. Here, we investigated the diversity, assembly processes, spatial distribution pattern and driving factors of prokaryotic and eukaryotic microbial communities in BSCs in four habitats on the QTP. It was found that habitat-specific environmental factors regulated the composition, diversity and spatial variability of BSC microbial communities. Soil organic carbon and soil water content were the most important factors (R2 = 0.9024, P = 0.001; R2 = 0.8004, P = 0.001) affecting the spatial differences in prokaryotes and eukaryotes, respectively. Under the specific climate of the QTP, the spatial pattern of microbial communities in BSCs was controlled by precipitation rather than temperature. In addition, ecological processes further explained the effects of habitat specificity, and environmental filtering explained microbial community differences better than dispersal limitation. The results of the neutral community model and the normalized stochastic ratio index revealed that the assembly of prokaryotic communities was determined by deterministic processes at the regional scale, and at the local scale, the assembly process was mainly determined by habitat type, while the assembly of eukaryotic communities was determined by stochastic processes at both the regional and local scales. This study provided a scientific reference for the prediction of BSC distribution and resource conservation under future climate change scenarios.

Soil microbe-mediated carbon and nitrogen cycling during primary succession of biological soil crusts in tailings ponds.

Tailings ponds resulting from mining operations have led to serious environmental hazards, and their bioremediation is an area of ongoing exploration. Primary succession represents the starting point of biotic community establishment and development, with soil carbon and nitrogen cycling being critical to this process. To investigate the soil microbial-mediated carbon and nitrogen cycling patterns accompanying primary succession, we selected three types of tailings ponds as study areas and set up sampling sites for different stages of primary succession. The results showed that primary succession promoted microbe-mediated carbon and nitrogen cycling. It also led to improvements in soil nutrient availability and enzyme activity. In primary succession, the main pathways of carbon cycling are 3HP and rTCA, and nitrogen cycling is nitrate assimilation. In the early stages, microbes mediated more anaerobic and microaerobic processes. As succession proceeded, the pattern of microbial contributions to the carbon and nitrogen cycles changed. As succession proceeds, the functional metabolic potential of the carbon cycle gradually rises, while the nitrogen cycle shows a dramatic increase after the accumulation of autotrophic biomass. In addition, we found a positive coupling pattern between the carbon and nitrogen cycles. These findings support the optimization of bioremediation strategies for tailings ponds.