Spatial distribution pattern across multiple microbial groups along an environmental stress gradient in tobacco soil

Background It has become commonplace to explore the spatial distribution patterns of microbial communities in natural ecosystems. However, few have looked at the responses of community diversity, structure, and assembly processes from different microbial groups to changes in environmental stress caused by altitude.Purpose We investigated the spatial and biogeographical patterns of different microbial groups, including bacteria, fungi, and protists, from tobacco soil along an altitudinal gradient to evaluate the influence of geographic distance and environmental stress on microbial distribution pattern.Methods DDR (distance decay relationship) model was calculated to evaluate the spatial distribution pattern. Then, NCM (neutral community model) and two null-modelling-based approaches, NST (normalized stochasticity ratio) and iCAMP (the infer community assembly mechanism by phylogenetic-bin-based null model analysis), were used to reveal the importance of stochastic and deterministic processes to microbial community assembly by utilizing high-throughput sequencing data.Result Bacterial community a-diversity decreased significantly (P < 0.05) with increasing environmental stress. Moreover, all communities exhibited a significant DDR pattern (P < 0.001), with the slope of bacteria (0.146) being significantly higher (P < 0.05) than that of fungi (0.059) and protists (0.060). The results of NCM and the two null-modelling-based approaches revealed the importance of stochastic processes to bacterial (83.4%) and protist (69.9%) communities, which were primarily shaped by drift and dispersal limitation, respectively; meanwhile, deterministic processes were important to the fungal community (53.7%). Additionally, we found a significant correlation between the assembly process and geographic distance (P < 0.05).Conclusion Our study provides a complementary perspective to the study of multiple hierarchical groups across different spatial scales (i.e., horizontal and vertical scales).