Effects of water-table and depth on prokaryotic microbiota

Microbial communities are important to ecosystem function and sensitive to hydrological dynamics. However, we lack a predictable understanding of how soil microorganisms respond to water-table drawdown in different depths. Here, we used high-throughput sequencing method to elucidate the responses of prokaryotic communities to the water-table and depth gradients in Zoige Peatlands. Water-level lowering decreased some copiotrophic bacteria (e.g., Bacteriodetes) and increased certain oligotrophs (e.g., Acidobcteria) in their relative abundances, indicating the shifts in microbial life history strategies. From surface layers to deeper layers, most of anaerobic microorganisms (e.g., Chloroflexi, Planctomyctes and NC10) were increased, while most aerobes (e.g., Proteobacteria and Acidobacteria) showed a decreasing trend, suggesting the aerobic processes were changed to anaerobic processes with depth. In addition, both lowering water-table and increasing depth decreased the alpha diversity indices (observed species, Shannon diversity and chao1 index) of prokaryotic communities. Intriguingly, the decreasing trend was more obvious in the subsurface (20-30 cm and 50-60 cm), rather than the surface (0-10 cm). This study reveals that the alterations of water-table and depth in peatlands lead to predictive changes in microbial communities and processes.