Abstract: Soil moisture, which is an important factor affecting ecosystem function, can maintain microbial activity and ultimately change the microbial community by altering vegetation diversity and controlling the diffusion and transport of soil nutrients. To explore the effects of soil water content (SWC) on soil prokaryotic community, we established a study area covering a natural soil moisture gradient and subdivided it into high (HW, 4.80 ± 1.18%), medium (MW, 2.17 ± 0.09%) and low water contents (LW, 1.85 ± 0.14%) in the grassland ecosystem along the south shore of Hulun Lake in Inner Mongolia, China. Environmental factors were determined by field surveys and laboratory analyses. Soil prokaryotes were determined by high-throughput sequencing techniques. Vegetation characteristics and soil physicochemical properties had a significant effect on prokaryotic richness diversity, and SWC was the most important factor influencing prokaryotic richness diversity. In the MW, the number of differential prokaryotes was lowest, and prokaryotic microorganisms had the highest diversity and relative abundance at the phylum level, which may reflect less intrinsic variation and higher overall activity of the prokaryotic community in the MW. In addition, HW and LW had lower prokaryotic diversity and relative abundance at the phylum level, and phenotypic predictions for both groups indicated a more tolerant prokaryotic community. In summary, the prokaryotic community responded significantly to the natural moisture gradients in grassland ecosystems along the south shore of Hulun Lake, and both too high and too low soil moisture increased prokaryotic stress resistance.

Key words: the south shore of Hulun Lake, temperate grassland, natural soil moisture gradient, soil prokaryotic community, phenotypic prediction