Objective The aims were to explore the effects of a single short-term controlled rainfall event on the physical and chemical properties of soils at different depths and the structural composition of bacterial communities in the Stipa krylovii grassland of Inner Mongolia during diverse seasons of the following year, and to identify the key driving factors. This endeavor was not only conducive to a more profound understanding of the pivotal roles that soil bacterial communities played within the grassland ecosystem but also provided a robust theoretical framework for elucidating the response mechanisms of bacterial communities to environmental fluctuations. Such insights were deemed crucial for advancing the knowledge in the field of ecological science and had the potential to inform more effective strategies for the conservation and management of grassland ecosystems.

Method The Stipa krylovii grassland in Inner Mongolia was selected as the research site. Meticulously designed simulated precipitation experiments were carried out, which involved two treatment conditions: the normal precipitation was increased by 50% and decreased by 50%. Subsequently, high-throughput sequencing technology was applied to systematically investigate the impact of short-term rainfall on the bacterial community. Multiple analytical methods were then used to identify and analyze the main driving factors related to the observed alterations.

Results In the context of both the increased and decreased rainfall treatments, it was noted that the contents of total organic carbon (TOC) and available nitrogen (AN) were generally higher than those in the control group. Specifically, the contents of TOC, AN, available phosphorus (AP), and soil temperature (ST) were found to have the highest values within the 0 ~ 10 cm soil layer. Notably, the AN content in spring was observed to be greater than that in both summer and autumn. No alterations in the composition of bacterial phyla were triggered by the increased and decreased rainfall treatments. Actinobacteria was shown to have the highest abundance, ranging from 58.01% to 72.69%, and this abundance was gradually increased as the soil depth increased. In contrast, an opposite trend was exhibited by Proteobacteria and Acidobacteria across different soil layers. Moreover, no significant influence on the bacterial Alpha diversity was exerted by the rainfall treatments. It was determined that summer and the 0 - 10 cm soil layer had the most significant impacts on the bacterial Alpha diversity. The Anosim analysis clearly revealed that the bacterial community structures in the 0 ~ 10 cm soil layer during spring, summer and autumn under the increased and decreased rainfall treatments as well as the control group were significantly different from those of other treatment groups (P < 0.01). The RDA analysis further indicated that TOC and pH were respectively identified as the principal soil physical and chemical factors that influenced the abundance of the soil bacterial community and the bacterial diversity.

Conclusion Short-term controlled precipitation has no significant impact on the composition of the bacterial community and bacterial Alpha diversity. Season and soil layer have extremely significant effects on bacterial Alpha diversity. TOC is the main factor influencing the abundance of the bacterial community, and pH is the main factor affecting bacterial Alpha diversity.