[Response of Soil Bacterial Community Structure to Precipitation Change in Grassland of Loess Plateau].

As the main participants of ecosystem functions, the response of microorganisms to variations in soil moisture caused by the changes in precipitation amounts should be quantified to evaluate the impact of climate change on semi-arid ecosystems. For this purpose, a two-year simulation of the changes in the rainfall patterns was conducted on the Loess Plateau, and five precipitation treatments (80% and 40% decrease in precipitation, D80, D40; natural precipitation, NP; 40% and 80% increase in precipitation, I40, I80) were set up. The results showed that: ① Compared with NP, the carbon-to-nitrogen ratio (C/N) was lower in DP80 or IP80, while it reached the maximum value in I40. The mean C/N value of the 0-20 cm soil layer was 10.76. The microbial biomass carbon to microbial biomass nitrogen ratio (MBC/MBN) varied significantly with the soil layer in the treatments of D80 and I80, and the maximum value was 14.15 in D80. ② In the grassland soil naturally growing on the Loess Plateau, at the phylum level, the dominant phyla were Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria. At the class level, Actinobacteria, Acidobacteria, -Proteobacteria, and Thermomicrobia were predominant. ③ RDA analysis showed that changes in soil dissolve organic carbon (DOC), dissolved organic nitrogen (DON), elemental carbon (EC), and pH values were the main factors affecting the distribution of soil bacteria under the five precipitation treatments in the study area. Overall, 80% increase or decrease in precipitation has a significant impact on soil active organic carbon content and bacterial abundance, especially D80. In conclusion, drought or extreme precipitation may considerably change the active organic matter content and bacterial community diversity and abundance in the soils of the Loess Plateau.