The microbial communities in soils are crucial in the maintenance of ecosystem processes in arid areas such as Thi-Qar Province, southern Iraq, and their seasonal relationship is not clear. This paper is the first high-resolution examination of the seasonal alterations of soil microbial communities in Thi-Qar by the 16S rRNA gene (V4 region) and multivariate statistics. An extreme summer (45.2 ℃) and mild winter (17.8 ℃) in 2023-2024 are surveyed in ten sampling sites (five agricultural, five non-agricultural) that are located in the summer and winter respectively. The physicochemical characteristics of the soils (pH, salinity, moisture, organic matter) and the diversity of the microorganisms are examined. The findings indicated a strong decrease of 25% in microbial diversity (Shannon index) in summer with a sharp change in community structure. The abundance of actinobacteria in the summer soils (42% relative abundance) is higher than that of proteobacteria (48% in the winter). Redundancy Analysis (RDA) showed that temperature is by itself sufficient to account 45.2 % of all the variation in microbial community. These results demonstrate the high sensitivity of soil microbiomes with climatic variations in arid areas and a possibility to work out climate-resistant soil management technologies.

The microbial communities in soils are crucial in the maintenance of ecosystem processes in arid areas such as Thi-Qar Province, southern Iraq, and their seasonal relationship is not clear. This paper is the first high-resolution examination of the seasonal alterations of soil microbial communities in Thi-Qar by the 16S rRNA gene (V4 region) and multivariate statistics. An extreme summer (45.2 ℃) and mild winter (17.8 ℃) in 2023-2024 are surveyed in ten sampling sites (five agricultural, five non-agricultural) that are located in the summer and winter respectively. The physicochemical characteristics of the soils (pH, salinity, moisture, organic matter) and the diversity of the microorganisms are examined. The findings indicated a strong decrease of 25% in microbial diversity (Shannon index) in summer with a sharp change in community structure. The abundance of actinobacteria in the summer soils (42% relative abundance) is higher than that of proteobacteria (48% in the winter). Redundancy Analysis (RDA) showed that temperature is by itself sufficient to account 45.2 % of all the variation in microbial community. These results demonstrate the high sensitivity of soil microbiomes with climatic variations in arid areas and a possibility to work out climate-resistant soil management technologies.