The differentiation of soil bacterial communities along a precipitation and temperature gradient in the eastern Inner Mongolia steppe

Understanding the differentiation of soil bacterial communities under precipitation and temperature gradients is crucial for assessing the impacts of environmental filters on ecosystem structure and function. Here we investigated spatial variations of bacterial communities along a precipitation and temperature transect in the eastern Inner Mongolia steppe, China. The aims are to understand the biogeographic pattern and key drivers shaping soil bacterial communities along the transect. Our results showed that the soil bacterial community along the 451-km transect exhibited the distance-decay relationship, decreasing in community similarity with geographic distance. Obvious changes in the bacterial community structure occurred at an annual precipitation from 215 to 261 mm, which was close to the boundary between arid and semi-arid systems. The relative abundances of Proteobacteria, Bacteroidetes, and Acidobacteria increased with precipitation, while those of Actinobacteria, Chloroflexi, and Gemmatimonadetes decreased. Environmental filtering was observed to be the key in shaping bacterial biogeographic patterns, and climate conditions exert indirect effects on soil bacterial communities mainly through direct effects on soil properties. Soil pH and plant coverage were important to soil bacterial communities in both arid and semi-arid steppes. Our findings provided insights for understanding the linkages among geographic distance, environmental filters, and soil bacterial communities in Eurasian steppe ecosystems.