Soil bacterial communities in alpine wetlands in arid Central Asia remain stable during the seasonal freeze–thaw period

Under the background of climate change, freeze–thaw patterns tend to be turbulent: ecosystem function processes and their mutual feedback mechanisms with microorganisms in sensitive areas around the world are currently a hot topic of research. We studied changes of soil properties in alpine wetlands located in arid areas of Central Asia during the seasonal freeze–thaw period (which included an initial freezing period, a deep freezing period, and a thawing period), and analyzed changes in soil bacterial community diversity, structure, network in different stages with the help of high-throughput sequencing technology. The results showed that the α diversity of the soil bacterial community showed a continuous decreasing trend during the seasonal freeze–thaw period. The relative abundance of dominant bacterial groups (Proteobacteria (39.04%–41.28%) and Bacteroidota (14.61%–20.12%)) did not change significantly during the freeze–thaw period. At the genus level, different genera belonging to the same phylum dominated in different stages, or there were clusters of genera belonging to different phylum. For example, g_Ellin6067, g_unclassified_f_Geobacteraceae, g_unclassified_f_Gemmatimonadaceae coexisted in the same cluster, belonging to Proteobacteria, Desulfobacterota and Gemmatimonadota respectively, and their abundance increased significantly during the freezing period. This "adaptive freeze–thaw" phylogenetic model suggests a heterogeneous stress resistance of bacteria during the freeze–thaw period. In addition, network analysis showed that, although the bacterial network was affected to some extent by environmental changes during the initial freezing period and its recovery in the thawing period lagged behind, the network complexity and stability did not change much as a whole. Our results prove that soil bacterial communities in alpine wetlands are highly resistant and adaptive to seasonal freeze–thaw conditions. As far as we know, compared with short-term freeze–thaw cycles research, this is the first study examining the influence of seasonal freeze–thaw on soil bacterial communities in alpine wetlands. Overall, our findings provide a solid base for further investigations of biogeochemical cycle processes under future climate change.