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Aims: Soil organic carbon (SOC) stability greatly affects soil carbon sequestration capacity and carbon emissions, is related to soil bacterial communities, but it remains unclear whether such relationships exist in alpine wetland biogeomorphic succession. Methods: Here, we used a space-for-time approach across hydrological gradients, and alpine wetland succession can be divided into three types: "Swamp" (S), "Swamp Meadow" (SM), and "Meadow" (M) to examine the dynamics change of SOC fractions and bacterial communities. Results: The succession from S-SM-M resulted in decreased SOC stability (SM and M decreased by 18.65% and 31.88% compared to S). Furthermore, the decrease in SOC stability was primarily due to the decrease in soil moisture during succession and moisture-induced changes in bacterial community structure. e.g., the relative abundance of Proteobacteria decreased significantly by 40.99% and 52.87% in SM and M, while the relative abundance of Acidobacteria increased by 43.49% and 185.04% in SM and M compared to S. Co-occurrence network and random forest analyses further identified that changes in keystone taxa of bacteria, including Deltaproteobacteria, Acidimicrobiia, Bacteroidia and Gammaproteobacteria, were associated with SOC stability. Conclusions: In conclusion, bacteria shifted their community composition to reduce SOC stability in response to soil moisture variations during succession, and underscores the importance of identifying keystone taxa that are crucial for maintaining SOC stability. [ABSTRACT FROM AUTHOR]

Although a large number of studies have reported the importance of microbial communities in terrestrial ecosystems and their response to nitrogen (N) application, it is not clear in arid alpine wetlands, and the mechanisms involved need to be clarified. Therefore, the response of the soil microbial community in a swamp meadow to short-term (1 year) N application (CK: 0, N1: 8, N2: 16 kg⋅N⋅hm–2⋅a–1) was studied using 16S/ITS rRNA gene high-throughput sequencing technology. Results showed that N application had no significant effect on soil microbial community diversity, but significantly changed soil bacterial community structure. N1 and N2 treatments significantly reduced the relative abundance of Chloroflexi (18.11 and 32.99% lower than CK, respectively). N2 treatment significantly reduced the relative abundance of Nitrospirae (24.94% lower than CK). Meanwhile, N application reduced the potential function of partial nitrogen (N) and sulfur (S) cycling in bacterial community. For example, compared with CK, nitrate respiration and nitrogen respiration decreased by 35.78–69.06%, and dark sulfide oxidation decreased by 76.36–94.29%. N application had little effect on fungal community structure and function. In general, short-term N application directly affected bacterial community structure and indirectly affected bacterial community structure and function through available potassium, while soil organic carbon was an important factor affecting fungal community structure and function. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first study examining the influence of seasonal freeze–thaw on soil bacterial communities in alpine wetlands. • Diversity, structure and network of soil bacterial community were relatively stable during freeze–thaw period. • "Adaptive freeze–thaw" phylogenetic model of soil bacterial community enhanced resistance. 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. [ABSTRACT FROM AUTHOR]