Permafrost peatlands are a huge carbon pool that is uniquely sensitive to global warming. However, despite the importance of peatlands in global carbon sequestration and biogeochemical cycles, few studies have characterized the distribution characteristics and drivers of soil microbial community structure in forest-peatland ecotones. Here, we investigated the vertical distribution patterns of soil microbial communities in three typical peatlands along an environmental gradient using Illumina high-throughput sequencing. Our findings indicated that bacterial richness and diversity decreased with increasing soil depth in coniferous swamp (LT) and thicket swamp (HT), whereas the opposite trend was observed in a tussock swamp (NT). Additionally, these parameters decreased at 0-20 and 20-40 cm and increased at 40-60 cm along the environmental gradient (LT to NT). Principal coordinate analysis (PCoA) indicated that the soil microbial community structure was more significantly affected by peatland type than soil depth. Actinomycetota, Proteobacteria, Firmicutes, Chloroflexota, Acidobacteriota, and Bacteroidota were the predominant bacterial phyla across all soil samples. Moreover, there were no significant differences in the functional pathways between the three peatlands at each depth, except for amino acid metabolism, membrane transport, cell motility, and signal transduction. Redundancy analysis (RDA) revealed that pH and soil water content were the primary environmental factors influencing the bacterial community structure. Therefore, this study is crucial to accurately forecast potential changes in peatland ecosystems and improve our understanding of the role of peat microbes as carbon pumps in the process of permafrost degradation.

Global climate change is altering the amounts of ice and snow in winter, and this could be a major driver of soil microbial processes. However, it is not known how bacterial and fungal communities will respond to changes in the snow cover. We conducted a snow manipulation experiment to study the effects of snow removal on the diversity and composition of soil bacterial and fungal communities. A snow manipulation experiment was carried out on the meadow steppe in Hulunbuir, Inner Mongolia, China, during the winter period October 2019-March 2020. Soil samples were collected from the topsoil (0-10 cm) in mid-March 2020 (spring snowmelt period). Snow removal significantly reduced soil moisture and soil ammonium concentration. Lower snow cover also significantly changed the fungal community structure and beta diversity. Snow removal did not affect the bacterial community, indicating that fungal communities are more sensitive to snow exclusion than bacterial communities. The relative importance analysis (using the Lindeman-Merenda-Gold method) showed that available nitrogen (AN), soil water content (SWC), total organic carbon (TOC), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) together explained 94.59% of the variation in soil fungal beta diversity, where AN was identified as the most important predictor. These finding provide insights into potential impacts of climate warming and associated reduced snow cover on soil microbial communities and processes.

Background Soil microorganisms in the thawing permafrost play key roles in the maintenance of ecosystem function and regulation of biogeochemical cycles. However, our knowledge of patterns and drivers of permafrost microbial communities is limited in northeastern China. Therefore, we investigated the community structure of soil bacteria in the active, transition and permafrost layers based on 90 soil samples collected from 10 sites across the continuous permafrost region using high-throughput Illumina sequencing. Results Proteobacteria (31.59%), Acidobacteria (18.63%), Bacteroidetes (9.74%), Chloroflexi (7.01%) and Actinobacteria (6.92%) were the predominant phyla of the bacterial community in all soil layers; however, the relative abundances of the dominant bacterial taxa varied with soil depth. The bacterial community alpha-diversity based on the Shannon index and the phylogenetic diversity index both decreased significantly with depth across the transition from active layer to permafrost layer. Nonmetric multidimensional scaling analysis and permutation multivariate analysis of variance revealed that microbial community structures were significantly different among layers. Redundancy analysis and Spearman's correlation analysis showed that soil properties differed between layers such as soil nutrient content, temperature and moisture mainly drove the differentiation of bacterial communities. Conclusions Our results revealed significant differences in bacterial composition and diversity among soil layers. Our findings suggest that the heterogeneous environmental conditions between the three soil horizons had strong influences on microbial niche differentiation and further explained the variability of soil bacterial community structures. This effort to profile the vertical distribution of bacterial communities may enable better evaluations of changes in microbial dynamics in response to permafrost thaw, which would be beneficial to ecological conservation of permafrost ecosystems.

The rapid permafrost degradation caused by climate warming can lead to thermokarst development, which in turn greatly alter soil parameters and impact the soil bacterial communities. However, the effects of thermokarst development on soil bacterial communities largely remain unclear. Here we selected a typical thaw slump in the Qinghai-Tibet Plateau. We classified three microfeatures in the thaw slump areas, i.e., control, slumping and exposed and collected surface 30 cm soils at a depth interval of 10 cm using a soil auger. The results showed that thaw slump decreased soil carbon and nitrogen contents especially for the topsoil (0-10 cm). Thaw slump increased the relative abundance of Gemmatimonadaceae, but decreased the relative abundance of Micrococcaceae. The richness indices including OTU numbers, Ace, Chao 1 and Simpson indices were the largest in the exposed area and lowest in the slumped area, and these trends were opposite to the Shannon index. Correlation analysis revealed that the relative abundance of Micrococcaceae was negatively correlated with moisture, Anaerolineaceae was positively correlated with organic carbon content. The Nitrospira, RB41 and Gemmatimonadaceae were negatively associated with total nitrogen, but Anaerolineaceae and JG30-KF-CM45 were positivity correlated with total nitrogen. C/N ratio was positively correlated with RB41 but negatively correlated with JG30-KF-CM45. We concluded that soil organic carbon, total nitrogen and C/N ratio were the most important factors shaping the bacterial community structure among the three microfeatures. The bacterial community diversity was the highest in the exposed area and lowest in the slumping area. The bacterial structure community was related with total nitrogen, soil organic carbon contents and C/N ratios. Overall, our findings showed thaw slump can decrease soil organic carbon and nitrogen content for the surface soils in the alpine meadow and further change the soil bacterial communities.

Background: Permafrost degradation may develop thermokarst landforms, which substantially change physicochemical characteristics in the soil as well as the soil carbon stock. However, little is known about changes of bacterial community among the microfeatures within thermokarst area. Results: We investigated bacterial communities using the Illumina sequencing method and examined their relationships with soil parameters in a thermokarst feature on the northern Qinghai-Tibetan Plateau. We categorized the ground surface into three different micro-relief patches based on the type and extent of permafrost collapse (control, collapsing and subsided areas). Permafrost collapse significantly decreased the soil carbon density and moisture content in the upper 10 cm samples in the collapsing areas. The highest loading factors for the first principal component (PC) extracted from the soil parameters were soil carbon and nitrogen contents, while soil moisture content and C:N ratios were the highest loading factors for the second PC. The relative abundance of Acidobacteria decreased with depth. Bacterial diversity in subsided areas was higher than that in control areas. Conclusions: Bacterial community structure was significantly affected by pH and depth. The relative abundance of Gemmatimonadetes and Firmicutes were significantly correlated with the first and second PCs extracted from multiple soil parameters, suggesting these phyla could be used as indicators for the soil parameters in the thermokarst terrain.

The Qinghai-Tibetan plateau (QTP) is the largest middle-low latitude permafrost region on earth, while little is known about the microbial community in this area. Here, we investigated the bacterial community in the upper 30 cm soils in the permafrost regions on the central QTP using Illumina sequencing technology. In these soils, the most abundant phyla were Acidobacteria, Proteobacteria, and Bacteroidetes. The depth was significantly correlated with Acidobacteria, Proteobacteria, Nitrospirae, and Gemmatimonadetes. The soil pH and the gravel content were significantly positively correlated with Bacteroidetes. The active layer thickness was significantly correlated with Bacteroidetes and Arabinonates. Although these factors were closely correlated with the relative abundances of specific bacterial phyla, the overall bacterial community structure was mainly affected by pH, soil organic carbon content, and the mean annual precipitation, while the community structure had no significant relationship with the active layer thickness. Our results suggested that the permafrost region on the QTP had greatly heterogeneous environmental conditions, and the responses of microbial communities to permafrost degradation would also be affected by other factors such as precipitation, soil texture and vegetation.

Greenhouse gas (GHG) emissions from thawed permafrost are difficult to predict because they result from complex interactions between abiotic drivers and multiple, often competing, microbial metabolic processes. Our objective was to characterize mechanisms controlling methane (CH4) and carbon dioxide (CO2) production from permafrost. We simulated permafrost thaw for the length of one growing season (90 days) in oxic and anoxic treatments at 1 and 15 A degrees C to stimulate aerobic and anaerobic respiration. We measured headspace CH4 and CO2 concentrations, as well as soil chemical and biological parameters (e.g. dissolved organic carbon (DOC) chemistry, microbial enzyme activity, N2O production, bacterial community structure), and applied an information theoretic approach and the Akaike information criterion to find the best explanation for mechanisms controlling GHG flux. In addition to temperature and redox status, CH4 production was explained by the relative abundance of methanogens, activity of non-methanogenic anaerobes, and substrate chemistry. Carbon dioxide production was explained by microbial community structure and chemistry of the DOC pool. We suggest that models of permafrost CO2 production are refined by a holistic view of the system, where the prokaryote community structure and detailed chemistry are considered. In contrast, although CH4 production is the result of many syntrophic interactions, these actions can be aggregated into a linear approach, where there is a single path of organic matter degradation and multiple conditions must be satisfied in order for methanogenesis to occur. This concept advances our mechanistic understanding of the processes governing anaerobic GHG flux, which is critical to understanding the impact the release of permafrost C will have on the global C cycle.