Abstract
BackgroundSoil 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.ResultsProteobacteria (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.ConclusionsOur 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.
Highlights
Permafrost is soil that remains continuously frozen for at least two years and underlies about 25% of terrestrial area in the Northern Hemisphere (Doherty et al 2020)
Our results suggested that nutrient contents of total carbon content (TC), total nitrogen content (TN) and total phosphorus content (TP) had the greatest influence on both soil microbial community compositions (Fig. 6) and diversity patterns (Table 2) in the permafrost region of northeastern China
This study provides a comprehensive comparison of patterns and drivers of bacterial communities among different soil layers in the continuous permafrost region of northeastern China
Summary
Permafrost is soil that remains continuously frozen for at least two years and underlies about 25% of terrestrial area in the Northern Hemisphere (Doherty et al 2020). Ren et al Ecological Processes (2022) 11:6 widespread permafrost thawing, which has induced a significant reduction of soil organic matter and the subsequent release of greenhouse gases (primarily carbon dioxide (CO2) and methane (CH4)) because of increased microbial activity, and potentially generate positive feedback to climate warming (Mackelprang et al 2011; Graham et al 2012; Heslop et al 2019). A better understanding of the changes in microbial communities in different soil layers and the factors that shape these communities is important to predict the potential microbial processes and permafrost ecosystem functions in a changing climate. 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
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