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 micro-bial 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.
东北地区是我国沼泽湿地分布最广泛的地区。为研究沼泽湿地对气候变化的响应,选取了对沼泽湿地分布可能存在影响的26个环境因子,利用最大熵(Maximum Entropy,MaxEnt)模型模拟了沼泽湿地基准气候条件下的潜在分布,并预测了气候变化情景下2011—2040年、2041—2070年和2071—2100年3个研究阶段东北沼泽湿地潜在分布。研究结果表明:最大熵模型预测精度较高(平均AUC(Aera Under Curve)为(0.826±0.005))。基准气候条件下东北沼泽潜在分布区主要为大小兴安岭和三江平原地区。随着时间的推进,东北地区沼泽湿地原有潜在分布面积明显减少,而新增潜在分布面积较少,总面积呈现急剧减少趋势。至2071—2100年,原有沼泽湿地潜在分布面积将减少99.80%,新增潜在分布面积仅2.48%,总潜在分布面积减少97.32%。空间分布上,东北沼泽湿地潜在分布呈现由东向西迁移,南北向中心收缩的趋势。研究结果可为东北地区沼泽湿地保护政策的制定提供参考。
