Despite the presence of well-documented changes in vegetation and faunal communities at the Pleistocene-Holocene transition, it is unclear whether similar shifts occurred in soil microbes. Recent studies do not show a clear connection between soil parameters and community structure, suggesting permafrost microbiome-climate studies may be unreliable. However, the majority of the permafrost microbial ecological studies have been performed only in either Holocene- or Pleistocene-aged sediments and not on permafrost that formed across the dramatic ecosystem reorganization at the Pleistocene-Holocene transition. In our study, we used permafrost recovered in proximity to the Pleistocene-Holocene transition subsampled under strict sterile conditions developed for ancient DNA studies. Our ordination analyses of microbial community composition based on 16S RNA genes and chemical composition of the soil samples resulted into two distinct clusters based on whether they were of late Pleistocene or Holocene age, while samples within an epoch were more similar than those across the boundary and did not result in age based separation. Between epochs, there was a statistically significant correlation between changes in OTU composition and soil chemical properties, but only Ca and Mn were correlated to OTU composition within Holocene aged samples; furthermore, no chemical parameters were correlated to OTU composition within Pleistocene aged samples. Thus, the results indicate that both soil chemical and microbial parameters are fairly stable until a threshold, driven by climate change in our study, is crossed, after which there is a shift to a new steady state. Modern anthropogenic climate change may lead to similar transitions in state for soil biogeochemical systems and microbial communities in Arctic regions.

中文翻译：

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更新世-全新世边界的永久冻土微生物群落结构变化

尽管在更新世-全新世过渡时期植被和动物群落中存在有据可查的变化，但尚不清楚土壤微生物中是否发生了类似的变化。最近的研究没有显示土壤参数和群落结构之间存在明确的联系，这表明多年冻土微生物组气候研究可能不可靠。然而，大多数永久冻土微生物生态学研究仅在全新世或更新世时代的沉积物中进行，而不是在更新世 - 全新世过渡时期戏剧性生态系统重组形成的永久冻土上进行。在我们的研究中，我们使用了在为古代 DNA 研究开发的严格无菌条件下对更新世 - 全新世过渡进行二次采样的永久冻土。我们根据土壤样品的 16S RNA 基因和化学成分对微生物群落组成进行排序分析，根据它们是更新世晚期还是全新世时代，得出两个不同的聚类，而一个时期内的样品比跨越边界的样品更相似，没有导致基于年龄的分离。在不同时期之间，OTU 组成的变化与土壤化学性质之间存在统计学上显着的相关性，但在全新世老化样品中，只有 Ca 和 Mn 与 OTU 组成相关；此外，没有化学参数与更新世老化样品中的 OTU 组成相关。因此，结果表明土壤化学和微生物参数都相当稳定，直到超过我们研究中由气候变化驱动的阈值，之后会转变为新的稳定状态。现代人为气候变化可能导致北极地区土壤生物地球化学系统和微生物群落的类似状态转变。