Organic peat soils occupy relatively little of the global land surface area but store vast amounts of soil carbon in northern latitudes where climate is warming at a rapid pace. Warming may result in strong positive feedbacks of carbon loss and global climate change driven by microbial processes if warming alters the balance between primary productivity and decomposition. To elucidate effects of warming on the microbial communities mediating peat carbon dynamics, we explored the abundance of broad microbial groups and their source of carbon (i.e. old carbon versus more recently fixed photosynthate) using microbial lipid analysis (δ¹³C PLFA) of peat samples under ambient temperatures and before/after initiation of experimental peat warming (+ 2.25, + 4.5, + 6.75, and + 9 °C). This analysis occurred over a profile to 2 m depth in an undrained, ombrotrophic peat bog in northern Minnesota. We found that the total microbial biomass and individual indicator lipid abundances were stratified by depth and strongly correlated to temperature under ambient conditions. However, under experimental warming, statistically significant effects of temperature on the microbial community were sporadic and inconsistent. For example, 3 months after experimental warming the relative abundance of Gram-negative bacterial indicators across depth combined and > 50 cm depth and Gram-positive bacterial indicators at 20–50 cm depth showed significant positive relationships to temperature. At that same timepoint, however, the relative abundance of Actinobacterial indicators across depth showed a significant negative relationship to temperature. After 10 months of experimental warming, the relative abundance of fungal biomarkers was positively related to temperature in all depths combined, and the absolute abundance of anaerobic bacteria declined with increasing temperature in the 20–50 cm depth interval. The lack of observed response in the broader microbial community may suggest that at least initially, microbial community structure with peat depth in these peatlands is driven more by bulk density and soil water content than temperature. Alternatively, the lack of broad microbial community response may simply represent a lag period, with more change to come in the future. The long-term trajectory of microbial response to warming in this ecosystem then could either be direct, after this initial lag time, or indirect through other physical or biogeochemical changes in the peat profile. These initial results provide an important baseline against which to measure long-term microbial community and carbon-cycling responses to warming and elevated CO₂.

有机泥炭土在全球陆地表面积中所占的面积相对较小，但在气候迅速变暖的北纬地区却储存了大量的土壤碳。如果变暖改变了初级生产力和分解之间的平衡，那么变暖可能会导致微生物过程驱动的碳损失和全球气候变化的强烈正反馈。为了阐明变暖对介导泥炭碳动态的微生物群落的影响，我们使用泥炭样品的微生物脂质分析（δ ¹³ C PLFA）探索了广泛微生物群的丰度及其碳来源（即旧碳与最近固定的光合产物）在环境温度下以及实验泥炭变暖开始之前/之后（+ 2.25、+ 4.5、+ 6.75 和 + 9 °C）。这项分析是在明尼苏达州北部一个不排水、厌氧泥炭沼泽的 2 ​​m 深度剖面上进行的。我们发现总微生物生物量和个体指示剂脂质丰度按深度分层，并且与环境条件下的温度密切相关。然而，在实验变暖的情况下，温度对微生物群落的统计显着影响是零星的且不一致的。例如，实验升温后 3 个月，革兰氏阴性细菌指标在深度组合和 > 50 厘米深度的相对丰度以及革兰氏阳性细菌指标在 20-50 厘米深度的相对丰度与温度呈显着正相关。然而，在同一时间点，放线菌指标在不同深度的相对丰度与温度呈显着负相关。经过10个月的实验升温后，真菌生物标志物的相对丰度与所有深度的温度总和呈正相关，并且厌氧细菌的绝对丰度在20-50 cm深度区间随着温度的升高而下降。在更广泛的微生物群落中缺乏观察到的反应可能表明，至少在最初，这些泥炭地中泥炭深度的微生物群落结构更多地是由容重和土壤含水量而不是温度驱动的。或者，缺乏广泛的微生物群落反应可能只是代表了一个滞后期，未来还会出现更多变化。在这个初始滞后时间之后，微生物对该生态系统变暖的长期反应轨迹可能是直接的，也可能是通过泥炭剖面中的其他物理或生物地球化学变化而间接发生的。这些初步结果为衡量长期微生物群落和碳循环对变暖和CO ₂升高的反应提供了重要的基线。