Permafrost thaw in northern peatlands alters the ground thermal conditions, moisture, and chemistry that control microbial activity responsible for the production of greenhouse gases (GHGs) like methane from decomposing organic matter. This paper examines interactions between microbial communities, peat chemistry, moisture content, and temperature in the context of degrading palsa fields in the vast (372,000 km²), carbon rich, and rapidly warming permafrost peatlands of the Hudson Bay Lowlands. The temperature sensitivities of microbial GHG production and consumption from palsa and fen peat were assessed, and microbial community structure was examined as a potential constraint on GHG production in relation to changes in peat chemistry associated with thermokarst encroachment and active layer deepening. High CH₄ production was observed from thermokarst peat, under controlled moisture and temperature conditions, associated with increased pH. A shift in methanogen taxonomic and metabolic diversity favoring aceticlastic methanogenesis was associated with changes in peat chemistry and pH from palsa to thermokarst fen peat. In palsa peat, CH₄ production rates were lowest but most sensitive to temperature variations, due to recalcitrant carbon compounds. CH₄ production was highly sensitive to increased temperatures, yet was balanced by high temperature sensitivity of CH₄ oxidation in oxic conditions, consistent with the low temperature sensitivity of fluxes observed in field studies from other permafrost peatlands. Building on the microbial controls in this study, future work should explore how permafrost degradation and increased hydrological connectivity to mineral substrates are changing in this globally significant permafrost peatland, and how this impacts net CH₄ emissions.

中文翻译：

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哈德逊湾低地 Palsa 田地土壤微生物群落对多年冻土退化的响应：对气候变暖中温室气体生产的影响

北部泥炭地的永久冻土融化改变了控制微生物活动的地热条件、水分和化学物质，这些微生物活动负责产生温室气体 (GHG)，如有机物分解产生的甲烷。本文研究了在哈德逊湾低地广袤（372,000 公里²）、富含碳和快速变暖的永久冻土泥炭地退化的帕萨田中，微生物群落、泥炭化学、水分含量和温度之间的相互作用。评估了来自 palsa 和 fen 泥炭的微生物 GHG 生产和消耗的温度敏感性，并检查了微生物群落结构作为与热岩溶侵蚀和活动层加深相关的泥炭化学变化相关的 GHG 生产的潜在约束。高 CH₄从热岩溶泥炭中观察到，在受控的水分和温度条件下，与增加的 pH 值相关。产甲烷菌分类学和代谢多样性的转变有利于醋酸产甲烷生成与泥炭化学和 pH 值的变化有关，从 palsa 到热岩溶泥炭。在 palsa 泥炭中，由于顽固的碳化合物，CH ₄生产率最低，但对温度变化最敏感。CH ₄生产对升高的温度高度敏感，但被 CH _{4 的}高温敏感性平衡氧化条件下的氧化，与在其他永久冻土泥炭地的实地研究中观察到的通量的低温敏感性一致。在本研究中微生物控制的基础上，未来的工作应该探索在这个具有全球意义的永久冻土泥炭地中，永久冻土退化和与矿物基质增加的水文连通性如何发生变化，以及这如何影响净 CH ₄排放。