Abstract. Permafrost thawing of northern peatlands can cause local collapse of peat plateaus into much wetter thermokarst bogs and fens, dominated by Sphagnum mosses and graminoids, respectively. However, permafrost thaw can also improve landscape drainage and thus lead to regional drying of peatlands. How gradual drying of these thawing permafrost peatlands affects the subsequent microbial production of carbon dioxide (CO₂) and nitrous oxide (N₂O) is uncertain because of landscape heterogeneity in moisture, peat quality, and vegetation. Here, we collected near-surface peat samples (5–20 cm) from Alberta, Canada, across transects representing a thaw gradient from peat plateaus to a fen or bog. We incubated the samples for two weeks at either field moisture conditions or under gradual drying, which reduced moisture by ~80 %. Only the fen sites, which had high moisture and % total N, produced N₂O (0.06−6.7 μg N₂O-N g^-1 dry peat) but were unaffected by the drying treatments. Peat CO₂ production was greatest from the fen and the youngest stage of the thermokarst bog despite having the most water-saturated field conditions, likely reflecting their more labile plant inputs and, thus more decomposable peat. We found that CO₂ respiration was enhanced by drying in relatively wet sites like the fens and young bog but was suppressed by drying in relatively drier peat plateaus. Further, gradual drying increased ¹³C-CO₂ respiration, suggesting a possible shift to more decomposed, older C being lost with peat drying. Our study thus suggests that future peat CO₂ and N₂O production from peatlands will depend on whether peat plateaus thaw into fens or bogs and on their diverging responses of peat respiration to more moisture-limited conditions.

中文翻译：

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永久冻土泥炭的逐渐干燥会减少干燥泥炭高原的二氧化碳，但不会减少湿润的沼泽和沼泽


摘要。北部泥炭地的永久冻土融化会导致泥炭高原局部塌陷，形成更加湿润的热喀斯特沼泽和沼泽，分别以泥炭藓和禾本科植物为主。然而，永久冻土融化也会改善景观排水，从而导致泥炭地的区域干燥。由于水分、泥炭质量和植被的景观异质性，这些融化的永久冻土泥炭地的逐渐干燥如何影响随后微生物产生的二氧化碳 (CO ₂ ) 和一氧化二氮 (N ₂ O) 尚不确定。在这里，我们从加拿大阿尔伯塔省收集了近地表泥炭样本（5-20​​ 厘米），跨越代表从泥炭高原到沼泽或沼泽的解冻梯度的横断面。我们将样品在田间湿度条件下或逐渐干燥的条件下孵育两周，从而将湿度降低约 80%。只有具有高水分和％总氮的沼泽地产生N ₂ O（0.06−6.7 μg N ₂ ON g ^-1干泥炭），但不受干燥处理的影响。沼泽地和热喀斯特沼泽的最年轻阶段的泥炭CO ₂产量最高，尽管其田间条件水饱和度最高，这可能反映了植物输入更不稳定，因此泥炭更容易分解。我们发现，在沼泽和年轻沼泽等相对湿润的地区，CO ₂呼吸作用因干燥而增强，但在相对干燥的泥炭高原，则因干燥而受到抑制。此外，逐渐干燥增加了¹³ C-CO ₂呼吸作用，这表明泥炭干燥可能会转变为更分解、更古老的C。 因此，我们的研究表明，泥炭地未来泥炭CO ₂和N ₂ O 的产生将取决于泥炭高原是否解冻成沼泽或沼泽，以及泥炭呼吸对湿度更受限的条件的不同反应。