Zhang Hui, Tuittila Eeva-Stiina, Korrensalo Aino, Laine Anna M, Uljas Salli, Welti Nina, Kerttula Johanna, Maljanen Marja, Elliott David, Vesala Timo, Lohila Annalea
Institute for Atmospheric and Earth System Research (INAR), Department of Physics, University of Helsinki, Helsinki, Finland.
Helsinki Institute of Sustainability Science (HELSUS), Helsinki, Finland.
Glob Chang Biol. 2021 Sep;27(18):4449-4464. doi: 10.1111/gcb.15740. Epub 2021 Jun 28.
Methane (CH ) emissions from northern peatlands are projected to increase due to climate change, primarily because of projected increases in soil temperature. Yet, the rates and temperature responses of the two CH emission-related microbial processes (CH production by methanogens and oxidation by methanotrophs) are poorly known. Further, peatland sites within a fen-bog gradient are known to differ in the variables that regulate these two mechanisms, yet the interaction between peatland type and temperature lacks quantitative understanding. Here, we investigated potential CH production and oxidation rates for 14 peatlands in Finland located between c. 60 and 70°N latitude, representing bogs, poor fens, and rich fens. Potentials were measured at three different temperatures (5, 17.5, and 30℃) using the laboratory incubation method. We linked CH production and oxidation patterns to their methanogen and methanotroph abundance, peat properties, and plant functional types. We found that the rich fen-bog gradient-related nutrient availability and methanogen abundance increased the temperature response of CH production, with rich fens exhibiting the greatest production potentials. Oxidation potential showed a steeper temperature response than production, which was explained by aerenchymous plant cover, peat water holding capacity, peat nitrogen, and sulfate content. The steeper temperature response of oxidation suggests that, at higher temperatures, CH oxidation might balance increased CH production. Predicting net CH fluxes as an outcome of the two mechanisms is complicated due to their different controls and temperature responses. The lack of correlation between field CH fluxes and production/oxidation potentials, and the positive correlation with aerenchymous plants points toward the essential role of CH transport for emissions. The scenario of drying peatlands under climate change, which is likely to promote Sphagnum establishment over brown mosses in many places, will potentially reduce the predicted warming-related increase in CH emissions by shifting rich fens to Sphagnum-dominated systems.
预计气候变化将导致北半球泥炭地的甲烷（CH₄）排放量增加，主要原因是土壤温度预计会上升。然而，与CH₄排放相关的两个微生物过程（产甲烷菌产生CH₄和甲烷氧化菌进行氧化）的速率和温度响应尚不清楚。此外，已知在富营养化沼泽-泥炭藓沼泽梯度内的泥炭地在调节这两种机制的变量方面存在差异，但泥炭地类型与温度之间的相互作用缺乏定量认识。在此，我们调查了芬兰14个位于北纬约60°至70°之间的泥炭地的潜在CH₄产生和氧化速率，这些泥炭地代表了泥炭藓沼泽、贫营养化沼泽和富营养化沼泽。使用实验室培养方法在三种不同温度（5℃、17.5℃和30℃）下测量了潜力。我们将CH₄产生和氧化模式与其产甲烷菌和甲烷氧化菌丰度、泥炭性质以及植物功能类型联系起来。我们发现，与富营养化沼泽-泥炭藓沼泽梯度相关的养分可用性和产甲烷菌丰度增加了CH₄产生的温度响应，富营养化沼泽表现出最大的产生潜力。氧化潜力比产生表现出更陡峭的温度响应，这可以通过通气组织植物覆盖、泥炭持水能力、泥炭氮和硫酸盐含量来解释。氧化更陡峭的温度响应表明，在较高温度下，CH₄氧化可能会平衡增加的CH₄产生。由于这两种机制的控制和温度响应不同，将净CH₄通量预测为这两种机制的结果很复杂。实地CH₄通量与产生/氧化潜力之间缺乏相关性，以及与通气组织植物的正相关表明CH₄传输对排放起着至关重要的作用。气候变化下泥炭地干涸的情景可能会在许多地方促进泥炭藓在棕色苔藓上的生长，通过将富营养化沼泽转变为以泥炭藓为主的系统，有可能减少预测的与变暖相关的CH₄排放增加。
