The Effects of pH, Temperature, and Humic-Like Substances on Anaerobic Carbon Degradation and Methanogenesis in Ombrotrophic and Minerotrophic Alaskan Peatlands
The Effects of pH, Temperature, and Humic-Like Substances on Anaerobic Carbon Degradation and Methanogenesis in Ombrotrophic and Minerotrophic Alaskan Peatlands
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DOI：
10.1007/s10498-020-09372-0
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发表时间：
2020-04
影响因子：
1.6
通讯作者：
Lin Zhang;Xiao Liu;K. Duddleston;M. Hines
中科院分区：
文献类型：
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作者：
Lin Zhang;Xiao Liu;K. Duddleston;M. Hines
甲烷产量通常从酸性泥炭为主的营养型泥炭地向pH偏中性、维管植物盖度较高的营养型泥炭地增加。沿着这个营养型-微营养型梯度，孔隙水中的pH值、微生物群落和溶解有机物的性质都有很大的变化。永久冻土融化和预估的全球变暖导致的水文变化可能通过孔隙水将微营养化和全营养化地点连接起来，并将酸性沼泽转变为微营养化沼泽。因此，研究厌氧碳降解过程如何响应由这种水文变化引起的pH、温度、溶解有机质性质和微生物群落等基本因素的变化是非常重要的。本研究于2017年9月在美国阿拉斯加州费尔班克斯选取了一个营养型（pH = 3.9）泥炭地和一个矿营养型泥炭地，进行了为期42天的厌氧实验室培养，研究了pH、温度和孔隙水分别以及其中两种或三种因素共同作用下厌氧碳降解过程的变化，包括初级和次级发酵、产甲烷和产丙酮。结果表明，降低pH可以抑制除初级发酵外的许多厌氧碳降解过程。在营养化部位，pH升高对产甲烷菌群落没有刺激作用，但初始发酵对pH升高的响应优于单纯温度升高。用高芳香性的近营养区孔隙水替代微营养区孔隙水不会抑制甲烷的生成，但可能带来高效的初级发酵剂。丙酮裂解产甲烷、丙酮生成和合胞作用只存在于微营养区，而不存在于营养区。来自微营养点的孔隙水可能会将醋酸分解产甲烷菌和共生菌引入到营养点，但除非pH和温度都升高，否则不会使它们活跃。当多年冻土融化导致地下水连接营养型泥炭地和微营养型泥炭地时，次生发酵菌和产甲烷菌可以被引入酸性泥炭地，并在高温条件下有效地协同降解营养型泥炭地储存的碳。
Methane production usually increases from the acidic sphagnum-dominated ombrotrophic peatlands to minerotrophic ones with more neutral pH and higher coverage of vascular plants. Along this ombrotrophic–minerotrophic gradient, pH, microbial communities, and properties of dissolved organic matter in porewater all vary greatly. The hydrographic change resulted from permafrost thaw and projected global warming can potentially connect the minerotrophic and ombrotrophic sites via porewater and turn acidic bogs to minerotrophic fens. It is thus very important to investigate how the anaerobic carbon degradation processes respond to changes in fundamental factors like pH, temperature, properties of dissolved organic matter, and microbial communities resulted from such hydrographic change. In this study, one ombrotrophic (pH = 3.9) and one minerotrophic peatland site were sampled in Fairbanks, Alaska in Sep 2017 and a 42-day-period anaerobic laboratory incubation was conducted to study the changes in anaerobic carbon degradation processes including primary and secondary fermentation, methanogenesis, and acetogenesis when pH, temperature, and porewater were manipulated individually and a combination of two or three of these factors. The results suggested lowering pH would inhibit many anaerobic carbon degradation processes in the minerotrophic peatland except primary fermentation. Elevating pH in the ombrotrophic site did not stimulate its methanogen community, but primary fermentation responded better with increasing pH than with increasing temperature alone. Replacing the porewater in the minerotrophic site with that from the ombrotrophic site with high aromaticity did not inhibit methanogenesis but potentially brought in highly efficient primary fermenters. Acetoclastic methanogenesis, acetogenesis, and syntrophy only exist in the minerotrophic site but not at the ombrotrophic one. Porewater from the minerotrophic site could potentially introduce acetoclastic methanogens and syntrophs to the ombrotrophic site but would not make them active unless both pH and temperature were increased. When ground water connects ombrotrophic and minerotrophic peatlands due to thawing of permafrost, secondary fermenters and acetoclastic methanogens could be introduced to acidic bogs and cooperate efficiently to degrade the stored carbon in ombrotrophic peatlands especially under elevated temperature conditions.