Department of Biogeochemistry, Max Planck Institute of Terrestrial Microbiology, Marburg, Germany.
Glob Chang Biol. 2017 Nov;23(11):4884-4895. doi: 10.1111/gcb.13764. Epub 2017 Jun 14.
Data from remote sensing and Eddy towers indicate that forests are not always net sinks for atmospheric CH . However, studies describing specific sources within forests and functional analysis of microorganisms on sites with CH turnover are scarce. Feather moss stands were considered to be net sinks for carbon dioxide, but received little attention to their role in CH cycling. Therefore, we investigated methanogenic rates and pathways together with the methanogenic microbial community composition in feather moss stands from temperate and boreal forests. Potential rates of CH emission from intact moss stands (n = 60) under aerobic conditions ranged between 19 and 133 pmol CH h gdw . Temperature and water content positively influenced CH emission. Methanogenic potentials determined under N atmosphere in darkness ranged between 22 and 157 pmol CH h gdw . Methane production was strongly inhibited by bromoethane sulfonate or chloroform, showing that CH was of microbial origin. The moss samples tested contained fluorescent microbial cells and between 10 and 10 copies per gram dry weight moss of the mcrA gene coding for a subunit of the methyl CoM reductase. Archaeal 16S rRNA and mcrA gene sequences in the moss stands were characteristic for the archaeal families Methanobacteriaceae and Methanosarcinaceae. The potential methanogenic rates were similar in incubations with and without methyl fluoride, indicating that the CH was produced by the hydrogenotrophic rather than aceticlastic pathway. Consistently, the CH produced was depleted in C in comparison with the moss biomass carbon and acetate accumulated to rather high concentrations (3-62 mM). The δ C of acetate was similar to that of the moss biomass, indicating acetate production by fermentation. Our study showed that the feather moss stands contained active methanogenic microbial communities producing CH by hydrogenotrophic methanogenesis and causing net emission of CH under ambient conditions, albeit at low rates.
遥感和涡度塔的数据表明，森林并不总是大气 CH 的净汇。然而，描述森林内特定源和具有 CH 转化功能的微生物的研究很少。羽毛藓被认为是二氧化碳的净汇，但它们在 CH 循环中的作用却很少受到关注。因此，我们研究了来自温带和北方森林的羽毛藓中甲烷生成速率和途径以及甲烷生成微生物群落组成。在有氧条件下，完整苔藓植物的潜在 CH 排放速率（n = 60）在 19 到 133 pmol CH h gdw 之间。温度和水分含量对 CH 排放有积极影响。在黑暗中氮气气氛下测定的甲烷生成潜力在 22 到 157 pmol CH h gdw 之间。溴乙磺酸钠或三氯甲烷强烈抑制甲烷生成，表明 CH 源自微生物。测试的苔藓样本含有荧光微生物细胞，并且每克干重苔藓中含有 10 到 10 个拷贝的编码甲基 CoM 还原酶亚基的 mcrA 基因。苔藓植物中的古菌 16S rRNA 和 mcrA 基因序列特征为甲烷杆菌科和甲烷八叠球菌科。在有和没有甲基氟化物的孵育中，潜在的甲烷生成速率相似，表明 CH 是由氢营养型而不是乙酸营养型途径生成的。一致地，与苔藓生物质相比，生成的 CH 中 13C 被耗尽，并且乙酸积累到相当高的浓度（3-62 mM）。乙酸的 δ 13C 与苔藓生物质的相似，表明乙酸通过发酵产生。我们的研究表明，羽毛藓植物中含有活跃的甲烷生成微生物群落，通过氢营养型甲烷生成产生 CH，并在环境条件下导致 CH 的净排放，尽管排放速率很低。
