Climate drivers alter nitrogen availability in surface peat and decouple N2 fixation from CH4 oxidation in the Sphagnum moss microbiome
Climate drivers alter nitrogen availability in surface peat and decouple N2 fixation from CH4 oxidation in the Sphagnum moss microbiome
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气候驱动因素改变了表面泥炭的氮可用性，并将泥炭藓微生物组中的N2固定与CH4氧化分离
DOI：
10.1111/gcb.16651
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发表时间：
2023-03
影响因子：
11.6
通讯作者：
Caitlin Petro;Alyssa A. Carrell;R. Wilson;Katherine Duchesneau;Sekou Noble-Kuchera;T. Song;C. Iversen;J. Childs;Geoffrey W. Schwaner;J. Chanton;R. Norby;P. Hanson;J. Glass;D. Weston;J. Kostka
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作者：
Caitlin Petro;Alyssa A. Carrell;R. Wilson;Katherine Duchesneau;Sekou Noble-Kuchera;T. Song;C. Iversen;J. Childs;Geoffrey W. Schwaner;J. Chanton;R. Norby;P. Hanson;J. Glass;D. Weston;J. Kostka
泥炭藓（Sphagnum spp.）是北方泥炭地的关键物种，它们在净初级生产力中占主导地位，并促进厚泥炭沉积物中碳的积累。泥炭藓拥有多种微生物伙伴，包括固氮（固氮）和甲烷氧化（甲烷氧化）类群，它们通过调节碳和氮的转化来支持生态系统功能。在这里，我们研究了明尼苏达州北部（美国）的暗营养泥炭地中泥炭藓植物群（植物 + 微生物群 + 环境）对实验升温梯度（+0°C 至 +9°C）和二氧化碳浓度升高（+500 ppm）的响应。通过跟踪从地下环境到泥炭藓及其相关微生物组的碳（CH4、CO2）和氮（NH4-N）循环的变化，我们发现了变暖和二氧化碳升高对泥炭藓植物生物组产生的一系列级联影响。在环境 CO2 条件下，变暖增加了表层泥炭中植物可利用的 NH4-N，过量的 N 积累在泥炭藓组织中，并且 N2 固定活性降低。二氧化碳浓度升高抵消了变暖的影响，破坏了泥炭和泥炭藓组织中氮的积累。无论是否进行 CO2 处理，孔隙水中的甲烷浓度都会随着变暖而增加，导致 +9°C 环境下泥炭藓内的甲烷氧化活性增加约 10 倍。变暖对固氮营养和甲烷氧化的不同影响导致这些过程在较高的温度下变得脱钩，甲烷引起的固氮速率下降和关键微生物类群的显着损失就证明了这一点。除了泥炭藓微生物组的变化外，我们还观察到+0°C 和+9°C 处理之间泥炭藓的死亡率约为 94%，这可能是由于变暖对氮可用性和维管植物物种竞争的交互影响。总的来说，这些结果凸显了泥炭藓植物群落对气温升高和大气二氧化碳浓度升高的脆弱性，对北方泥炭地的碳和氮循环具有重大影响。
Peat mosses (Sphagnum spp.) are keystone species in boreal peatlands, where they dominate net primary productivity and facilitate the accumulation of carbon in thick peat deposits. Sphagnum mosses harbor a diverse assemblage of microbial partners, including N2‐fixing (diazotrophic) and CH4‐oxidizing (methanotrophic) taxa that support ecosystem function by regulating transformations of carbon and nitrogen. Here, we investigate the response of the Sphagnum phytobiome (plant + constituent microbiome + environment) to a gradient of experimental warming (+0°C to +9°C) and elevated CO2 (+500 ppm) in an ombrotrophic peatland in northern Minnesota (USA). By tracking changes in carbon (CH4, CO2) and nitrogen (NH4‐N) cycling from the belowground environment up to Sphagnum and its associated microbiome, we identified a series of cascading impacts to the Sphagnum phytobiome triggered by warming and elevated CO2. Under ambient CO2, warming increased plant‐available NH4‐N in surface peat, excess N accumulated in Sphagnum tissue, and N2 fixation activity decreased. Elevated CO2 offset the effects of warming, disrupting the accumulation of N in peat and Sphagnum tissue. Methane concentrations in porewater increased with warming irrespective of CO2 treatment, resulting in a ~10× rise in methanotrophic activity within Sphagnum from the +9°C enclosures. Warming's divergent impacts on diazotrophy and methanotrophy caused these processes to become decoupled at warmer temperatures, as evidenced by declining rates of methane‐induced N2 fixation and significant losses of keystone microbial taxa. In addition to changes in the Sphagnum microbiome, we observed ~94% mortality of Sphagnum between the +0°C and +9°C treatments, possibly due to the interactive effects of warming on N‐availability and competition from vascular plant species. Collectively, these results highlight the vulnerability of the Sphagnum phytobiome to rising temperatures and atmospheric CO2 concentrations, with significant implications for carbon and nitrogen cycling in boreal peatlands.