Mapping substrate use across a permafrost thaw gradient
Mapping substrate use across a permafrost thaw gradient
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绘制永久冻土融化梯度下的基质使用图
DOI：
10.1016/j.soilbio.2022.108809
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发表时间：
2022
影响因子：
9.7
通讯作者：
Crill, Patrick
中科院分区：
文献类型：
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作者：
Fofana, Aminata;Anderson, Darya;McCalley, Carmody K.;Hodgkins, Suzanne;Wilson, Rachel M.;Cronin, Dylan;Raab, Nicole;Torabi, Mohammad;Varner, Ruth K.;Crill, Patrick
北方泥炭地的永久冻土融化可能会对气候变化产生积极的反馈，因为微生物将土壤碳（C）转化为二氧化碳（CO2）或甲烷（CH 4）。虽然微生物组编码的碳处理潜力随着解冻而变化，但对底物利用和气体排放的影响尚不清楚。因此，我们研究了微生物C-循环动力学从一个部分解冻泥炭藓为主的沼泽完全解冻莎草为主的沼泽在Stordalen沼泽（68.35°N，19.05°E），瑞典。我们通过Biolog Ecoplates™分析了C底物利用的多样性和程度，然后在15 °C厌氧条件下通过有针对性地添加（葡萄糖、短链脂肪酸（SCFA）乙酸酯和丁酸酯以及有机酸半乳糖醛酸和对羟基苯甲酸，所有这些都在田间相关浓度下）来测试底物特异性假设。同时，我们表征了微生物组（通过16 S rRNA扩增子测序和定量聚合酶链反应）和C气体排放。基于Biolog Ecoplate™孵育，与沼泽相比，沼泽表现出更高的底物使用多样性和更快的总体底物利用率。向泥炭缩影中添加简单的葡萄糖（类似于阳性对照），如预期的那样促进发酵（反映在富集的发酵罐谱系、其推断的代谢和二氧化碳产生中），但也显示出沼泽中厌氧苯酚降解的潜在启动。此外SCFAs沼泽和沼泽产生的变化最小的谱系和CO2，和适度的抑制CH 4主要在沼泽，归因于抑制。此外，这两种有机酸大大增加了CO2：CH 4的比例在深泥炭，但有不同的个人气体动力学和微生物群的影响。这两种有机酸似乎既作为碳源，又作为微生物抑制剂，半乳糖醛酸也可能在电子转移或接受中发挥作用。总的来说，这些结果支持了地上-地下联系的重要性，特别是泥炭藓的作用。在这些动态变化的系统中提供驱动微生物组组装和C加工的底物和抑制剂。此外，他们强调了一个重要的时间动态：孵化的短时间尺度上的反应（这将反映在现场的过渡条件）不同于那些明显的在较长的尺度上的栖息地过渡，在方式相应的碳气体排放。在短期内，底物添加反应反映了微生物组的遗传（例如，沼泽群落比沼泽群落更慢地处理C和更好地耐受抑制剂），但导致C气体产量的总体增加很少（和对CO2的高偏斜）。在沼泽和沼泽解冻阶段（用于在模型中代表这些系统）的较长时间尺度上，植物、水文和微生物群的伴随变化会随着时间的推移减弱微生物群对基质处理和碳气体排放的影响。随着栖息地过渡区在加速变化下扩大，我们假设微生物组遗产在整体景观中的作用增加，导致沼泽扩张预期的CH 4排放量增加滞后。
Permafrost thaw in northern peatlands is likely to create a positive feedback to climate change, as microbes transform soil carbon (C) into carbon dioxide (CO2) or methane (CH4). While the microbiome's encoded C-processing potential changes with thaw, the impact on substrate utilization and gas emissions is less well characterized. We therefore examined microbial C-cycling dynamics from a partially thawedSphagnum-dominated bog to a fully thawed sedge-dominated fen in Stordalen Mire (68.35°N, 19.05°E), Sweden. We profiled C substrate utilization diversity and extent by Biolog Ecoplates™, then tested substrate-specific hypotheses by targeted additions (of glucose, the short chain fatty acids (SCFAs) acetate and butyrate, and the organic acids galacturonic acid and p-hydroxybenzoic acid, all at field-relevant concentrations) under anaerobic conditions at 15 °C. In parallel we characterized microbiomes (via 16S rRNA amplicon sequencing and quantitative polymerase chain reaction) and C gas emissions. The fen exhibited a higher substrate use diversity and faster rate of overall substrate utilization than in the bog, based on Biolog Ecoplate™ incubations. Simple glucose additions (akin to a positive control) to peat microcosms fueled fermentation as expected (reflected in enriched fermenter lineages, their inferred metabolisms, and CO2production), but also showed potential priming of anaerobic phenol degradation in the bog. Addition of SCFAs to bog and fen produced the least change in lineages and in CO2, and modest suppression of CH4primarily in the fen, attributed to inhibition. Addition of both organic acids greatly increased the CO2:CH4ratio in the deep peats but had distinct individual gas dynamics and impacts on microbiota. Both organic acids appeared to act as both C source and as a microbial inhibitor, with galacturonic acid also likely playing a role in electron transfer or acceptance. Collectively, these results support the importance of aboveground-belowground linkages - and in particular the role ofSphagnumspp.- in supplying substrates and inhibitors that drive microbiome assembly and C processing in these dynamically changing systems. In addition, they highlight an important temporal dynamic: responses on the short time scale of incubations (which would reflect transition conditions in the field) differ from those evident at the longer scales of habitat transition, in ways consequential to C gas emissions. In the short term, substrate addition response reflected microbiome legacy (e.g., bog communities were slower to process C and better tolerated inhibitors than fen communities) but led to little overall increase in C gas production (and a high skew to CO2). At the longer time scale of bog and fen thaw stages (which are used to represent these systems in models) the concomitant shifts in plants, hydrology and microbiota attenuate microbiome legacy impacts on substrate processing and C gas emissions over time. As habitat transition areas expand under accelerating change, we hypothesize an increased role of microbiome legacy in the landscape overall, leading to a lag in the increase of CH4emissions expected from fen expansion.