Drying-Rewetting and Flooding Impact Denitrifier Activity Rather than Community Structure in a Moderately Acidic Fen.
Drying-Rewetting and Flooding Impact Denitrifier Activity Rather than Community Structure in a Moderately Acidic Fen.
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DOI：
10.3389/fmicb.2016.00727
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发表时间：
2016
影响因子：
5.2
通讯作者：
Horn MA
中科院分区：
文献类型：
--
作者：
Palmer K;Köpp J;Gebauer G;Horn MA
湿地是温室气体一氧化二氮(N2O)的源或汇。酸性的fen Schlöppnerbrunnen释放反硝化产生的N2O，也能够消耗N2O。据预测，全球变暖将在未来几年导致更多极端天气事件，包括延长干旱时期以及可能导致洪水的暴雨事件。因此，在人工操作实验中，研究了长期干旱和洪涝事件对沼泽湿地反硝化细菌丰度、群落组成和活性的影响。2008年，在3个处理小区上进行了8周的试验降低沼泽地下水位，2009年又提高了5.5个月，同时有3个小区不进行处理作为对照。干旱处理对土壤N2O排放通量影响不大，淹水处理使土壤N2O通量略有增加。在两年的治疗前后都采集了样本。结构基因标记Narg和nosZ被用来评估硝酸盐还原和反硝化菌群落对地下水位操纵的可能变化。检测到的Narg和nosZ的拷贝数基本不受实验干旱和洪涝的影响。NARG和NOSZ的末端限制性片段长度多态性(TRFLP)图谱在实验干旱或实验淹水前后相似，表明沼泽中存在稳定的硝酸盐还原和反硝化细菌群落。然而，Narg和nosZ转录本的某些TRF对实验中的干旱或洪涝做出了反应。在缺氧微宇宙中，在实验洪水开始前和6个月后采集泥炭样品，评估了硝酸盐依赖的Michaelis-Menten动力学。最大反应速度Vmax在处理后高于淹水前，但在同一时间采集的对照样地中没有增加。淹水后处理小区土壤中N2O/N2O+N_2的比值低于对照小区土壤中的N_2O/N_2O+N_2，表明淹水后N2O还原速率的提高可以缓解N_2O的排放。淹水后，所有微观世界的N2O都被消耗到了大气以下的水平。综合数据表明，地下水位控制对酸性沼泽的N2O通量、反硝化细菌丰度和反硝化细菌群落组成的影响很小，而反硝化细菌的活性亚群则随着地下水位的控制而发生变化，这表明功能上多余的亚群占据着沼泽中不同的生态位。
Wetlands represent sources or sinks of the greenhouse gas nitrous oxide (N2O). The acidic fen Schlöppnerbrunnen emits denitrification derived N2O and is also capable of N2O consumption. Global warming is predicted to cause more extreme weather events in future years, including prolonged drought periods as well as heavy rainfall events, which may result in flooding. Thus, the effects of prolonged drought and flooding events on the abundance, community composition, and activity of fen denitrifiers were investigated in manipulation experiments. The water table in the fen was experimentally lowered for 8 weeks in 2008 and raised for 5.5 months in 2009 on three treatment plots, while three plots were left untreated and served as controls. In situ N2O fluxes were rather unaffected by the drought treatment and were marginally increased by the flooding treatment. Samples were taken before and after treatment in both years. The structural gene markers narG and nosZ were used to assess possible changes in the nitrate reducer and denitrifier community in response to water table manipulations. Detected copy numbers of narG and nosZ were essentially unaffected by the experimental drought and flooding. Terminal restriction fragment length polymorphism (TRFLP) patterns of narG and nosZ were similar before and after experimental drought or experimental flooding, indicating a stable nitrate reducer and denitrifier community in the fen. However, certain TRFs of narG and nosZ transcripts responded to experimental drought or flooding. Nitrate-dependent Michaelis-Menten kinetics were assessed in anoxic microcosms with peat samples taken before and 6 months after the onset of experimental flooding. Maximal reaction velocities vmax were higher after than before flooding in samples from treament but not in those from control plots taken at the same time. The ratio of N2O to N2O + N2 was lower in soil from treatment plots after flooding than in soil from control plots, suggesting mitigation of N2O emissions by increased N2O-reduction rates after flooding. N2O was consumed to subatmospheric levels in all microcosms after flooding. The collective data indicate that water table manipulations had only minor effects on in situ N2O fluxes, denitrifier abundance, and denitrifier community composition of the acidic fen, while active subpopulations of denitrifiers changed in response to water table manipulations, suggesting functionally redundant subpopulations occupying distinct ecological niches in the fen.