How does elevated ozone reduce methane emissions from peatlands?
How does elevated ozone reduce methane emissions from peatlands?
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DOI：
10.1016/j.scitotenv.2016.10.188
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
S. Toet;V. Oliver;P. Ineson;Sophie McLoughlin;T. Helgason;S. Peacock;A. Stott;J. Barnes;M. Ashmore
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文献类型：
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作者：
S. Toet;V. Oliver;P. Ineson;Sophie McLoughlin;T. Helgason;S. Peacock;A. Stott;J. Barnes;M. Ashmore
对流层臭氧（O3）污染水平增加对泥炭地甲烷（CH 4）排放的影响及其潜在机制尚不清楚。在这项研究中，我们暴露泥炭地的中型生态系统从温带潮湿的石南为主的莎草Schoenus nigricans和泥炭藓乳头状，以4个O3处理在开顶的商会为2.5年，调查O3对CH 4排放的影响和过程，这些反应的基础。由于夏季白天（8小时天-1）O3暴露于未过滤空气（NFA）加35 ppb O3，夏季CH 4排放量在实验中显着减少了27%，但全年24小时天-1暴露于NFA加10 ppb或NFA加25 ppb O3并未受到显着影响。没有证据表明，减少CH 4排放量，以应对夏季O3暴露升高是由减少植物来源的地下碳的可用性，因为我们发现没有显着影响的高夏季O3暴露对根生物量，孔隙水溶解的有机碳浓度或最近的光合作用的贡献CH 4排放。我们的CH 4生产潜力和CH 4氧化电位测量在不同的O3处理也不能解释所观察到的CH 4排放响应O3。然而，在20厘米深的孔隙水铵浓度不断减少，在实验期间，夏季O3暴露升高，和强烈的正相关关系，观察到CH 4排放和孔隙水铵浓度在三个泥炭深度超过2.5年的研究。因此，我们的研究结果意味着，在夏季升高区域O3暴露，但不是小的增加，在北方半球的年平均背景O3浓度预测在本世纪，可能会导致减少CH 4排放量从温带泥炭地的土壤无机氮影响产甲烷和/或甲烷氧化活性的减少的结果。
The effects of increased tropospheric ozone (O3) pollution levels on methane (CH4) emissions from peatlands, and their underlying mechanisms, remain unclear. In this study, we exposed peatland mesocosms from a temperate wet heath dominated by the sedgeSchoenus nigricansandSphagnum papillosumto four O3treatments in open-top chambers for 2.5 years, to investigate the O3impacts on CH4emissions and the processes that underpin these responses. Summer CH4emissions, were significantly reduced, by 27% over the experiment, due to summer daytime (8 h day− 1) O3exposure to non-filtered air (NFA) plus 35 ppb O3, but were not significantly affected by year-round, 24 h day− 1, exposure to NFA plus 10 ppb or NFA plus 25 ppb O3. There was no evidence that the reduced CH4emissions in response to elevated summer O3exposure were caused by reduced plant-derived carbon availability below-ground, because we found no significant effect of high summer O3exposure on root biomass, pore water dissolved organic carbon concentrations or the contribution of recent photosynthate to CH4emissions. Our CH4production potential and CH4oxidation potential measurements in the different O3treatments could also not explain the observed CH4emission responses to O3. However, pore water ammonium concentrations at 20 cm depth were consistently reduced during the experiment by elevated summer O3exposure, and strong positive correlations were observed between CH4emission and pore water ammonium concentration at three peat depths over the 2.5-year study. Our results therefore imply that elevated regional O3exposures in summer, but not the small increases in northern hemisphere annual mean background O3concentrations predicted over this century, may lead to reduced CH4emissions from temperate peatlands as a consequence of reductions in soil inorganic nitrogen affecting methanogenic and/or methanotrophic activity.