Chiri Eleonora, Nauer Philipp A, Rainer Edda-Marie, Zeyer Josef, Schroth Martin H
Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zurich, Zurich, Switzerland.
Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zurich, Zurich, Switzerland
Appl Environ Microbiol. 2017 Aug 31;83(18). doi: 10.1128/AEM.01139-17. Print 2017 Sep 15.
Glacier forefield soils can provide a substantial sink for atmospheric CH, facilitated by aerobic methane-oxidizing bacteria (MOB). However, MOB activity, abundance, and community structure may be affected by soil age, MOB location in different forefield landforms, and temporal fluctuations in soil physical parameters. We assessed the spatial and temporal variability of atmospheric-CH oxidation in an Alpine glacier forefield during the snow-free season of 2013. We quantified CH flux in soils of increasing age and in different landforms (sandhill, terrace, and floodplain forms) by using soil gas profile and static flux chamber methods. To determine MOB abundance and community structure, we employed gene-based quantitative PCR and targeted amplicon sequencing. Uptake of CH increased in magnitude and decreased in variability with increasing soil age. Sandhill soils exhibited CH uptake rates ranging from -3.7 to -0.03 mg CH m day Floodplain and terrace soils exhibited lower uptake rates and even intermittent CH emissions. Linear mixed-effects models indicated that soil age and landform were the dominating factors shaping CH flux, followed by cumulative rainfall (weighted sum ≤4 days prior to sampling). Of 31 MOB operational taxonomic units retrieved, ∼30% were potentially novel, and ∼50% were affiliated with upland soil clusters gamma and alpha. The MOB community structures in floodplain and terrace soils were nearly identical but differed significantly from the highly variable sandhill soil communities. We concluded that soil age and landform modulate the soil CH sink strength in glacier forefields and that recent rainfall affects its short-term variability. This should be taken into account when including this environment in future CH inventories. Oxidation of methane (CH) in well-drained, "upland" soils is an important mechanism for the removal of this potent greenhouse gas from the atmosphere. It is largely mediated by aerobic, methane-oxidizing bacteria (MOB). Whereas there is abundant information on atmospheric-CH oxidation in mature upland soils, little is known about this important function in young, developing soils, such as those found in glacier forefields, where new sediments are continuously exposed to the atmosphere as a result of glacial retreat. In this field-based study, we investigated the spatial and temporal variability of atmospheric-CH oxidation and associated MOB communities in Alpine glacier forefield soils, aiming at better understanding the factors that shape the sink for atmospheric CH in this young soil ecosystem. This study contributes to the knowledge on the dynamics of atmospheric-CH oxidation in developing upland soils and represents a further step toward the inclusion of Alpine glacier forefield soils in global CH inventories.
在好氧甲烷氧化细菌（MOB）的作用下，冰川前缘土壤能够成为大气中甲烷的重要汇。然而，MOB的活性、丰度和群落结构可能会受到土壤年龄、MOB在不同前缘地貌中的位置以及土壤物理参数的时间波动的影响。我们评估了2013年无雪季节阿尔卑斯山冰川前缘大气甲烷氧化的时空变异性。我们通过土壤气体剖面和静态通量箱方法，对年龄不断增加的土壤以及不同地貌（沙丘、阶地和洪泛平原）中的甲烷通量进行了量化。为了确定MOB的丰度和群落结构，我们采用了基于基因的定量PCR和靶向扩增子测序技术。随着土壤年龄的增加，甲烷的吸收量增加，变异性降低。沙丘土壤的甲烷吸收率在-3.7至-0.03毫克甲烷/平方米·天之间。洪泛平原和阶地土壤的吸收率较低，甚至会间歇性地排放甲烷。线性混合效应模型表明，土壤年龄和地貌是影响甲烷通量的主要因素，其次是累积降雨量（采样前≤4天的加权总和）。在检索到的31个MOB操作分类单元中，约30%可能是新物种，约50%与高地土壤簇γ和α相关。洪泛平原和阶地土壤中的MOB群落结构几乎相同，但与高度可变的沙丘土壤群落有显著差异。我们得出结论，土壤年龄和地貌调节着冰川前缘土壤中大气甲烷汇的强度，近期降雨影响其短期变异性。在将这种环境纳入未来的甲烷清单时应考虑到这一点。在排水良好的“高地”土壤中，甲烷（CH）的氧化是从大气中去除这种强效温室气体的重要机制。这主要由好氧甲烷氧化细菌（MOB）介导。虽然关于成熟高地土壤中大气甲烷氧化有丰富的信息，但对于年轻的发育中土壤（如冰川前缘发现的土壤，由于冰川退缩，新沉积物不断暴露于大气中）的这一重要功能却知之甚少。在这项基于实地的研究中，我们调查了阿尔卑斯山冰川前缘土壤中大气甲烷氧化及相关MOB群落的时空变异性，旨在更好地了解影响这种年轻土壤生态系统中大气甲烷汇的因素。这项研究有助于了解发育中高地土壤中大气甲烷氧化的动态，并朝着将阿尔卑斯山冰川前缘土壤纳入全球甲烷清单迈出了进一步的一步。
