Effect of water-table fluctuations on the degradation of Sphagnum phenols in surficial peats
Effect of water-table fluctuations on the degradation of Sphagnum phenols in surficial peats
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DOI：
10.1016/j.gca.2012.12.013
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发表时间：
2013-04
影响因子：
5
通讯作者：
G. Abbott;E. Swain;A. Muhammad;K. Allton;L. R. Belyea;C. Laing;G. Cowie
中科院分区：
文献类型：
--
作者：
G. Abbott;E. Swain;A. Muhammad;K. Allton;L. R. Belyea;C. Laing;G. Cowie
为了预测泥炭地碳循环和全球气候系统之间可能的反馈，需要更好地了解地表附近的地下水位波动如何影响泥炭形成的植物凋落物和表层泥炭的分解和保存。在这项研究中，泥炭地植物（brabrites和维管植物），他们的凋落物和泥炭核心收集的Ryggmossen泥炭地在boreonemoral区瑞典中部。从整个植物组织提取的不溶性残留物解聚使用热辅助水解和甲基化（THM）在未标记和13 C-标记的四甲基氢氧化铵（TMAH）的存在下，产生维管植物和泥炭藓衍生的酚。甲基化的4-异丙烯基苯酚（IUPAC：1-甲氧基-4-（丙-1-烯-2-基）苯）、甲基化的顺式-和反式-3-（4′-羟基苯-1-基）丁-2-烯酸（IUPAC：（E/Z）-甲基3-（4-甲氧基苯基）丁-2-烯酸酯）和甲基化的3-（4′-羟基苯-1-基）丁-3-烯酸（IUPAC：甲基3-（4-甲氧基苯基）丁-3-烯酸酯）（货车der Heijden等人，1997）被确认为“结合的”泥炭藓酸的TMAH热化学分解产物，并且也被确认为对泥炭藓属藓类具有特异性。这些推定的生物标志物也是显着的成分，在未标记的TMAH热化学分解产物从超声波提取的样品从八个泥炭芯，一个从一个小丘和一个从一个空心的四个阶段沿着沼泽高原沼泽森林梯度的解聚。我们提出并测量了两个参数，即（i）σ，定义为归一化为100 mg OC的这四种分子的总量;和（ii）一个指数（SR%），是σ与Λ参数的比值，给出了泥炭藓和表层泥炭层中“结合”泥炭藓酸与“结合”维管植物酚的相对量的度量。Ryggmossen沼泽中沼泽高原（BP）、沼泽边缘（BM）和沼泽（FL）岩芯的σ和SR%的变化表明，结合到泥炭中的泥炭藓酸在非饱和层和季节性饱和层中正在降解。然后，在季节性饱和层的最深层和永久饱和层中，泥炭藓衍生的酚类稳定。这些结果表明，“结合”泥炭藓酸将稳定在泥炭地转移到一个更潮湿和更多变的降水制度，而它将逐渐剥离（例如，通过水解/酶活性），在surgical泥炭转移到一个干燥的气候，使任何随后的重新湿润的泥炭可能会导致厌氧水解和发酵的新暴露的碳水化合物。这突出了泥炭藓泥炭对气候引起的水位变化的敏感性，尽管沿沿着沼泽梯度的退化程度可能存在差异。
A much improved understanding of how water-table fluctuations near the surface affect decomposition and preservation of peat-forming plant litter and surficial peats is needed in order to predict possible feedbacks between the peatland carbon cycle and the global climate system. In this study peatland plants (bryophytes and vascular plants), their litter and peat cores were collected from the Ryggmossen peatland in the boreonemoral zone of central Sweden. The extracted insoluble residues from whole plant tissues were depolymerized using thermally assisted hydrolysis and methylation (THM) in the presence of both unlabelled and13C-labelled tetramethylammonium hydroxide (TMAH) which yielded both vascular plant- and Sphagnum-derived phenols. Methylated 4-isopropenylphenol (IUPAC: 1-methoxy-4-(prop-1-en-2-yl)benzene), methylated cis- and trans-3-(4′-hydroxyphen-1-yl)but-2-enoic acid (IUPAC: (E/Z)-methyl 3-(4-methoxyphenyl)but-2-enoate), and methylated 3-(4′-hydroxyphen-1-yl)but-3-enoic acid (IUPAC: methyl 3-(4-methoxyphenyl)but-3-enoate) (van der Heijden et al., 1997) are confirmed as TMAH thermochemolysis products of “bound” sphagnum acid and also as being specific to Sphagnum mosses. These putative biomarkers were also significant components in the unlabelled TMAH thermochemolysis products from the depolymerization of ultrasonically extracted samples from eight peat cores, one from a hummock and one from a hollow at each of the four stages along the bog plateau-to-swamp forest gradient. We have proposed and measured two parameters namely (i) σ which is defined as the total amount of these four molecules normalised to 100mg of OC; and (ii) an index (SR%) which is the ratio of σ to the Λ parameter giving a measure of the relative amounts of “bound” sphagnum acid to the “bound” vascular plant phenols in peat moss and the surficial peat layers. Changes in σ and SR% down the bog plateau (BP), bog margin (BM) and fen lagg (FL) cores in the Ryggmossen mire indicates that the sphagnum acid bound into the peat is being degraded in the unsaturated and seasonally-saturated layers. There is then a stabilisation of Sphagnum-derived phenols in the deepest horizons of the seasonally-saturated layer and into the permanently-saturated layer. These results suggest that “bound” sphagnum acid will be stabilised in peatlands shifting to a wetter and more variable precipitation regime whereas it will be gradually stripped away (e.g. by hydrolysis/enzymatic activity) in surficial peats shifting to a drier climate, such that any subsequent rewetting of the peat could lead to anaerobic hydrolysis and fermentation of the newly exposed carbohydrates. This highlights the sensitivity of Sphagnum surficial peats to climate-induced changes in water levels albeit there may be differences in the extent of degradation along the bog-fen gradient.