Plant rhizosphere oxidation reduces methane production and emission in rewetted peatlands
Plant rhizosphere oxidation reduces methane production and emission in rewetted peatlands
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DOI：
10.1016/j.soilbio.2018.07.006
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发表时间：
2018-10-01
影响因子：
9.7
通讯作者：
Knorr, Klaus-Holger
中科院分区：
文献类型：
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作者：
Agethen, Svenja;Sander, Michael;Knorr, Klaus-Holger
由于排水或泥炭开采造成的全球泥炭地流失，鼓励采取措施恢复这些生态系统及其作为碳汇的功能。然而，恢复后的泥炭地有可能排放大量温室气体CH4。维管植物通常在修复地点占据主导地位，在决定甲烷排放量方面发挥着关键作用：这些植物既可以通过提供活性碳来促进甲烷生成，也可以通过将氧气转移到根际来减弱甲烷生成。为了量化这些抵消过程的净影响，我们以双管齐下的方法测试了CH4的产生、排放和(1)中的潜在过程。三种不同采伐后的泥炭地和(2.)中胚层含有绒毛蟹、狭叶艾美耳草和多孔雀，而对照组只有泥炭和泥炭。尽管浸水，因此持续的缺氧条件，溶解的CH4浓度在所有测试的整体中保持接近于零。我们将这一发现归因于两个因素：在缺氧培养中确定的泥炭材料的腐解性很差，以及替代电子受体的可用性，这些电子受体持续了厌氧呼吸并竞争性地抑制了甲烷的产生。虽然无机电子受体池很小且迅速减少，但溶解有机质提供了恒定的电子受体容量，表明所有受试维管植物的根际有机质中的可还原部分都被持续地重新氧化。这种溶解有机物的持续再氧化与植物生长速率相关(R-2=0.6-0.8)，这表明通过植物根的通风组织提供氧气可以再生根际的电子受体能力。维管植物可能对净生态系统交换有不同的影响，然而，我们的发现表明，恢复后的泥炭地可能在几个月到几年的时间里保持较低的CH4浓度和排放量。因此，退化的泥炭砍伐地的内涝和维管植物覆盖并不一定会产生CH4排放的热点。
The global loss of peatlands, by drainage or peat extraction, has encouraged measures to restore these ecosystems and their function as carbon sinks. However, there is a potential of high emissions of the potent greenhouse gas CH4 from restored peatlands. Vascular plants, which often dominate restored sites, play a key role in determining the amount of emitted CH4: The plants can either fuel methanogenesis by supplying labile carbon or attenuate methanogenesis by transferring oxygen into the rhizosphere. To quantify the net effect of these counteracting processes, we tested in a two-pronged approach CH4 production, emission, and the underlying processes in (1.) monoliths of three different restored cutover peatlands and in (2.) mesocosms with Eriophorwn vaginatwn, E. angustifolium and Juncos effusus versus controls with Sphagna and bare peat. Despite waterlogged, and thus persisting anoxic conditions, concentrations of dissolved CH4 remained close to zero in all tested monoliths. We ascribe this finding to two factors: The poor decomposability of the peat material, as determined in anoxic incubations, and the availability of alternative electron acceptors that sustained anaerobic respiration and competitively suppressed methanogenesis. While inorganic electron acceptor pools were small and rapidly diminished, dissolved organic matter provided constant electron acceptor capacity, indicating that reducible moieties in the organic matter were continuously re-oxidized in the rhizosphere of all tested vascular plant species. This continuous re-oxidation of the dissolved organic matter correlated with plant growth rates (R-2 = 0.6-0.8), suggesting that supply of oxygen through the aerenchyma of plant roots regenerated electron acceptor capacity in the rhizosphere. Vascular plants may have differential effects on the net ecosystem exchange, however, our findings suggest that CH4 concentrations and emissions may remain low in restored cutover peatlands for months to years. Thus, waterlogging and vascular plant cover of degraded cutover peat lands does not necessarily create hot-spots of CH4 emissions.