Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin
Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin
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DOI：
10.5194/bg-14-3669-2017
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发表时间：
2017-08
期刊：
影响因子：
4.9
通讯作者：
Yit Arn;J. Berrío
中科院分区：
文献类型：
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作者：
Yit Arn;J. Berrío
抽象的。亚马逊在全球大气中甲烷（CH 4）和一氧化二氮（N2 O）的收支中发挥着关键作用。然而，虽然我们对这些温室气体（GHG）的大陆尺度通量有了相对较好的了解，但知识的主要差距之一是泥炭地生态系统对这些GHG的区域预算的具体贡献。在这里，我们报告的CH 4和N2 O通量从低地热带泥炭地在Pastaza-马拉农前陆盆地（PMFB）在秘鲁，在亚马逊盆地最大的泥炭地复合体之一。本研究的目标是量化的范围和幅度的CH 4和N2 O通量从该地区，评估痕量气体交换的季节性趋势，并确定不同的环境变量在驱动温室气体通量的作用。微量气体通量的测定，从最占主导地位的泥炭地植被类型在该地区：森林植被，森林（短极）植被，棕榈树flexuosa为主的棕榈沼泽，混合棕榈沼泽。在2012年至2014年的四次实地活动中，收集了雨季和旱季的数据。整个数据集的扩散CH 4排放量平均为36.05 ± 3.09 mg CH 4-C m−2 day−1，扩散CH 4通量在植被类型和季节之间变化显著。CH 4的净沸腾平均为973.3 ± 161.4 mg CH 4-C m−2 day−1，在不同植被类型或季节之间没有显著差异。混合棕榈沼泽的CH 4扩散通量最大（52.0 ± 16.0 mg CH 4-Cm −2 day−1），其次是M. flexuosa棕榈沼泽（36.7 ± 3.9 mg CH 4-C m−2 day−1）、森林（短杆）植被（31.6 ± 6.6 mg CH 4-C m−2 day−1）和森林植被（29.8 ± 10.0 mg CH 4-C m−2 day−1）。扩散CH 4通量也表现出明显的季节性，不同的生态系统之间的季节模式。森林植被和混合棕榈沼泽的旱季排放量（分别为47.2 ± 5.4 mg CH 4-C m−2 day−1和85.5 ± 26.4 mg CH 4-C m−2 day−1）明显高于雨季排放量（分别为6.8 ± 1.0 mg CH 4-C m−2 day−1和5.2 ± 2.7 mg CH 4-C m−2 day−1）。与此相反，森林（短杆）植被和M。flexuosa棕榈沼泽则表现出相反的趋势，旱季的通量分别为9.6 ± 2.6和25.5 ± 2.9 mg CH 4-C m−2 day−1，而雨季的通量分别为103.4 ± 13.6和53.4 ± 9.8 mg CH 4-C m−2 day−1。这些不同的季节趋势可能与雨季森林植被和混合棕榈沼泽的水位非常高（> 1米）有关，这可能限制了CH 4在土壤-大气界面的迁移。扩散的N2 O通量非常低（0.70 ± 0.34 µg N2 O-N m−2 day−1），并且在不同生态系统或季节之间没有显著差异。我们的结论是，泥炭地在PMFB是大的和区域重要的大气CH 4的来源，需要更好地考虑在区域排放清单。与此相反，N2 O通量是可以忽略不计的，这表明该地区并没有作出重大贡献，区域大气预算的N2 O。不同的季节性模式之间的植被类型的CH 4通量挑战我们的基本假设的控制CH 4通量在热带泥炭地，并强调需要更多的过程为基础的测量在高水位期间。
Abstract. The Amazon plays a critical role in global atmospheric budgets of methane (CH4) and nitrous oxide (N2O). However, while we have a relatively good understanding of the continental-scale flux of these greenhouse gases (GHGs), one of the key gaps in knowledge is the specific contribution of peatland ecosystems to the regional budgets of these GHGs. Here we report CH4 and N2O fluxes from lowland tropical peatlands in the Pastaza–Maranon foreland basin (PMFB) in Peru, one of the largest peatland complexes in the Amazon basin. The goal of this research was to quantify the range and magnitude of CH4 and N2O fluxes from this region, assess seasonal trends in trace gas exchange, and determine the role of different environmental variables in driving GHG flux. Trace gas fluxes were determined from the most numerically dominant peatland vegetation types in the region: forested vegetation, forested (short pole) vegetation, Mauritia flexuosa-dominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Diffusive CH4 emissions averaged 36.05 ± 3.09 mg CH4–C m−2 day−1 across the entire dataset, with diffusive CH4 flux varying significantly among vegetation types and between seasons. Net ebullition of CH4 averaged 973.3 ± 161.4 mg CH4–C m−2 day−1 and did not vary significantly among vegetation types or between seasons. Diffusive CH4 flux was greatest for mixed palm swamp (52.0 ± 16.0 mg CH4–C m−2 day−1), followed by M. flexuosa palm swamp (36.7 ± 3.9 mg CH4–C m−2 day−1), forested (short pole) vegetation (31.6 ± 6.6 mg CH4–C m−2 day−1), and forested vegetation (29.8 ± 10.0 mg CH4–C m−2 day−1). Diffusive CH4 flux also showed marked seasonality, with divergent seasonal patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher dry season (47.2 ± 5.4 mg CH4–C m−2 day−1 and 85.5 ± 26.4 mg CH4–C m−2 day−1, respectively) compared to wet season emissions (6.8 ± 1.0 mg CH4–C m−2 day−1 and 5.2 ± 2.7 mg CH4–C m−2 day−1, respectively). In contrast, forested (short pole) vegetation and M. flexuosa palm swamp showed the opposite trend, with dry season flux of 9.6 ± 2.6 and 25.5 ± 2.9 mg CH4–C m−2 day−1, respectively, versus wet season flux of 103.4 ± 13.6 and 53.4 ± 9.8 mg CH4–C m−2 day−1, respectively. These divergent seasonal trends may be linked to very high water tables (> 1 m) in forested vegetation and mixed palm swamp during the wet season, which may have constrained CH4 transport across the soil–atmosphere interface. Diffusive N2O flux was very low (0.70 ± 0.34 µg N2O–N m−2 day−1) and did not vary significantly among ecosystems or between seasons. We conclude that peatlands in the PMFB are large and regionally significant sources of atmospheric CH4 that need to be better accounted for in regional emissions inventories. In contrast, N2O flux was negligible, suggesting that this region does not make a significant contribution to regional atmospheric budgets of N2O. The divergent seasonal pattern in CH4 flux among vegetation types challenges our underlying assumptions of the controls on CH4 flux in tropical peatlands and emphasizes the need for more process-based measurements during periods of high water table.